Winter 2022-2023 Promises Plenty of Mid Season Mayhem

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Mainly Rain Likely Thursday Into Early Friday 

Some Snow Possible Across Northern Sections

While there continues to be some signs of change in a season that seemingly manufactures ways to resist snow and cold throughout the forecast area, the next system poised to impact the area late this week does not appear destined to be any different.

 

The Synoptic Situation:

Once concept that has not been at all foreign to the 2022-2023 winter season has been deep, closed 500mb lows across the western US and midwest, which in conjunction with the notable lack of antecedent cold air, has been the reason for relative dearth of snowfall across the area. This week does not appear to be any different in that regard.

On Thursday morning yet another deep H5 low is forecast to be barreling to the northwest, through the midwest and towards the Great Lakes.

 

However, as potentially a sign of the changes that are underway across the hemisphere, the system encounters an increasing amount of resistance with latitude by way of confluence stationed over southern Canada.

 

This forces the energy to weaken and sheer of to the east, which mitigates the degree of warming that would have otherwise taken place across the northeast.

 

This results in the core of the mid level energy sliding on an ESE trajectory through New York state and across southern New Hampshire.

 

 

It is along and just to the north of this track where the heaviest snowfall totals will be observed, as warm air advection will maximize lift to enhance precipitation without the precipitation actually transitioning to sleet and rainfall.

 

Expected Storm Evolution:

Precipitation should break out as mainly rain, with potentially a mix of snow at the onset in hills of NW Connecticut around the time of the Thursday AM commute before a change to rain.

 

Rain then overspreads the remainder of the region by Thursday afternoon, with snow possible in the Berkshires.

 

There is a chance that precipitation may transition to a period snowfall Thursday evening to the north of the Mass pike, and especially near the NH/VT borders, as evaporative cooling takes place.

 

 

Before tapering off early Friday morning.

 

It may be wise to plan for extra time during the Thursday evening and Friday morning commutes to the north of the Mass pike, as a precaution, but amounts should be light overall.

 

First Call:

 

Final Call will be issued on Wednesday-

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Final Call for Two-Pronged Storm Thursday-Friday 

Mixed Bag with Most Snow North on Thursday; Light Snows Friday

There continues to be some signs of change in the longer term of a season that seemingly manufactures ways to resist snow and cold throughout the forecast area,  and if nothing else, the next system poised to impact the area late this week looks to serve as a reminder that wintry precipitation types are in fact still possible across the region.

 

The Synoptic Situation:

Once concept that has not been at all foreign to the 2022-2023 winter season has been deep, closed 500mb lows across the western US and midwest, which in conjunction with the notable lack of antecedent cold air, has been the reason for relative dearth of snowfall across the area. This week does not appear to be any different in that regard.

On Thursday morning yet another deep H5 low is forecast to be barreling to the northwest, through the midwest and towards the Great Lakes.

 

However, as potentially a sign of the changes that are underway across the hemisphere, the system encounters an increasing amount of resistance with latitude by way of confluence stationed over southern Canada.

 

This forces the energy to weaken and sheer of to the east, which mitigates the degree of warming that would have otherwise taken place across the northeast.

 

This results in the core of the mid level energy sliding on an ESE trajectory through New York state and across southern New Hampshire.

 

 

It is along and just to the north of this track where the heaviest snowfall totals will be observed, as warm air advection will maximize lift to enhance precipitation without the precipitation actually transitioning to sleet and rainfall. Additionally, as the core of the upper level energy traverses the are on Friday, a second round of precipitation should break out across the area and that looks to primarily fall in the form of snowfall.

 

 

 

Expected Storm Evolution:

The storm system will occur in two parts.

 

Round 1

The first portion on Thursday will be triggered by the lift associated with warm air advection from the  southwest in the upper levels of the atmosphere, as the upper leve low approaches from the west. Precipitation from round one should break out as mainly rain on Thursday afternoon, with potentially a mix of snow at the onset in hills of NW Connecticut before a change to rain.

 

Precipitation will overspread the rest of the area by Friday evening as primarily rainfall, with the exception of the northern third of the state north of approximately route 2, where the Thursday evening commute may be somewhat problematic.

 

The as warm air advection wanes in the latter stages of round one, the snow will begin to collapse back to the south towards the Mass pike area before tapering to a period of drizzle early Friday morning.

 

 

The break in the precipitation will fortuitously coincide with the Friday AM commute, however, motorists should be mindful of potentially dangerous freezing drizzle over the interior.

 

Round 2

Light snowfall should begin to break out in association with the trailing upper level energy during round two on Friday afternoon, which may cause some issues for the evening commute with ill timed light additional accumulations.

 

This is when locales south of the route two corridor will see the forecast accumulations before it begins to taper off later in the evening.

 

 

And end entirely prior to midnight.

 

Final Call:

First Call:

Issued 12pm Tuesday, January 17

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Very Active Pattern Favors Multiple Storm Threats Final Week of January: First Call for Monday

As a sign of an active regime that is replete with a consistent flow of Pacific energy, a storm system for Monday is already coming into focus here on the eve of the storm to begin the weekend later tonight an into tomorrow.

 

Synoptic Situation:

A consequence of the active Pacific jet frequently supplying energy onto the west coast is that it teleconnects to higher heights over the southeast. Thus while we have a very active storm track due to a Pacific assembly line of systems, there will be a tendency for them to de-amplify as they approach the east coast.

 

The system approaching on Monday is no different. Indeed, the consistent feed of energy spilling over the AK EPO ridge and onto the west coast pumps up heights over the southeastern US and attenuates the storm due to the compressed nature of the flow between the southeast ridge and the confluent flow over SE Canada.

 

While the lack of high latitude blocking and southeast ridge make it likely that a strong and phased system will track inland, the compressed nature of the flow in between render it less likely that a system will reach the coast without undergoing rather significant attenuation. The nuances of precisely how each system interacts with this pattern will determine the exact track and where the rain snow line will be, but what is more certain is that this does not initially appear to be a pattern favorable for major east coast snowstorms.

This same situation also applies for the follow up wave later in the week, which also attenuate on approach.

 

The bottom line is that the general theme will be moderate sized storms that will favor mixed precipitation and more snow inland, as well as to the north.

 

Expected storm evolution for Monday:

Precipitation should begin to break out late Monday evening over western New England, s potentially snow and sleet over the Berkshires and NW Connecticut hills with rain elsewhere.

 

 

Then by the predawn hours, snow and sleet become relegated to the northern Berkshires, as a rather mild antecedent airmass in conjunction with a southwest flow aloft cause the mid levels of the atmosphere to warm even further.

 

 

Ordinarily in mid January, mid level low pressure tracking just south of Boston would still mean significant snows for much of the area. But in this instance, the low is tracking close enough given the mild antecedent airmass as to induce enough warm air advection to ensure primarily rainfall for the bast majority of southern New England, save for the northern Berkshires.

However, as the low begins to pass by Nantucket islands, winds should begin to back more out of the north. This will slightly colder air to being working back to the south and a transition back to snowfall of any mixed precipitation will occur over the Berkshires around the time of the Monday AM commute.

 

 

And then the precipitation may potentially end as a period of snow showers across the rest of the region during the midday Monday period, however, the same northerly winds that are responsible for the colder air advection are also transporting drier air into the region.

 

What this entails is that backside snowfall is usually overdone on guidance, especially in the lower elevations, thus any appreciable light accumulations on the backside of the storm system during the day on Monday will be confined to the Worcester hills.

 

 

First Call:

 

Final Call will be issued on Sunday-

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Thursday-Friday January 19-20 Verification

Largely Successful Forecast

Here is the Final Call snowfall map for yesterday's storm:

 

Versus observed snowfall totals:

 

 

The system was forecast very well, with the notable exception of that fact that snow showers on Friday had slightly more difficulty accumulating than anticipated. This the southern periphery of the 1-3" zone should not have extended south of the Mass pike at all, but otherwise this was a a very accurate forecast.

 

Final Grade: B+

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Final Call for Sunday Night-Monday 

Potentially Similar Outcome to Friday

Synoptic Situation:

 

 

A consequence of the active Pacific jet frequently supplying energy onto the west coast is that it teleconnects to higher heights over the southeast. Thus while we have a very active storm track due to a Pacific assembly line of systems, there will be a tendency for them to de-amplify as they approach the east coast.

 

The system approaching on Monday is no different. Indeed, the consistent feed of energy spilling over the AK EPO ridge and onto the west coast pumps up heights over the southeastern US and attenuates the storm due to the compressed nature of the flow between the southeast ridge and the confluent flow over SE Canada.

 

European forecast from Friday for Monday evening:

While the lack of high latitude blocking and southeast ridge provide a pathway for a strong and phased system to track inland, the compressed nature of the flow in conjunction with the confluence to the north work to force the system to initially attenuate and ultimately redevelop along the coast. The primary difference from the First Call issued on Friday is that said redevelopment now appears to take place slightly faster and further to the south.

 

European forecast from Saturday evening for Monday evening:

 

This may cause  a period or protracted snowfall along the coast during the say on Monday not at all dissimilar from this past Friday, during which light accumulations occurred.

Expected storm evolution for Sunday Night & Monday:

 

 

Precipitation should begin to break out late Monday evening over western New England, s potentially snow and sleet over the Berkshires and NW Connecticut hills with rain elsewhere.

 

Then by the predawn hours, snow and sleet become relegated to the Berkshires and Worcester hills, as a rather mild antecedent airmass in conjunction with a southwest flow aloft due to the decaying primary cause the mid levels of the atmosphere to warm even further.

 

Ordinarily in mid January, mid level low pressure tracking just south of Boston would still mean significant snows for the vast majority of the area. But in this instance, the low is tracking close enough given the mild antecedent airmass as to induce enough warm air advection to ensure primarily rainfall across southern and southeastern third of New England.

 

 

 

However, as the low begins to pass by Nantucket island, winds should begin to veer more out of the north as the coastal redevelopment intensifies. This will cause slightly colder air to be entrained into the system and a transition of any residual mixed precipitation to snowfall will occur over first over the Worcester hills just after the Monday AM commute.

 

And then into the Boston area by midday on Monday.

It is during Monday afternoon that storm accumulations will take place the southern and eastern portion of the forecast area in a burst of snowfall.

 

 

Before tapering off Monday evening and ending by midnight.

 

Final Call: 

 

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Mainly Rain Likely Wednesday Evening Into Thursday

Light Snow Accumulations Possible

Synoptic Situation:

In what has been a common theme during the boreal 2022-2023 winter season, yet another instance of energy amplifying well to the west, which causes any snowfall to rapidly transition to rain as the high pressure slides off of the coast.

 

However, in contrast to some other instances this season, there is some antecedent cold that needs to be displaced, which will result in a light snow for a portion of the region.

 

Expected storm evolution for Wednesday Night & Thursday:

Snowfall should begin to breakout over far southwestern portions of New England by early afternoon on Wednesday.

 

Snowfall will overspread the rest of the region over the course of the afternoon and begin to transition to rainfall near the south coast before evening.

 

 

And then rapidly mix with and change to rain across the remainder of the region by midnight.

 

Before ending Thursday morning.

 

First Call: 

 

One more look on Wednesday.

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Snowfall Slightly Heavier Than Forecast on Monday

Here is the Final Call map for Monday:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Versus actual verified snowfall:

 

 

Snowfall was heavier than forecast across especially eastern areas, since the secondary storm intensified a bit faster than expected upon exit. This 3-6" would have been the more appropriate range across eastern Mass, with 1-3" across southeastern Mass.

 

Final Grade: C

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Final Call for Snow to Rain Wednesday Night Into Thursday

No major Changes; Minor Snowfall Accumulations Expected

Synoptic Situation:

There are no significant changes for the forecasting rationale expressed in the First Call on Monday. In what has been a common theme during the boreal 2022-2023 winter season, energy is currently  amplifying well to the west, which coupled with a rather mild antecedent airmass, causes any snowfall to rapidly transition to rain as the high pressure slides off of the coast and even milder air floods the region.

 

Expected storm evolution for Wednesday Night & Thursday:

Snowfall should begin to breakout over far southwestern portions of New England by early afternoon on Wednesday.

 

 

Snowfall will overspread the rest of the region over the course of the afternoon and begin to transition to rainfall across much of Connecticut, Rhode Island and south eastern Mass by the evening hours

 

 

And then rapidly mix with and change to rain across the remainder of the region by midnight.

 

 

Temperatures will rise overnight as the low moves inland and heavy rain continues with potential ponding in poor drainage areas, especially in locations to the north with relatively deep snowpack. 

 

 

 

Then the rain tapers off amidst blustery conditions Thursday morning.

 

 

Final Call: 

 

First Call, issued Monday, January 23 at 11am:

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Here is the Final Call snowfall forecast map:

 

Versus what actually accumulated:

 

 

Snowfall amounts were slightly over forecast, as the initial area of lift was weaker than forecast, which resulted in less substantial snowfall than anticipated before the changeover to rainfall last night. The 2-5" forecast zone over the Berkshires, northern Worcester county hills and southern new Hampshire verified as 1-3". And the 1-3" area to the south verified as a trace to 1".

 

 

Final Grade: C

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Very Active January Much Milder Than Forecast

Cold Start to February Belies the Overall Tenor of the Month

The month of January verified as several degrees above average across the northeastern US:

 

This was clearly much warmer than the January forecast, which was near normal:

 

One reason for the terrible forecast was the very active Pacific jet stream, which although it was expected to be prominent at certain points over the course of the season and supply a very active storm track, it was was more of a factor than anticipated due to the fact that the polar jet never became involved.

This is apparent when looking at the actual H5 composite versus what actually transpired.

 

Cold Unavailable for Active Storm Track

It is very apparent froM the Eastern Mass Weather January 2023 H5 forecast composite that the polar domain was expected to interact with the aforementioned Pacific parade of storm systems.

 

However, high latitude blocking never rematerialized as forecast, after the original episode in December. 

 

 

It is important to note that interestingly enough, there was in fact cold air available, as evidenced by the mean negative AO value for the month.

 

 

 

But since the storm track remained inland and there was no cold air available, it is easy to discern why much of the east coast experienced little to no snowfall, despite such an active storm track.

When considering why that was the case it is important to remain mindful of the fact that nothing within the global atmosphere occurs in a vacuum. It is apparent from the January 2023 annotation above that the NAO remained decidedly positive throughout the month of January.

 

 

This combined with some subtle nuances with respect to the Pacific pattern acted to ensure that storms tracked inland from the coast.  And perhaps more importantly, trap the main hemispheric reservoir of cold in Siberia, thus preventing it from being entrained into the active parade of storm systems. 

Here is the PNA plot for the month of January:

 

While it did in fact average positive, as forecast, the higher heights were focused in the western portion of the PNA domain and off of the west coast, which only served to augment troughing along the west coast. This configuration largely mimicked the RNA pattern of December, however, unlike December, January featured a +NAO, which worked in conjunction with the western biased +PNA to ensure an inland storm track. And given the fact that there was no Aleutian ridging or cross polar flow to tap the cold supply in Siberia, there was very little antecedent cold to allow for southwest flow events or front end snowfall for the coast. 

 

January 2023:
 

 

 

This is not at all unlike the evolution of January 2002, which was a double weighted year in the seasonal analog forecast composite.

 

January 2002:

Thus while the month did feature some el nino like qualities, as anticipated, the cold air was never able to link with the active storm track. 

The latter was an unexpected occurrence.

The main question now moving forward into February becomes is there any hope for sustained winter east...

 

Mild February Remains on Track after Frigid Start

February Analogs: 1955, 1956, 1975, 1976, 1984, 1986, 1989, 1990, 1997, 2001, 2008, 2011,2017, 2018, 2022

Despite the deviation from the forecast with respect to January, the thought process with respect to February has changed little since November.

There should be an intense, albeit brief, bout of arctic air as a polar vortex descends on the region this weekend. This will be accompanied by very dangerous wind chills, so dress accordingly if outside.

 

 For the balance of the month, the vast majority of snowfall this month will come from overrunning and warm air advection processes. The pattern will continue to be particularly hostile to major east coast snow storms.

 

 

 

 

However, there should be a transition to a more traditional la nina like pattern in which a cold air will be in supply over Canada.

 

Although cold will flirt with the region during episodes of poleward Aleutian ridging at time this month,  it will enter out west first and then slowly bleed south and east in a modified fashion with prominent -PNA present. NAO blocking should remain absent and the polar vortex intact, thus precipitation issues will continue to be prominent outside of northern New England.

Thus there should be some light to moderate snowfall threats throughout the month.

Here is the latest CFS guidance, which conveys this general sentiment of a "gradient" like, overrunning pattern.

 

 

 

 

 

This is in general agreement with the forecast composite from last fall.

 

 

Overall, the pattern should vacillate between a traditional "modoki" la nina like pattern, which is very mild over the east, and a gradient type of pattern. The latter features a pronounced reservoir of cold over the source region despite a lack of blocking, similar to the 1973-1974, 1975-1976, and 2007-2008 seasons.

 

Here we can see that after the initial arctic plunge this weekend, the MJO filtered forcing assumes a modoki la nina like regime, which will coincide with the very mild pattern (much like the February forecast composite) that will ensue once the arctic shit departs.

 

 

What is also apparent is that there may be a some potential for a bout of wintry weather near mid month, as the modoki forcing regime may abate, as implied in the filtered MJO plot above. Whether or not that happens or not is dubious. There is more support from the GFS camp, which eventually takes the MJO wave into the more favorable phases.

 

 

 

But the European suite decays the wave in phases 4 and 5, which are very mild for the east coast.

 

 

The trend this season given the well coupled la nina has been for the MJO to excite in phases 4-6, and for for guidance to over amplify it in phases 7-3, which are cooler for the eastern US. Thus this is the outcome that should be favored. However, this should be monitored given that the MEI continues to elevate, as the cool ENSO influence in the atmosphere wanes. Needless to say, somewhat cooler and more wintry weather is likely to return around mid month.

 

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Winter to Potentially Return Later in February

Major Disruption of Stratosphere to Ensue 

There is a growing school of thought that winter is essentially over and that this season will end as one of the mildest and least snowy on record across much of the region. And while that still may be the case, there is reason to believe that winter is not destined to end quietly. Indeed, it was it was expressed in the Eastern Mass Weather Winter Outlook this past November that the latter portion of the season was at an elevated risk for a significant disruption to the polar vortex, which could result in one more round of high latitude blocking. And is now all but a certainty that this will indeed occur.

 

Currently the polar vortex remains very stout and centered, which is keeping the supply of cold constricted over the arctic:

 

 

However,  the weakening of the zonal mean wind anomaly over the polar stratosphere after mid month is very evident on the the European guidance.

 

 

This weakening of the vortex results in a great deal of warming of the polar stratosphere by 2/19 on both the European:

 

 

And the GFS suite:

 

However, neither ensemble suite currently reflects this polar disruption in the pattern very well, as evidenced by the forecast H5 anomaly for that same time frame being void of high latitude blocking.

 

European:

 

 

GEFS:

 

 

 

The GFS ensemble maintains this disruption of the polar vortex through the end of the month.

 

 

With still no notable reflection in the overall pattern.

 

 

This is possible given the fact that the manner in which major disruptions of the polar vortex do, or do not manifest themselves into the pattern can be difficult to predict. And it is possible that the cold is sent into Siberia as it was for much of  January. However, there maybe some early signs of a more ominous end of the month beginning to emerge in the form of a descent of both the AO and NAO.

 

 

 

 

 

 

Thus the more likely scenario given analog preference is that the ramifications of said disruption will be slow to materialize on guidance and that ultimately it will in fact influence the pattern to assume a more wintery character to at least some degree.

 

Potential Late Season Analog

There are signs of this in the longer range European weekly product, which is now signaling strong blocking ultimately materializing during the last week of February, which resembles one of the primary Eastern Mass Weather 2023 seasonal analogs:

 

 

 

 

This is transition on the European weekly product is a progression that is very similar to that which occurred during February 1956, which is both one of the five primary ENSO analogs and a member of the favored RNA style extra pacific composite discussed in the winter outlook.

 

The season has indeed been a viable analog to date, including a month of December which featured a strong bout of NAO style blocking that resulted in very little snowfall for the region.

 

What can be gleaned from this analog is that the RNA pattern is very likely to persist, so the ability of cold to return to the eastern US for any length of time will depend on whether of not the disruption of the polar vortex can trigger another episode of high latitude blocking. Ultimately what may determine whether or not these changes in the polar stratosphere translate to the surface enough to ensure that the end of winter 2023 will be eventful is whether or not la nina has weakened enough to finally allow a coherent MJO wave entry into phases 7 and 8. But in the mean time, history has taught us that it would be unwise to write it off entirely. In the mean time, enjoy the pleasant weather and get outside before a potentially active late February and first half of March.

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Increasingly Stormy and Somewhat Colder Pattern Implies Stronger Finish to Mild Winter of 2022-2023

Polar Vortex Initially Extends South to Begin Major Disruption

Last week, Eastern Mass Weather used teleconnector convergence to focus on the period between February 20-23 for the next significant winter storm threat, which coincides with the extension of the polar vortex to the southeast during the initial stages of a major disruption. Confidence has continued to increase this week, as there is a very good consensus that the polar vortex will begin to encroach on the northern edge of the southeast ridge, thus suppressing the storm track somewhat and introducing colder air into the equation on the northern flank.

EPS Mean next Thursday 2/24 evening:

 

GEFS Mean next Thursday 2/24 evening:

 

 

EPS Mean Sunday 2/26: 

GEFS Mean Sunday 2/26:

 

While some wintry precipitation is likely across the region, precipitation type issue are likely to be very prevalent, as the mid level area of low pressure is likely to ride the boundary between the colder air to the north, over northern New England, and the milder air to the south.

 

 

This means that the boundary may initially set up in the general vicinity of the Mass pike for the first event next week, before potentially allowing the milder air to fight back slightly further to the north for the follow up event during the final weekend of February in the event that the first wave is not potent enough to compress the flow further to the south.

 

 

Thereafter, as we look towards the month of March, there is growing evidence to suggest that major blow that the polar vortex takes at the stratospheric level during the month of February will translate down to the surface.

 

Development of High Latitude Blocking Likely to Conclude February

There is growing evidence to suggest that the active ending to the 2022-2023 winter season that was suggested by Eastern Mass Weather last fall is indeed going to come to fruition. Note the GEFS forecast using ECMWF data provided by @WorldClimateSvc, which illustrates the propagation of the significant warming and subsequent disruption of polar vortex down fro the stratosphere to the troposphere.

This forecast is supported by the research of @zd1awarence, @splillo and @SimonLeeWx, courtesy of DrAHButler, which implies that SSW events most successfully propagate downward and result in periods of negative NAO when the MJO wave is active and/or in phases 5-7.

 

The MJO is currently moderately active in phase 6 and transitioning to phase 7.

 

If correct, while it does not guarantee major snowfall, as seen during the month of December, it would entail a redevelopment of the NAO blocking that took place early in the season. The main question, aside from the synoptic nuances that dictate snowfall, would be how long it lasts.

The European guidance implies that the vortex would remain dysregulated throughout the month of March.

 

While the GFS ensemble implies a recovery during the second half of the month, which is when climo becomes rather hostile for snowfall throughout the forecast area, regardless.

 

 

Here is the warming that is currently getting underway in earnest:

 

Note that the initial effect of the disruption is for the vortex to relocate further southeast, which results in the wintry threats next week.

 

Thereafter, during the final days of February, the vortex begins to weaken much more as the warming propagate lower:

 

EPS: 

GEFS: 

EPS: 

GEFS: 

 

And as March begins, the vortex is largely decimated with a large and well coupled warm bubble remaining over the arctic at all levels of the atmosphere.

 

10mb (stratosphere): 

50mb (Troposphere): 

 

Resultant Greenland blocking at 500mb: 

 

 

One potential general analog to this sequence of events is February into March 1956, which was both one of the Eastern Mass Weather primary ENSO analogs and one of the favored extra tropical Pacific RNA dominant analogs.

 

First half of February 1956: 

First half of February 2023: 

Latter February 1956: 

12/1/2022 - 2/13/2023: 

 

12/1/1955 - 2/13/1956: 

 

 

Stay tuned for more on this potential evolution as we near the month of March. And updates on next week's storm threat(s) over the coming days.

 

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Messy Thursday on Tap: First Call

Some Snowfall Accumulation Likely North; Ice Threat South

Synoptic Situation:

It was explained on Eastern Mass Weather last week how the final week of February would be turning more wintry due to the southward pressing of the polar vortex, which begins to encroach on the territory of the south east ridge. This battle is very apparent as a lobe of energy breaks off from the massive and seemingly semi permanent western US trough towards mid week.

 

The lobe of energy attenuates as it is forced through the compressed flow between the PV to the north, and the SE ridge to the south on Wednesday into Thursday, as it approaches the area.

 

 

The PV continues to edge to the southeast and encroach on the area as the storm system moves though the area, thus at some point during the storm, arctic air will be drawn back to the south. This will complicate the forecast.

 

Anticipated Synoptic Evolution:

Very little if any snowfall will occur across the southwestern half of Connecticut, as precipitation will begin later Wednesday evening as a mixture of sleet and rain.

 

This is due to the track of the mid level system drawing in warmer air aloft.

 

Any snowfall in the Mass pike region rapidly transitions to sleet by shortly after midnight with only very light accumulations of snowfall, beforehand, as warmer air aloft continues to overspread the area on a southwest flow.

 

 

The Thursday AM commute will be hazardous to the north and west of Boston, as sleet continues to fall to the north with perhaps a mixture of sleet and freezing rain to the west. The immediate Boston area and points southeast should be raining during the commute. However, all areas should be messy and plenty of extra time will likely be needed.
 

Conditions should improve throughout the immediate Boston area during Thursday AM, however, arctic air will begin to filter back towards the area from the northeast around midday.

 

This could cause roadways to ice over again during early to mid afternoon, from northeast to southwest.

 

This will especially be a hazard to the north of the Mass pike, will residual precipitation will remain into mid afternoon.

 

 

Allow plenty of extra time for the evening commute, as well, as area roadways are still likely to ice over despite the last of the precipitation moving out to the north.

 

 

FIRST CALL:

 

Final Call will be issued on Tuesday-

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Final Call for Mess Thursday Commutes: No Real Changes

Some Snowfall Accumulation Likely North; Ice Threat South

Synoptic Situation:

It was explained on Eastern Mass Weather last week how the final week of February would be turning more wintry due to the southward pressing of the polar vortex, which begins to encroach on the territory of the south east ridge. This battle is very apparent as a lobe of energy breaks off from the massive and seemingly semi permanent western US trough towards mid week.

 

The lobe of energy attenuates as it is forced through the compressed flow between the PV to the north, and the SE ridge to the south on Wednesday into Thursday, as it approaches the area.

 

 

The PV continues to edge to the southeast and encroach on the area as the storm system moves though the area, thus at some point during the storm, arctic air will be drawn back to the south. This will complicate the forecast.

 

Anticipated Synoptic Evolution:

Very little if any snowfall will occur across the southwestern half of Connecticut, as precipitation will begin early Wednesday evening as a mixture of sleet and rain.

 

 

 

 

This is due to the track of the mid level system drawing in warmer air aloft.

 

 

 

Any snowfall in the Mass pike region rapidly transitions to sleet by shortly after midnight with only light accumulations of snowfall, beforehand, as warmer air aloft continues to overspread the area on a southwest flow.

 

 

 

The Thursday AM commute will be hazardous to the north and west of Boston, as sleet continues to fall to the north with perhaps a mixture of sleet and freezing rain to the west. The immediate Boston area and points southeast should be raining during the commute. However, all areas should be messy and plenty of extra time will likely be needed.
 

 

 

Conditions should improve throughout the immediate Boston area during the early morning hours of Thursday AM, however, arctic air will begin to filter back towards the area from the northeast around the time of the morning commute.

 

 

This could cause roadways to ice over again during early to mid morning, from northeast to southwest.

 

 

This will especially be a hazard to the north of the Mass pike, will residual precipitation will remain into mid afternoon.

 

Allow plenty of extra time for both the morning and evening commutes, as area roadways are still likely to ice over despite the last of the precipitation moving out to the north. The AM commute especially north and west of Boston, but it should even be slippery near the post for the afternoon drive.

 

 

 

FINAL CALL: 

No changes from First Call map issued on Sunday.

 

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March to Begin Like Lion

High Impact Winter Event Increasingly Likely to Begin March

There is a large contingent of meteorology hobbyists, and perhaps even professionals, who have resigned themselves to the fact that 2023 is going to be the year without a winter. And in a season that has featured one of the warmer January and February periods on record, as well as a near historic dearth of snowfall, it is difficult to not allow emotion to compromise objectivity and to assume that the status quo will carry the region into spring. However, mother nature is well aware of how assumptions often make one look and as Eastern Mass Weather has opined dating back to last fall, this assumption is unlikely to be much different. In a season that hasn't lacked for reasons not to snow, the month of December failed to produce any significant snowfall for the region despite one of the stronger NAO blocks in recent memory. It was expressed in the Eastern Mass Winter Outlook this past November that instances of severe early season high latitude blocking usually reappear later in the season and that this would likely take place early on in the month of March. This pattern now looks to materialize on the heals of the SSW that took place last week. 

The European guidance is strongly supportive of a very major winter storm from February 28 through March 1:

 

 

Note the dipole of the negative NAO block and associated 50/50 low providing enough resistance to prevent the strong pocket of energy in the midwest from traveling up through the Great Lakes, and instead to the east to the south of Long Island.

The GEM suite depicts a similar evolution:

 

 

However,  there continues to be dissent from the GFS suite, which supports a slightly less assertive NAO bock and 50/50 low that is displaced to the east. This does not allow the coastal energy to become dominant until the system is well off of the coast.

 

 

 

While either solution is plausible,  the prudent course of action is to expect the most significant winter storm thus far this season. And remain mindful that given the pattern that is modeled to materialize on the more highly skilled European suite, the most impactful winter storm thus far this decade is a legitimate possibility if not yet a likelihood. This is an evolution quite similar to the 1956 analog discussed just last week.

Expect a great deal more clarity for the update this weekend-

[rimetree]

Winter 2022-2023 Promises Plenty of Mid End of Season Mayhem

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1 hour ago, rimetree said:

Winter 2022-2023 Promises Plenty of Mid End of Season Mayhem

Yea...that is hole in the effort thus far. 

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Very Skillful Thursday (2/23) Forecast

Not much to analyze in the aftermath of this system, as the Eastern Mass Weather Final Call was very accurate overall.

 

Final Call:

 

 

 

Reality:

 

 

The only minor flaw is that perhaps the southern periphery of the 1-3" zone could have been slightly further to the north, over the Mass border from Connecticut and Rhode Island.

 

Final Grade: A

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First Call for Significant But Not Major Tuesday Snowfall 

Subtle Changes at High Latitudes Limit Potential

Eastern Mass Weather began to sound the alarms on Wednesday for a March lion that had the potential to be one of the larger storms of this decade, and at the very least the largest of this season. It now can confidently state that it will be the latter and here is why.

 

The Synoptic Situation:

What has not changed is that a very vigorous piece of energy still looks to eject out of the southwestern US on Monday and head towards the area.

 

 

However, it now appears as though the system will run out ahead of the polar vortex (PV) that had been trying to feed into the back side on some of the guidance earlier this week. 

 

 

What has also changed is that heights over the southeastern US are slightly higher than originally modeled, which creates more of a shearing compressed flow and causes the system to attenuate on approach. 

 

 

This is an enormous change because it now means that the system will weaken a great deal on approach, instead of intensifying due to phasing with PV energy feeding into the backside.

The reason why is apparent when comparing the last night's GFS model image valid Wednesday AM with the image from the same time from Euro ensemble suite on Wednesday afternoon.

 

 

Note 4 subtle, but crucial differences:

1) The blocking over Greenland is now weaker and further east, which causes.....

2) The 50/50 low portion of the north atlantic dipole to also be displaced to the east, which causes...

3) The lead system ejecting out of the southwest and approaching the northeast to run out of ahead the PV energy that not feed into the backside, as it looked as though it may earlier in the week.

4) Finally, the NAO block being weaker and slightly further east (1) allows for slightly stronger southeast ridging, which creates more of a shearing compressed gradient between the lower heights associated with the cold over southeastern Canada. 

The GFS guidance had a much better handle on this earlier this week.

 

Note how much more similar this forecast chart from  Wednesday is to what is currently modeled

 

Thus instead of phasing tremendous energy into the backside of the system on approach, it is remaining discrete and attenuating in a compressed flow. The difference is that some storm now becomes merely some storm that will be vanquished from memory faster than a meager snowpack under every increasing March irradiance.

 

Expected Storm Evolution:

Snow will overspread southwestern New England late Monday evening.

 

 

And the rest of the region during the overnight and predawn hours early Tuesday AM.

 

 

Its possible that some sleet may mix with snowfall near the south coast of Connecticut towards dawn on Tuesday and limit accumulations somewhat, but precipitation should fall as primarily snowfall in an area that has seen just about none thus far this season.

 

 

 

Another ramification of the blocking displaced to the east is that the primary low over ontario is allowed to remain dominant for a longer period of time, which causes an onshore flow that could limit accumulations somewhat over eastern areas. This is especially true over the cape and islands, where snowfall will ultimately change to rain.

 

 

Precipitation should taper off by tuesday evening, as the secondary low becomes dominant and pulls away to the east.

 

 

First Call:

 

Final Call will to be issued on Monday-

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Mild & Well Forecast February; More Wintry March Likely

The pattern during the month of February overall, was expected to vacillate between a traditional "modoki" la nina like pattern, which is very mild over the east, and a gradient type of pattern. The latter features a pronounced reservoir of cold over the source region despite a lack of blocking, similar to the 1973-1974, 1975-1976, and 2007-2008 seasons. This is precisely what took place.

Note the similarity between the MJO filtered forcing and the modoki la nina like regime.

 

This makes sense given that the la nina has actually shifted into more of a modoki event as the season has progressed.

 

 

 

Here is the February 1-25 H5 anomaly plot, which is similar to both the modoki and February forecast composite:

 

Versus the forecast February H5 plot:

 

Note the similarities between the actual and forecast save for two differences. Firstly, while there was not expected to be any high latitude blocking this month, the polar vortex ended up even stronger than anticipated, which is likely due to the mid month SSW which will have implications on the pattern during the month of March. Secondly, heights were lower over the southwest than anticipated, likely due to some variations in the western Pacific.

 

Here are the temp anomalies for February 1-23:

 

Versus the February forecast:

 

 

Note again that while the east coast is mild, as forecast, the southwestern US was cooler than forecast.

 

Finally, here are the actual February 1-23 precipitation anomalies:

 

And the forecast February precipitation anomalies:

 

It was dry over portions of the east and southern California with an active storm track through the Pacific northwest.

 

The monthly teleconnections were all well forecast.

 

The AO and NAO both averaged positive:

 

 

 

The extremely positive AO value is not only a reflection of not only the modoki la nina pattern, but also due to the flex of the polar vortex that often takes place during and in the immediate wake of a major disruption, which took place mid month. The initial sign of the disruption manifested itself in the form of a stretched vortex, which is why latter February turned colder across the north. However, the the warming over the polar stratosphere is propagating down to the troposphere.

 Thus it is likely to induce a pro longed period of high latitude blocking, which is already showing up on guidance for at least the first half of the month of March.

 

Forecast for Blockier and More Wintery March Remains Unchanged

The month of March is indeed highly likely to begin as a lion, as one moderate winter storm is likely on Tuesday with the potential for a follow up major system waiting in the wings for Friday.

 

What is a apparent is that a fairly strong NAO block becomes established, which prevents the system from tracking well inland, despite a very deep and negatively tilted trough. The reason for said negative NAO is very evident given the fact that the aforementioned SSW is propagating down to the lower levels.

 

However, while the disturbed PV means that March is unlikely to accrue the positive anomalies that January and February featured, the month is still unlikely to average significant negative temperature anomalies given that the main PV remains on the other side of the globe. This is consistent with both the Eastern Mass Weather forecast composite, which reflects near normal temperature departures:

 

 

As well as current climate guidance that also has temperatures near normal:

CFS forecast March Temp anomalies

EURO forecast March temp anomalies:

 

 

Given that there is high confidence that the month will begin cooler and stormy, the main question is how long said pattern will persist. Given past instances of SSW induced episodes of high latitude, including this past December, the blocking is likely to persist for approximately ten days to two weeks.

 

This is also in accordance with current tropical indicators.

 

Tropical Support for March Blocking

Thus far this season, the MJO has been unable to enter phases 8 and 1 for any length of time given the la nina derived standing wave. However, guidance is strongly indicating that that is about to change, perhaps owed to waning la nina and changing wavelengths.

There exists strong agreement amongst both the European and GFS guidance that the MJO wave is going to amplify  in phase 7 and remain potent as it progresses through phases 8 and 1 during the first half of March.

 

This progression is also evident in the MJO filtered velocity potential forecast, which is a strong indicator of where the forcing (MJO wave) will be positioned.

Note that has the pattern peaking during the second week of March, the forcing reaches the dateline, which is congruent with MJO phase 8.

 

This is logical given that the first major winter storm on Friday is going to occur with the MJO in phase 7 and a western atlantic ridge in place, which is why it likely to have precipitation type issues near the coast.

 

But then the pattern is expect to become more favorable for sustained cold when it peaks in phase 8, during the second week of the month.

 

 

It is reasonable to conclude that this more wintery pattern will persist at the very least through mid March, and there is the potential for longer given the analog of March 1956, which followed a similar progression.

 

 

March H5 anomaly forecast composite:

 

CFS anomaly forecast composite:

 

 

European anomaly forecast composite: 

 

Stay tuned to Eastern Mass Weather for more on individual storm threats both this week and throughout the month of March.
 

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Final Call for Significant Tuesday Snowfall 

Subtle Changes at High Latitudes Limit Potential

Eastern Mass Weather began to sound the alarms on Wednesday for a March lion that had the potential to be one of the larger storms of this decade, and at the very least the largest of this season. It now can confidently state that it will be the latter and here is why.

 

The Synoptic Situation:

What has not changed is that a very vigorous piece of energy still looks to eject out of the southwestern US on Monday and head towards the area.

 

 

However, what has become clear over the course of this week for reasons discussed on Saturday in the First Call is that the system will run out ahead of the polar vortex (PV) that had been trying to feed into the back side on some of the guidance earlier last week. 

 

 

Be that as it may, some this northern stream does attempt to phase in as the system begins to exit the region on Tuesday evening, which may protract the period of precipitation somewhat as slightly colder air filters back into the region around the low on Tuesday evening.

 

Expected Storm Evolution:

Snow will overspread southwestern New England late Monday evening.

 

 

 

And the rest of the region during the overnight and predawn hours early Tuesday AM.

 

 

 

As warmer air is drawn to the north during the predawn hours of Tuesday AM, snow will begin to mix with and possibly and change to rain along the south coast/cape and islands, but precipitation should fall as primarily snowfall over a large area that has seen just about none thus far this season.

 

 

 

The Tuesday morning commute will be highly problematic for the region, as snowfall continues north of the south coast/cape and islands.

 

 

Although much of eastern Mass and southern Connecticut and Rhode Island will continue to see snowfall during the morning hours of Tuesday, and through midday and into the afternoon, onshore flow coupled with an increasingly strong late February sun will significantly slow accumulations in this area.

 

 

 

 

This may especially hamper accumulations over eastern Mass, due to decreasing lift and dynamics as the shortwave attenuates prior to the influx of some northern stream energy.

This is apparent in the soundings across the region.

 

Note how there is significantly stronger lift and more moisture within the -12c to -18c snow growth zone (SGZ) near Hartford, CT.

 

And even to a slightly lesser extent near Springfield, MA.

 

However, note how lift and moisture is not quite as robust within the SGZ in Worcester, MA, which implies that highest amounts in this region are likely to be in the higher elevations of the Worcester hills.

 

By the evening commute, any mixed precipitation over the south coast/ cape and islands should begin to transition back to snowfall, as colder air and a burst of dynamics infiltrates the area as northern stream energy finally begins being ingested as the system pulls away. While this burst of snow will not be of long enough duration to significantly impact accumulations, the timing of it during the evening commute maybe problematic.

 

 

 

 

 

 

Precipitation should taper off by before midnight Tuesday evening, as the secondary low becomes dominant and pulls away to the east.

 

 

 

Final Call:

 

First Call: Issued Saturday 2/25 @5AM

 

Final Call will to be issued on Monday-

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First Call for Friday Winter Storm: Sometimes Guidance is Right for the Wrong Reason

Examining Discrepancies and Potential Errors in Guidance

The month of March is set to begin in an active manner, as advertise. Indeed, fresh on the heels of the system currently impacting the region to end the month of February, another and perhaps slightly more significant winter storm is poised to effect the area on Friday.

 

Synoptic Layout:

A vigorous piece of energy is poised to eject out of the southwestern quadrant of the region on Friday in begin its journey northeast, as depicted below on the GFS guidance.

 

 

The European has modeled the initial intensity of the system very similarly to that of the GFS.

 

 

It is at this early juncture where the discrepancies begin, as the GEM guidance already has the system modeled significantly less intense by early Friday AM than the GFS and Euro.

 

 

Given the fact that the GEM is in outlier, and the GFS and EURO have superior initialization schemes, it is safe to assume that the GEM is likely in error in this respect. This is important to remember moving forward in the forecast.

By just after midnight on early Saturday AM, the GFS has translated the system off to the north east to a position near Lake Erie in a weakened state, as it begins veering more to the east northeast. Intuitively, this make sense when considering the wall of confluent flow that the system encounters, which is resultant from the potent negative NAO block-50/50 low dipole that is in place downstream stretching from Greenland down into the north atlantic. But pay close attention to the intensity of the west atlantic ridge (WAR) on the GFS as we begin to assess the other guidance.

 

 

The European guidance at the very same time frame during the predawn hours of Saturday, has the low in the same position as the GFS, but significantly more potent and still traveling to the northeast and into southeastern Canada, seemingly undeterred by the aforementioned north atlantic road block. This makes little sense, especially considering that the WAR on the EURO is even stronger than it is on the GFS, which in theory should cause an even greater shearing influence between it and the NAO, 50/50 dipole to its north. Additionally, over amplification is a known bias of this guidance that was just observed with respect to the current system in the medium range. The EURO likely has the correct idea with respect to the stronger WAR because the GEM has it modeled very similarly.

 

 

 

  It is not out of the ordinary that the GFS is a weak outlier with respect to the WAR because it has a bias of being too northern stream dominant. Additionally, the MJO is currently in phase 7.

 

 

Phase 7 of the MJO favors a strong WAR, which lends additional credence to the fact the GFS is in error in this respect.  

 

Thus the GEM is likely correct in modeling the system as succumbing to the confluent flow faster than other guidance, except for the fact that the GEM is is likely initializing the system too weak initially. This would lend credence to the GFS' middle ground position if it were not for the fact that it is likely under assessing the intensity of the WAR. However, the general track and thermal profile of the GEM can be accepted as the favored solution at this time given the fact that its under initialized intensity of the shortwave is essentially cancelled out by the under initialized strength of the WAR on the GFS depiction. 

That being said, this does not mean that the GEM is not currently over zealous with its QPF forecast, which must be accounted for given the shearing influence of the confluent flow that it encounters on approach to the region.

 

Favored Storm Evolution:

Snowfall break out across southwestern New England early Saturday evening.

 

 

And then quickly mix with and change to sleet, as a warm south westerly push at about the 700mb level in the mid layers of the atmosphere infiltrates the area.

 

 

The sleet progresses quickly to the MA/CT and MA/RI border by about midnight, as a mixture of sleet and rain continue over cape cod and the island and the primary low begins to transfer its energy to a secondary in the general vicinity of the Delmarva. 

 

But not before the decaying primary induces and easterly onshore flow near the coast.

It is during the predawn hours on Saturday, in the early stages of the system, where a coastal front is likely to establish itself in the vicinity of route 128 to the NW of Boston. 

 

This will separate a more marginal boundary layer due to an onshore flow, which will slow accumulations somewhat to the southeast, from a slightly colder air inland.

The penetration of sleet into the snow shield gradually slows and comes to halt near the Mass pike by about dawn on Saturday, as the low beings to transfer to the coast in the mid levels.

 

 

 

 

Note that while the low has redeveloped offshore at the 850mb level, it has not at the 700mb level and above, hence the transition to sleet and rain across the southern half of the region.

 

By midday on Saturday, the secondary has taken over and is tracking away offshore, which veers winds more out of the north and draws colder air back to the south.

 

 

This causes precipitation to change back over to snowfall before ending everywhere except for the cape and islands.

 

 

FIRST CALL:

 

 

Check back on Thursday for Final Call-

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Tuesday (2/28) Winter Storm Verification

Problematic Northern Stream Detrimental to Forecast

Here is the Eastern Mass Weather Final Call snowfall forecast map for yesterday's event.

 

Versus what actually took place.

Clearly the northern and northeastern third of the forecast did not materialize, as the forecast 2-4" and 3-6" ranges across northeastern Mass verified as 2" or less. However, the northern portion of the forecast area had the worst verification, where 4-8" was forecast for the northern Connecticut river valley and northern Worcester county, and 1-3" verified. The issue is that late northern stream injection of energy that was expected to revitalize the precipitation never materialized, which is where most of the snowfall in these areas was expected to occur, during the afternoon. The marginal low level temps across eastern areas did verify, which is why northeastern areas experienced slightly less snowfall (2" or less) than northern  locales well inland (1-3").  In summary, confluence was expected to prevent the heavy snows from reaching the northern and northeastern areas during the first portion of the storm, as evidenced by the soundings referenced in the Final Call. Thus round 1 on Monday night went as planned. But round 2 during the afternoon never materialized. The 3-6" and 2-4" forecast ranges across southeastern Mass and the upper cape verified because enough lift made it into these areas to negate the marginal lower levels to some extent. The rest of the forecast back to the west and southwest verified very well, including the 5-10" of max snowfall over the eastern slopes of the Berkshires, as a result of easterly flow resulting in an upslope component that enhanced snowfall slightly in this area.

 

FINAL GRADE C-

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Final Call for Friday Night-Saturday Winter Storm

No Major Changes

The forecast philosophy from First Call issued early on Tuesday AM remains largely unchanged, as anticipated trends in guidance given the stated rationale have largely materialized.

Synoptic Layout:

A vigorous piece of energy is currently ejecting out of the southwestern quadrant of the region and beginning its journey northeast.

 

 

 

 

The system is then forced to redevelop along the coast by the blocking pattern over the north atlantic.

 

 

 

 

However, given that there is there is currently a significant WAR in place due to the fact that the MJO is currently in phase 7, the primary should make it far enough north to cause major precipitation type issues across the southern half of the region.

 

 

Phase 7 of the MJO favors a strong WAR, which lends additional credence to the fact the GFS is in error in this respect.  

 

 

Favored Storm Evolution:

Snowfall break out across southwestern New England early Friday evening.

 

10pm Friday

 

 

And then quickly mix with and change to sleet by around midnight, as a warm south westerly push at about the 700mb level in the mid layers of the atmosphere infiltrates the area due to the fact that the parent mid level low will make it so far to the north into Ohio.

 

1AM Saturday

 

 

 

Snow will then likely mix with and perhaps change to sleet to at leas the Mass pike by dawn on Saturday.

 

7AM Saturday

 

 

With snow perhaps at least mixing with sleet at times later in the morning and towards mid day all the way to route 2 and perhaps the NH/VT borders, as the secondary low moves eastward and passes by to the south of Long Island. But accumulations will not be limited as greatly as they will to the south.

 

10AM Saturday:

 

The low will pass close enough by to induce and easterly onshore flow near the coast. Thus a coastal front is likely to establish itself in the general vicinity of the 128/495 belt to the NW of Boston Saturday morning.

 

 

 

This will separate a more marginal boundary layer due to an onshore flow, which will slow accumulations somewhat to the southeast, from slightly colder air inland where there is less marine influence.

 

The mid level warm intrusion should cease by afternoon, as the mid level low redevelops near Boston

 

 

This may cause precipitation to turn back to snow, however, additional accumulations should be limited since the mid level low does not appear as though it will redevelop fast enough or far enough to the south to impact the areas with the developing cold conveyor belt. This should remain to the north and east of the area.

 

 

 

FINAL CALL:

 

FIRST CALL: Issued Tuesday 2/28 at 545AM

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Friday Night-Saturday Winter Storm Very Well Forecast

Here is the Eastern Mass Weather Final Call forecast map for the winter storm that concluded earlier today.

 

 

Although the very marginal thermal profile around the region made this forecast particularly challenging, Eastern Mass Weather was up for this challenge in this instance.

Note the similarities between the above forecast and what actually took place.

 

 

Two relatively minor forecast imperfections being isolated amounts of up to a 1' in the Berkshires, where the upper bounds was only 10", and interior southeastern NH, where an extension of the 6-10" over the Monadnocks may have been more representative.

 

FINAL GRADE: A

 

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Major Storm Potential Looks Next Weekend

Protracted Ordeal Possible

Thus far in the early going, the month of March is setting a feverish pace to the regional weather, and early indications are that this may continue next weekend.

Cross Ensemble Consensus Supported by Teleconnector Convergence

All three major ensemble camps are in agreement that a potent piece of Pacific energy is gong to eject out of the western US over the course of the coming week, and is likely to become virtually pinned under a very congested north atlantic pattern next weekend.

 

EPS:

 

GEFS:

GEPS (Canadien): 

 

While it is an entirely fruitless endeavor to discuss specifics at this time, this is the type of regime that has bred very intense winter storms in the past, most notably March of 1956, which is a season that has been referenced frequently as a potential late season analog.  The potential period of interest is also coincides with a period of mass flux that is evident among both the Pacific:

 

And arctic domain spaces:

 

Which bolsters confidence that this time frame as it increased risk for a major event because this is the type of mass flux on a hemispheric scale that often triggers many of the regions most prolific winter storms.

 

Stay tuned for updates later this week if deemed appropriate.

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First Call for Major & Protracted Winter Storm Monday Night Into Wednesday

Power Outages & Coastal Flooding Concerns in Largest Event of Season

Dating back to last fall, Eastern Mass Weather utilized a combination of long range forecasting techniques, which included extensive ENSO analysis, identifying of both sensible weather and extra tropical Pacific analogs, to hone in on the first half of March as a window for a potentially memorable winter storm. With the passage of time, it had become apparent by latter February that the culmination of this window of opportunity would be during the second week of March. This due at last in part, to the lagged propagation of the major disruption of the stratospheric polar vortex, known as a Sudden Stratospheric Warming (SSW) that took place in during the middle portion of February. The timing of this evolution has resulted in a wonderful display of forecasting symmetry given that it coincides very closely with the year 1956, which was identified by Eastern Mass Weather as top ENSO and extratropical Pacific analog last fall. This is a season that also featured a potent bout of early season blocking that resulted in little snowfall across the area until the month of March. Here is how that month looked during the major winter storm that deposited 10-20"+ snowfall across much of the area on Mach 19, 1956.

 

As compared to the synoptic 500mb pattern for early next week.

 

 

While there are some differences, most notably the 500mb low is not diving as deeply to the south, this comparison is intended to convey similarities between the two respective winter seasons, than it is to imply synoptic comparisons to the storms, per se. Thus while the storm itself may not be a viable analog, the season is and it is no coincidence that a major storm appears imminent during this same timeframe 67 years later, which may result in a comparable snowfall.

 

Synoptic Situation:

The northern stream energy ultimately responsible for suppling a large portion of the energy for next week's storm came crashing onshore in the Pacific northwest on Friday.

 

 

 

The system will continue traveling eastward and will arrive in Minnesota on Sunday AM.

 

 

Then on Monday, the system will begin to dig in response to a building upstream ridge over the Rockies.

 

 

This ultimately causes it to begin interacting with a smaller parcel of energy moving up from the southern stream as the energy from the northern stream begins to infuse in to this system.

 

 

This process continues during the day on Tuesday.

 

 

Until the phase finally completes by Tuesday afternoon in the vicinity of Block Island, RI.

 

 

 And the new intense H5 low  drifts eastward, cuts off and virtually stalls overnight Tuesday, which prolongs the impact into midweek before it finally weakens and drifts away.

 

 

 

The precise interaction between these two parcels of energy will determine where exactly the heaviest snow falls, which is subject to change, but obviously higher terrain locales are favored for the heaviest amounts given the time of year and marginal antecedent airmass.

 

Expected Storm Evolution:

Precipitation will break out during the day on Monday in advance of the main system over southwestern New England. This will result from an inverted trough due to the conduit of energy feeding in from the northern stream to feed the developing storm. And will begin as primarily rain the lower elevations since it will be light in intensity, as heavy rates are needed to advect colder air from above downward in order to off set solar heating at this late juncture of the season. However, snow is likely from the onset over higher terrain.

 

1PM Monday:

 

 

Snowfall should remain largely relegated to the higher terrain into Monday evening, as the most significant precipitation remains focused around the inverted trough, while lighter more sporadic precipitation overspreads the remainder of the region.

 

7PM Monday:

 

 

Precipitation then overspreads the remainder of southern NewEngland Monday evening, beginning as rain near the coast and inside of rt 495, and snow further inland. Heaviest and steadiest precipitation continues to be focused on the inverted trough through the evening.

 

1AM Tuesday:

 

After midnight, the the focus for the precipitation begins to consolidate more on the coastal storm itself, as the nascent system begins to congeal and intensify. And the rain/ snow line begins to translate both lower in elevation and closer to the system.

 

4AM Tuesday:

 

 

By dawn on Tuesday, the more ferocious phase of the storm is underway, as it explosively deepens while approaching the cape and islands from the south. Heights crash and the transition to snowfall collapses to the lower elevations and to the coast. 

 

7AM Tuesday:

 

The strengthening solar irradiance begins losing the battle with snowfall by mid morning, as travel becomes exceedingly difficult to impossible. Winds increase dramatically and combine with very heavy snowfall to produce blizzard conditions at times.

 

10AM Tuesday:

 

The most ferocious portion of the storm occurs around midday with snowfall rates of 1-3" per hour and wind gusts out of the NE in excess of 50mph, which will pile water against the shore and batter the coast at time of high tide. The combination of heavy wet snow and strong winds will likely result in power outages, so please prepare.

 

1PM Tuesday:

 

A deep easterly fetch across the interior will cause down sloping in the Connecticut river valley, where significantly less snow will fall then other interior locations. Conversely, this will be an upslope flow that will enhance snowfall on the east slope of the Worcester hills and Berkshires.

 

The very heaviest bands of snowfall look to focus across central areas of the region, on the NW periphery of very intense 700mb frontogensis, with the highest amount over the hills in this band.

 

 

 

Heavy snow will continue into early Tuesday evening, with rain over the cape and islands.

 

4PM Tuesday:

Before finally a bating somewhat after dark on Tuesday.

 

7PM Tuesday:

However, since the system drifts away so slowly, light snowfall continues during the overnight Tuesday and into early Wednesday AM.

 

1AM Wednesday:

Lingering all day and finally ending Wednesday evening.

 

7PM Wednesday:

 

FIRST CALL:

Final Call to follow on Sunday-

 

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Final Call for Protracted Blizzard Monday Night Into Wednesday

Power Outages & Coastal Flooding Concerns in Largest Event of Season

Dating back to last fall, Eastern Mass Weather utilized a combination of long range forecasting techniques, which included extensive ENSO analysis, identifying of both sensible weather and extra tropical Pacific analogs, to hone in on the first half of March as a window for a potentially memorable winter storm. With the passage of time, it had become apparent by latter February that the culmination of this window of opportunity would be during the second week of March. This due at last in part, to the lagged propagation of the major disruption of the stratospheric polar vortex, known as a Sudden Stratospheric Warming (SSW) that took place in during the middle portion of February. The timing of this evolution has resulted in a wonderful display of forecasting symmetry given that it coincides very closely with the year 1956, which was identified by Eastern Mass Weather as top ENSO and extratropical Pacific analog last fall. This is a season that also featured a potent bout of early season blocking that resulted in little snowfall across the area until the month of March. Here is how that month looked during the major winter storm that deposited 10-20"+ snowfall across much of the area on Mach 19, 1956.

 

As compared to the synoptic 500mb pattern for early this week.

 

 

While there are some differences, most notably the 500mb low is not diving as deeply to the south, this comparison is intended to convey similarities between the two respective winter seasons, than it is to imply synoptic comparisons to the storms, per se. Thus while the storm itself may not be a viable analog, the season is and it is no coincidence that a major storm appears imminent during this same timeframe 67 years later, which may result in a comparable snowfall.

 

Synoptic Situation:

The system will continue traveling eastward after traversing the state of Minnesota during the day on Sunday.

 

 

Then on Monday, the system will begin to dig in response to a building upstream ridge over the Rockies.

 

 

This ultimately causes it to begin interacting with a smaller parcel of energy moving up from the southern stream as the energy from the northern stream begins to infuse in to this system.

 

 

Initially during the day on Tuesday, the two remain discrete entities.

 

 

 

However, heights begin falling throughout the day on Tuesday as the  northern stream energy begins phasing in during the afternoon and evening.

 

 

 

 

And is complete just after by around midnight late Tuesday night and early Wednesday AM, which i when the storm peaks in intensity.

 

 

 

 

 And the new intense H5 low slowly drifts eastward on Wednesday, with the last of the significant snowfall exiting cape cod around midday.

 

 

 

While the precise interaction between these two parcels of energy will determine where exactly the heaviest snow falls, the higher terrain locales are clearly favored for the greatest amounts due to increasing sun angle coupled with a marginal airmass.

Expected Storm Evolution:

Precipitation will break out during the day on Monday in advance of the main system over southwestern New England. This will result from an inverted trough due to the conduit of energy feeding in from the northern stream to feed the developing storm. And will begin as primarily rain the lower elevations and near the coast. This is due to the fact that it will be light in intensity, as heavy rates are needed to advect colder air from above downward in order to off set solar heating at this late juncture of the season. However, snow is likely from the onset over higher terrain.

 

7PM Monday:

 

 

 

Snowfall should remain largely relegated to the higher terrain into Monday evening, as the most significant precipitation remains focused around the inverted trough, while lighter more sporadic precipitation overspreads the remainder of the region.

 

 

1AM Tuesday:

 

 

Precipitation then overspreads the remainder of southern NewEngland Monday evening, beginning as rain near the coast and inside of rt 495, and snow further inland. Heaviest and steadiest precipitation continues to be focused on the inverted trough through the evening. Precipitation remains rain for much of the area during phase 1 of the storm, on Tuesday morning, due to warmer air being drawn in on a south southeasterly flow around an initial wave of weak low pressure moving into Connecticut.

 

7AM Tuesday:

 

Warmest Point at 7am Tuesday

 

North of this south southeasterly flow, a deep easterly fetch across the interior will cause down sloping in the Connecticut river valley, where significantly less snow will fall then other interior locations. Conversely, this will be an upslope flow that will enhance snowfall on the east slope of the Worcester hills and Berkshires.

 

 

Ultimately this low, a reflection of the incoming northern stream energy, will begin to die out as the phase begins and energy translates eastward to meet the southern stream disturbance, which will allow heights to crash and temps to begin to drop during the day on Tuesday.

 

 

Precipitation quickly changes to snowfall right down to cape cod by Tuesday evening, as a period of near blizzard conditions commences later in the evening, when snow grows steadier and heavier as the system matures offshore.

 

7PM Tuesday:

 

 

Phase two of the storm begins Tuesday evening, as the strengthening solar irradiance begins losing the battle with snowfall by the evening commute. Travel becomes exceedingly difficult to impossible. Winds increase dramatically and combine with very heavy snowfall to produce blizzard conditions at times.  The combination of heavy wet snow and strong winds will likely result in power outages, so please prepare accordingly. This is obviously the period when eastern areas pick up the majority of accumulation while the phased system reaches peak intensity just offshore.

 

1AM Wednesday:

 

 

The most ferocious portion of the storm should last into the wee hours of the morning, with snowfall rates of 1-3" per hour and wind gusts out of the NW in excess of 50mph as the system begins to pull away. This could cause coastal flooding issues on the upper cape.

 

 

Snow should begin tapering off by the Wednesday morning commute, but the damage will have been done and it should be a slow one.

 

7AM Wednesday:

The last of the significant snowfall should exit the cape around midday, as the system slowly drifts away and winds taper down.

 

1PM Wednesday:

FINAL CALL:

 

 

 

FIRST CALL: Issued 3/11 @ 4AM

[40/70 Benchmark]

Decent Forecast for Very Difficult & Protracted Major Winter Storm

Here is the Eastern Mass Weather Final Call forecast map for the major, long duration winter storm that concluded early yesterday morning.

 

 

Here is what actually verified in terms of snowfall across the southern New England Region.

 

 

While the forecast did in exemplary job identifying the areas where 30" or more of snow would fall, the gradient was too broad on the southern and eastern portions of the heavy snowfall area, over south central and eastern Mass. Obviously this is not ideal because this is the most densely populated area of the region.

There are two reasons for this forecasting error:

1) The forecast failed to convey the extent to which the warm protrusion at roughly the 925mb level, caused by the dying primary surface low over Connecticut, would limit snowfall at lower elevations over southern Worcester county. 

 

 

 

 

This resulted in an obscene snowfall gradient over the city of Worcester to the degree that lower elevations on the southern side of the city say just a few inches, while just a 3-4 miles to the north and a few hundred feet higher up accumulated over 2 feet of snow. Where as the gradient of forecast ranges employed in this area was from 6-12" to 15-25".

This at least partially explained by the second reason for the forecasting error.

 

2) The reason that snowfall was significant less than anticipated across the eastern portions of the area is not due to thermal fields, as this was well predicted. In fact, precipitation actually transitioned to snowfall slightly earlier than forecast on Tuesday AM. The reason that the forecast called for several more inches of snow than actually fell across the densely populated eastern areas, which includes the Boston area, is because there simply wasn't as much precipitation pivoting around the backside of the circulation of the developing coastal storm as forecast just one day prior, which is when the final call was made.

 

Here is the QPF forecast from the 00z Monday European guidance for the early afternoon on Tuesday into Tuesday evening , at which point precipitation had already transitioned to snowfall across most of eastern Mass.

 

00z Monday European 6hr QPF valid 00z Wednesday

 

Note that it implies up to an inch of additional precipitation, which would have resulted in at least several inches of snowfall.

 

However, here is the forecast from Tuesday afternoon from that very same model.

Now you see a great deal of QPF...

 

12z Tuesday European 6hr QPF valid 00z Wednesday

Now you don't.

 

All of a sudden over the span of the 24 hours after the forecast was issued, .3" of QPF is expected to fall as snow on Tuesday afternoon over eastern areas, as opposed to an inch. This is essentially why the southern half of the 12-20" forecast range verified as 5-10", and why the several inches of snowfall forecast for the Boston area and southeastern Mass verified as more like 1-3"

Thus the contingent of meteorologists and hobbyists alike that are claiming validation for the belief that it wasn't cold enough for significant snowfall in these regions are either incorrect and/or disingenuous. The fact of that matter is that it was marginally cold enough, but the precipitation was more banded and less organized because the primary mid level system was slower to transfer energy to the coast than forecast just one day earlier.

FINAL GRADE: B-

[512high]

6 hours ago, 40/70 Benchmark said:

Decent Forecast for Very Difficult & Protracted Major Winter Storm

Here is the Eastern Mass Weather Final Call forecast map for the major, long duration winter storm that concluded early yesterday morning.

 

 

Here is what actually verified in terms of snowfall across the southern New England Region.

 

 

While the forecast did in exemplary job identifying the areas where 30" or more of snow would fall, the gradient was too broad on the southern and eastern portions of the heavy snowfall area, over south central and eastern Mass. Obviously this is not ideal because this is the most densely populated area of the region.

There are two reasons for this forecasting error:

1) The forecast failed to convey the extent to which the warm protrusion at roughly the 925mb level, caused by the dying primary surface low over Connecticut, would limit snowfall at lower elevations over southern Worcester county. 

 

 

 

 

This resulted in an obscene snowfall gradient over the city of Worcester to the degree that lower elevations on the southern side of the city say just a few inches, while just a 3-4 miles to the north and a few hundred feet higher up accumulated over 2 feet of snow. Where as the gradient of forecast ranges employed in this area was from 6-12" to 15-25".

This at least partially explained by the second reason for the forecasting error.

 

2) The reason that snowfall was significant less than anticipated across the eastern portions of the area is not due to thermal fields, as this was well predicted. In fact, precipitation actually transitioned to snowfall slightly earlier than forecast on Tuesday AM. The reason that the forecast called for several more inches of snow than actually fell across the densely populated eastern areas, which includes the Boston area, is because there simply wasn't as much precipitation pivoting around the backside of the circulation of the developing coastal storm as forecast just one day prior, which is when the final call was made.

 

Here is the QPF forecast from the 00z Monday European guidance for the early afternoon on Tuesday into Tuesday evening , at which point precipitation had already transitioned to snowfall across most of eastern Mass.

 

00z Monday European 6hr QPF valid 00z Wednesday

 

Note that it implies up to an inch of additional precipitation, which would have resulted in at least several inches of snowfall.

 

However, here is the forecast from Tuesday afternoon from that very same model.

Now you see a great deal of QPF...

 

12z Tuesday European 6hr QPF valid 00z Wednesday

Now you don't.

 

All of a sudden over the span of the 24 hours after the forecast was issued, .3" of QPF is expected to fall as snow on Tuesday afternoon over eastern areas, as opposed to an inch. This is essentially why the southern half of the 12-20" forecast range verified as 5-10", and why the several inches of snowfall forecast for the Boston area and southeastern Mass verified as more like 1-3"

Thus the contingent of meteorologists and hobbyists alike that are claiming validation for the belief that it wasn't cold enough for significant snowfall in these regions are either incorrect and/or disingenuous. The fact of that matter is that it was marginally cold enough, but the precipitation was more banded and less organized because the primary mid level system was slower to transfer energy to the coast than forecast just one day earlier.

FINAL GRADE: B-

Ray ,

Thanks every year for your insights, I and I'm sure others here and elsewhere look forward to next season, maybe next year will be better with a "Nino" not too much just the right amount to give hopefully SNE a great winter.

 

Philip