Winter '23-'24 Will Be A Lesson In Relativity

[40/70 Benchmark]

3 hours ago, Typhoon Tip said:

Dude... this looks like a crude attempt at a STJ

https://www.tropicaltidbits.com/sat/satlooper.php?region=atlpac-wide&product=truecolor

..time sensitive

I don't particularly like recent trends with the bulk ensemble means, from either the EPS of GEFs through the 20th.  Rumor has it the deep field astronomy has the cosmos expanding into cold fantasies - maybe, no opinion for now.

Well, probably because through 12/20 sucks.

[40/70 Benchmark]

Mild December Continues with Changes Slow to Evolve

Maritime Forcing Remains Prevalent

The polar vortex has began to recover as expected following the brief period of blocking that occurred near the onset of the month of December.

 

This intensification of the vortex has occurred concurrent with the progression of the MJO into the Maritime region, which was described in last month's Winter Outlook as being the primary reason why December 2023 would be significantly milder and less wintery than analog seasons such as 2009-2010.

"Some periods of a stronger PV are likely, especially early on, as implied earlier. This placement is also quite similar to the mean seasonal forcing during the QBO/solar el Nino analog season of 2009-2010, albeit even slightly further to the west as to include more maritime phase 6 involvement":

 

"Which is one of the reasons why the coming season is unlikely to rival that one in terms of consistent cold and record magnitude of blocking/mid Atlantic snows". 

 

 

 

 

Note that currently forcing is biased towards the western edge of the above composite, which is consistent with Maritime phase 6.

 

The progression of the MJO through the phases 6-8 for the balance of December will also be accompanied by a Pacific jet extension, as annotated by highly skilled meteorologist John Homenuk.

 

 

 

Powerful Jet Extension Marked by +EPO

This feature is due to the development of a powerful Gulf of Alaska low that will take shape between now and the holiday period.

 

 

 This regime is redolent of the strong and/or east-based canonical El Niño composite that Eastern Mass Weather asserted would be a prominent feature during the month of December.

 

 

This confluence of factors will not only mean that the next powerful coastal system scheduled for early next week will also be rain.

 

But that that the balance of the 2023 will finish at least as warm as anticipated (+1 to +3F) and potentially somewhat warmer.

 

However, be that as it may, the notion that the new year will indeed herald in a new weather regime remains unchanged.

 

End of December to Feature Changes & Paradoxical Early January Developments

The final week of 2023 should be a period of great flux, both at the surface.

 

 

But most especially in the stratosphere, as warming should begin to accelerate during the last week of December and culminate in a SSW during the first week of the new year.

 

 

 

 

Tropical forcing should also align closer to the dateline, which is more congruent with the anticipated mean seasonal position.

 

 

And similar to some of the more notable analog seasons.

 

 

 

 

This will be accompanied by the MJO methodically navigating its way into a relatively meager phase 1 and 2 expression.

 

 

The late December and early to mid January period promises to be somewhat paradoxical in the sense that the colder pattern triggered by the navigation of tropical forcing back to the general vicinity of the dateline will be countermanded by the energy flux from the troposphere into the stratosphere. This will likely act to truncate the somewhat colder period and lead to yet another mild period during the middle and perhaps latter portion of January, much to the chagrin of frustrated eastern US winter weather aficionados. However, this is a short term trade off for what promises to be a longer term late winter-time bonanza, so to speak. This evolution is endorsed by Dr. Judah Cohen.

"It is of my opinion, much of the winter will likely hinge on the nature of this SSW that is predicted to begin the last week of December. I think the models were slow to appreciate the magnitude of the energy transfer from the troposphere to the stratosphere. Where the energy leaves or diverges it creates cold, low pressure and the westerly winds increase or in this case in the troposphere. Where the energy enters or conerges it creates warm, high pressure and the westerly winds decrease or in this case in the stratosphere. That is why I believe that the weather models both showed a more robust weakening of the PV simultaneously predicting more low pressure and less high latitude blocking in the troposphere and milder temperatures across the continents".

More to follow prior to the New Year, or should any winter threats emerge for SNE in the interim.

[40/70 Benchmark]

Quiet & Mild Christmas Will Transition to Progressively More Seasonable Holiday Stretch

Significant Snowfall Unlikely Until 2024

Using history as a guide, Eastern Mass Weather explained in the Winter Outlook why the convective forcing pattern in association with el Nino that had become established throughout the fall was unlikely to change during the winter. Thus far in the early going this has proven accurate.

 

 

As forcing has remained anchored in the vicinity of region 4 on the western flank of El Niño, which  coincides approximately with MJO phase 7.

 

 

This represented a large portion of the rationale for expecting a fairly mild first month of meteorological winter.

Note the resemblance between the composite for MJO phase 7 during an El Niño:

 

 

The December composite of robust El Niño events per meteorologist Eric Webb:

And the current pattern across the North America:

 

 

 

However, the changes that were expected to evolve during the holiday period and into the new year are underway and are beginning to be signaled more emphatically among guidance.

 

New Year: New Weather Pattern

There is growing support for the highly anomalous ridge that has been residing in the center of the continent as a by product of a ferocious Pacific jet to retrograde to the northwest.

 

 

And eventually reach a position in northwestern Canada that will allow for the delivery cold colder air as the Pacific jet retracts. 

 

 

This is consistent with the progression of an El Niño season in which convective forcing is focused at the western flank of the ENSO regions as 2003 gives way to 2024.

 

While colder air is unlikely to become entrenched enough to afford much opportunity for a significant winter storm for the middle portion of next week across the forecast area, some significant snow is possible across the higher terrain and especially northern New England.

 

 

 

 

Then all eyes focus on the anticipated warming of the polar stratosphere and likely SSW as the ball drops, which promises to couple with the aforementioned changes to ensure an active second half of winter.

 

 

 

[mreaves]

How does 1979/80 do as an analog?

[40/70 Benchmark]

1 hour ago, mreaves said:

How does 1979/80 do as an analog?

I think I incorporated it as a February analog.

[mreaves]

15 minutes ago, 40/70 Benchmark said:

I think I incorporated it as a February analog.

I was thinking about it today as I remember it being awful for snow up here. I think the first significant snow was in February. 

[40/70 Benchmark]

Very Mild December Prompts Change to Forecast Methodology; January Looks to be a Month in Flux

Stratospheric Warming Likely Early in 2024

December 2023 Review:

Using history as a guide, Eastern Mass Weather explained in the Winter Outlook why the convective forcing pattern in association with el Nino that had become established throughout the fall was unlikely to change during the winter. Thus far in the throughout the month of December this has proven accurate.

 

 

As forcing has remained anchored in the vicinity of region 4 on the western flank of El Niño, which  coincides approximately with MJO phase 7.

 

 

This represented a large portion of the rationale for expecting a fairly mild first month of meteorological winter.

Note the resemblance between the composite for MJO phase 7 during an El Niño:

 

 

The December composite of robust El Niño events per meteorologist Eric Webb:

And the pattern across the North America throughout the Holiday period:

 

 

However, there are two points that have become clear throughout the month of December. First of all, it has become apparent that the DM seasonal forecast composite inadequately conveys the anticipated monthly progression over the course of the winter season. This is due to the fact that during any given year, there may be several analogs that may progress differently, despite ending up fairly decent matches in the DM seasonal mean. It was very apparent this December.

Here is the 500mb verification and associated temperature anomaly map for the month thus far through 12/26:

 

Versus the DM mean composite for the month of December:

 

 

Note how the December forecast composite derived from the DM mean seasonal composite fails to capture the deep vortex in the vicinity of Alaska, which drove the active Pacific jet that eradicated the cold air supply from the North American continent.  However, the December analog composite does not miss this feature and also more accurately conveys the anticipated +1 to +3 forecast temp departures across the forecast area for the month of December. 

 

 

 

The second point is that the December analog derived forecast was still not warm enough, as many regional departures will finish several degrees above average. However, be that as it may, it is clear that the monthly analog derived composite provides a more precise representation than the DM mean seasonal progression and will thus be used moving forward. 

Here is the precipitation forecast, which underestimate regional precipitation as another consequence of the intense Pacific jet:

 

Versus reality:

Overall the month was milder than anticipated in large part due to just how overwhelmingly prominent that Pacific jet remained, as southern New England saw little to no snowfall regionwide. But the rest of the teleconnections largely behaved as anticipated.

 

"While the month should finish slightly mild in the mean, it will be fairly active and should not be completely void of winter weather for the NE coastal plane, as there should be transient spasmodic PNA flexes. In fact, snowfall may very well be above average for the month across the deep interior and northern New England, where ski resorts should benefit from a blend of coastal storms and southwest flow events".

The AO averaged essentially neutral with a slight negative bias:

 

The NAO neutral with a slight positive bias:

 

 

And the PNA slightly positive, albeit variable:

 

 

 

The predicted descent in the PNA may play a crucial role in modulating the rate of any pattern evolution as we head into the New Year.

 

January Forecast Remains Consistent with Some Warmer Risks

Early January still appears to grow more seasonable from the very mild December regime, as the Alaskan vortex finally begins to dislodge, however, the forecast decline of the PNA is reflective of the fact that said lower heights look to translate down the west coast.

 

 

This evolution is consistent with the forecast position of tropical convection entering MJO phase 3.

 

 

And if anything the correction vector is pointed warmer per Paul Roundy's extra tropical regression tool.

 

Tropical convection is then forecast to reach into Maritime phase 4 by mid month.

 

Ascent Increases Over Maritime Continent of Indonesia & Descent Develops Over Western Pacific by Mid January

 

 

This is congruent with the anticipated mid month warm up described in the Eastern Mass Weather winter outlook.

 

 

"This should largely be a tale of two months, as the warmer than average first half should give way to a colder second half that will be accompanied by the first of two historic seasonal snowfall potentials. The first half of the month should focus appreciable snowfall across the interior of southern New England, however, the coastal plane should join with a vengeance".

And whether or not the impending early January stratospheric warming ultimately meets the technical definition of a SSW and triggers a reversal of the higher level winds from westerly to easterly per forecast remains up for debate. But Judah Cohen currently favors a SSW and subsequent split of the polar vortex.

"The PNA should remain variable, which will continue to fuel an active pattern as the PV grows increasingly more disturbed in the wake of a SSW during the window from about Christmas through January 8". 

Regardless, what is clear is that the polar vortex should ultimately remain increasingly disturbed as the month of January progresses.

 

Thus the energy from said stratospheric warming should have completed its downward propagation into the troposphere around the same time that the MJO exits the Maritime continent by around approximately January 20th and beyond. It is at this point that the watch begins in earnest, as per the Eastern Mass Weather winter outlook progression.

"A NESIS caliber storm is likely during the window between approximately January 22 and February 5, however, there is a possibility that it will be focused to the south of New England".

This conceptualization is reinforced by research conducted by meteorologist Eric Webb.

 

 

Until that time keep a close vigil on what promises to be a very volatile month replete with large scale flux and constant pattern evolution.

Here are the forecast composites for review.

January forecast H5:

Versus current guidance:

 

 

 

January Forecast Temperature Anomalies:

 

Versus Current guidance:

 

 

January Forecast Precipitation Anomalies:

 

 

 

[40/70 Benchmark]

First Significant Winter Storm Threat Next Weekend

Significant Differences Amongst Guidance

Winter 2023-2024 has undoubtedly featured a slightly slower start than anticipated, as the end of what was a very mild month of December approaches on the eve of January 2024. And it looks as though winter may finally be preparing to make a grande entrance just one week into the new calendar year.

Guidance is in early strong agreement that a lead system on Thursday will remain to the south of the region.

 

 

However, the plot then thickens, as there is understandably much less of a consensus with respect to the follow up system next Sunday.

Two Main camps

The European ensemble suite:

 

 

And the Canadien ensemble are both slightly faster to deepen the Western US trough, which results in an increase in Southeast heights down stream. 

 

 

This allows the wave to exit the coast at a higher latitude, which increases the threat of a winter storm for the southern New England forecast area. However, the European guidance depicts a slightly more amplified shortwave passing to the south of Long Island upon exiting the coast, which would result a major storm. Whereas the Canadien suite, while far enough north to impact the area, would suggest potentially more of a moderate winter storm. But the important note at this stage as that both pieces of guidance agree on a storm for the area next weekend, which in contrast to the GEFS, which suggests a near miss.

The GFS ensemble suite is slower to amplify the western trough and thus has a delayed response with respect to increasing downstream heights over the southeastern US.

 

 

This does not allow the system to gain as much latitude and results in a snowstorm for the mid Atlantic, but not much in the way of snowfall for most of southern New England. While it may ostensibly appear that the GFS suite is the outlier here, there is reason for pause before endorsing the snowier EURO/Canadien compromise.

 

Tropical Nod to the GFS

There is a strong consensus that the MJO will be entering phase 3 late this coming week and into next weekend.

 

 

And progression of the MJO into phase 3 offers support for a slower amplification of the west coast trough more in line with the GFS suite. 

 

 

 

Although the ECMWF rapidly weakens the MJO wave in phase 3, it does still spend 3+ days in this area in the lead up to the period of interest on the 7th. 

The prudent course of action at this stage is to stay tuned throughout the week and plan on at least some snowfall next Sunday, especially to the south of the Mass pike and through Connecticutt and Rhode Island.

 

[40/70 Benchmark]

First Call for Snowy Sunday

 Season's First Significant Snowfall Likely

Synoptic Overview:

The latest in a long line of El Niño fueled, moisture laden southern stream systems will eject northeast out of the southwestern US over the weekend.

 

 

However, one key difference will be the arrival of a cold air mass in advance of this weekend's storm, as Thursday's seaward system drives in a colder airmass in its wake late in the week. 

 

 

At the same time, heights over the southeastern US will be rising in response to the deepening system over the southwestern US. This will work in conjunction with the pressing of Canadian high pressure to the north to compress the flow around the storm system as it ejects east northeast thought the region on Sunday. The result of this is:

1) Unlike the previous chain of storm systems throughout December, this storm will have cold air to work with and will thus be the region's first significant winter storm.

2) The storm should be weaker than some of the previous systems this fall, some of which having produced violent winds. The main impact should be a region wide moderate to perhaps localized heavy snowfall on Sunday, as winds, albeit it breezy near the coast, should not be a major factor.

 

Anticipated Storm Evolution:

    Snowfall should breakout by midnight over the western half of southern New England on Saturday night.

 

And then rapidly overspread the balance of the area over the course of the pre-dawn hours on Sunday, perhaps as a mixture of rain and snow on the south coast before transitioning over to snowfall.

 

The outer cape and islands should have a more significant period of rainfall to cutdown on accumulations Sunday morning. Some locally heavier accumulations may occur in band just to the north of the closing 700mb low.

 

The outer cape and islands should transition back to snowfall Sunday afternoon as the low begins to pull away.

 

Snowfall should gradually taper off from west to east during the latter portion of the afternoon.

 

 

And exiting the outer cape during the evening. hours.

 

 

FIRST CALL:

Final call will be issued on Saturday.

[Greg]

Great analysis Ray. Really get into it. Always loved that stuff.

[512high]

Like Greg said, Thanks for taking the time to do this, hope to have many more of your outlooks all winter!

[40/70 Benchmark]

Messy Mid Week Possible Following Season's First Significant Winter Storm This Weekend

Tropics & Polar Domain in Conflict

The first weekend of the year promises to be a crucial point of inflection for the the 2023-2024 winter season. Not only will this weekend's impending winter storm have a significant impact on Sunday travel plans, but concurrent with this will be developments in the polar stratosphere that will have important implications on the balance of the winter season. Incidentally, there is now strong agreement amongst guidance that the long awaited split of the polar vortex that has been eagerly anticipated dating back to this past fall (between Christmas and January 8th) will be taking place concurrent with our Sunday snowfall.

 

 

Despite the fact that a technical SSW may not occur.

 

 

This is reflected by what is forecasted to be a very disturbed polar domain for the foreseeable future.

 

 

However, the deep trough that is forecasted to amplify over the Western CONUS this weekend is also forecasted to persist well into the month of January.

 

This is due to the fact that the MJO is forecasted to amplify in phase 4 by mid month.

 

This will only serve to bolster the west coast trough per both the MJO phase 4 January composite:

 

 

And MJO regression guidance.

 

The synoptic evolution that will follow includes the polar vortex lobe in the vicinity of James Bay initially descending into the western US.

 

 

 A sequence that will reenforce the deep western trough at the same time that a major storm system is ejecting out of the Southwest next week.

 

 

While primarily rainfall is expected across the region, stay tuned for potential updates over the course of the next week for updates regarding how this system will interact with the developing NAO block.

 

INITIAL THREAT ASSESSMENT:

[40/70 Benchmark]

Final Call for Moderate to High Impact Sunday Snowfall 

Upwards of One Foot Possible Well North & West of Boston

Synoptic Overview:

The latest in a long line of El Niño fueled, moisture laden southern stream systems will eject northeast out of the southwestern US this weekend.

 

 

However, unlike the previous systems, cold air is being introduced into the equation on the heels of Thursday's seaward system and in advance of this weekend's storm.

 

 

At the same time, heights over the southeastern US will be rising in response to the deepening system over the southwestern US. This will work in conjunction with the pressing of Canadian high pressure behind the departing 50/50 low to compress the flow ahead of the first disturbance that approaches the region late Saturday night and early Sunday.

 

While the confluence to the north will compress and attenuate the lead wave, it now appears as though a follow up wave will reinvogirate the system during the day on Sunday to some degree, as it is departing the region. Just how quickly this system closes in the mid level is crucial to whether there is simply snow showers during Sunday afternoon, or heavy banding of accumulating snowfall. 

 

 

While guidance has trended more aggressively with the rate of intensification upon exit, the ultimate evolution is often slower and the system more progressive than guidance suggests, which can lead forecasters astray by overestimating snowfall to a degree. This situation it has high risk for such a development given the fact that there is no upstream ridging over the western CONUS to slow the flow down.

Anticipated Storm Evolution:

Snowfall should break out across western Connecticut early Saturday evening. Meanwhile, back in eastern sections, coastal frontogenesis will be triggered by onshore east-northeast (east of the front) to northeasterly winds (west of the front).

 

Then snow mixes with and changes to rainfall along the south coast of Connecticut, Rhode Island, and southeast Mass by midnight, as precipitations begins as rain over the cape and islands.

 

This is the warmest point of the storm as the marine influence propels the coastal front to its furthest north and west point, just beyond the I-495 belt in Mass and down through eastern Connecticut and along the south coast.

 

Snowfall is enhanced via added lift just to the northwest of the coastal front, over southeastern New Hampshire, NW Middlesex County and the eastern slopes of the Worcester hills. The latter of which will also see augmented snowfall via upslope from a deep easterly fetch in the mid levels of the atmosphere. The risk for power outages will be greatest where a significant amount of heavy, wet snow falls to the east of the coastal front in the initial stages of the storm, along the immediate north shore, Boston area and down I 95 over interior southeastern Mass.

 

While precipitation will be heaviest along the east slopes of the higher terrain, this deep easterly fetch will coincide will enhance precipitation in general across the region during the predawn hours of Sunday morning.

 

 

There may be somewhat of a lull later on Sunday morning, which represents a crucial point of inflection for this storm system and its degree of regional impact.

 

The evolution of the storm system in the mid levels of the atmosphere is what will determine whether or not this system has a moderate or major impact on the area. And it should become clear how quickly the energy infusion into the lead system from the trailing wave will coalesce into an intensifying coastal system by midday Sunday.

The trend during the day on Friday has been for the system to begin to close off in the mid levels of the atmosphere by early afternoon on Sunday.

 

 

Which will begin to increase snowfall just to the northwest of the fledgling 700mb low over the same areas that experienced enhancement during the first half of the event from coastal frontogenesis and upslope. 

 

These heavier bands will begin to crash towards the coast as the surface system pulls the coastal front back towards the coast and the mid level system continues to mature.

 

 

Briefly heavy snow and " 'flash freeze conditions are possible near the coast at this point during Sunday afternoon.

 

The system should begin to pull away by Sunday evening.

 

Taking the snowfall with it, but not before light accumulations on the cape and islands, as any rainfall transitions to snow prior to ending prior to midnight over the outer cape.

 

 

 

FINAL CALL:

 

First Call issued Wednesday 1/3 @ 11AM.

 

 

[40/70 Benchmark]

Sunday Snow Forecast Fairly Well

Amounts Slightly Heavier Inland and Lower Than Forecast Immediate Coast

Here are the snowfall amounts from yesterday's storm versus the Eastern Mass Weather Final Call.

 

 

 

The forecast overall was a high quality effort, however, there were two glaring issues.

1) The 8-14" area of maximum forecast snowfall, while generally accurate, would have been better served to reflect 12-18" and be positioned ever so slightly to the south of where it was in the forecast. There also should have been a secondary area over northwestern Connecticut.

2) The more glaring error was the forecast for 5-10" along the immediate coast in the densely populated Boston area, whereas the lower levels remained warm enough to limit accumulations to as low as 3.1" at Boston's Logan International Airport. However, amounts of over 6" were observed just away from the ocean (6.5" Brookline, MA) in the Boston area, as well as over interior southeastern Mass (6.25" in Taunton, MA). Suffice to say, the gradient along the east coast was not quite sharp enough to reflect the thermal changes from the marine influence.

 

Final Grade: B+

[512high]

2 hours ago, 40/70 Benchmark said:

Sunday Snow Forecast Fairly Well

Amounts Slightly Heavier Inland and Lower Than Forecast Immediate Coast

Here are the snowfall amounts from yesterday's storm versus the Eastern Mass Weather Final Call.

 

 

 

The forecast overall was a high quality effort, however, there were two glaring issues.

1) The 8-14" area of maximum forecast snowfall, while generally accurate, would have been better served to reflect 12-18" and be positioned ever so slightly to the south of where it was in the forecast. There also should have been a secondary area over northwestern Connecticut.

2) The more glaring error was the forecast for 5-10" along the immediate coast in the densely populated Boston area, whereas the lower levels remained warm enough to limit accumulations to as low as 3.1" at Boston's Logan International Airport. However, amounts of over 6" were observed just away from the ocean (6.5" Brookline, MA) in the Boston area, as well as over interior southeastern Mass (6.25" in Taunton, MA). Suffice to say, the gradient along the east coast was not quite sharp enough to reflect the thermal changes from the marine influence.

 

Final Grade: B+

Great job, can't remember a 16" event in quite awhile ...good stuff!

[40/70 Benchmark]

Active January Pattern to Continue

Degree of Winter Weather Impact to be Determined.

The next in a line of significant storm systems to impact southern New England this month is on tap for Wednesday, however, it looks to be primarily a rain and wind threat with the system tracking through the great lakes.

 

The primary considerations for this system will be high wind and heavy rains, which will combine with snow melt from the this past weekend's storm to potentially cause some flooding in poor drainage areas. 

Significant snowfall is possible for northern ski areas given the late transfer to the coast as the system approaches the developing NAO block.

 

 

The block will continue to become stronger and more entrenched further to the west throughout the duration of the week, such that it will be better positioned to induce a faster coastal transfer with respect to the approaching storm system next weekend.

Better Chance for Some Wintry Impact Southern New England Next Weekend

Given the modeled strength and positioning of the developing block, there should be some trends toward faster redevelopment of the next system over the weekend.

 

But whether or not it will be enough to result in a significant winter storm for southern New England remains to be seen.

[40/70 Benchmark]

Mild, Wind Swept Weekend Rains Represent Crucial Point of Inflection for Winter 2023-2024

Some Snow Possible Tuesday & Larger Threat Looms in Extended Range

Fast on the heels of last night's heavy rains, the second in a sequence of dual heavy rain events looks to extinguish the balance of any existing snowpack across the northern portion of the region on Saturday.

In a virtual reenactment of Tuesday evening, yet another short wave breaks off from the consistent energy feed out west and amplifies abruptly in the midwest, which results in yet another track through the Great Lakes.

 

 

It is clear that any resistance to such a track form the developing NAO block will be insufficient to lead to a more wintry outcome as a result of the mild airmass left in the wake of last night's storm system. This may understandably lead the general public to the ill-fated conclusion that winter 2023-2024 will be relatively uneventful in terms of winter weather, much like last season, given the dearth of snowfall near the coast by the midpoint of the season. However, ironically enough, it is this mild weekend rainstorm that will play an instrument role in the inflection point at which this season diverges from the rather meek winter of 2022-2023.

 

Seeds of Changes to be Planted this Weekend

It was opined last fall that the first half of January would be relatively mild with snowfall focused over the interior. Thus far that has proven accurate given the mean temperature anomaly through the first week to ten days:

 

 

 And the first significant snowfall of the season last weekend.

 

 

 

 

 

However, while the high latitude block that is currently developing is not going to keep this weekend's system from passing inland, it will act to ensure an avenue for the delivery of arctic air in the wake of the storm. And that is precisely what this storm will do, as it meanders about Canada and retrogrades underneath the Greenland block as a functional polar vortex lobe. 

 

And insodoing it will also force the potential system slated to arrive approximately late on Tuesday further to the south, ensuring primarily wintry precipitation and greatly increasing the risk for significant snowfall across the region and closer to the coast.

 

 

 

And thereafter the plot thickens beyond mid month,  as per the progression conveyed in the Eastern Mass Weather Winter Outlook that was issued this past fall.

"This should largely be a tale of two months, as the warmer than average first half should give way to a colder second half that will be accompanied by the first of two historic seasonal snowfall potentials. The first half of the month should focus appreciable snowfall across the interior of southern New England, however, the coastal plane should join with a vengeance. A NESIS caliber storm is likely during the window between approximately January 22 and February 5".

Indeed, high end potential looms as the NAO block begins to relax. And the polar vortex lobe translates east before lifting north into a "50/50 low" position, which will act to hold the cold air that it helped to deliver in the wake of this weekend's system.

 

 

This is represents a rather robust signal, which is rooted in teleconnector convergence via mass flux throughout the hemisphere in both the Atlantic/Arctic:

 

 

And the Pacific/Arctic:

 

 

 

 

 In what is a classic Archambault signal for a major east coast precipitation event.

Keep all eyes on the blog for developments through the weekend and into next week as what ostensibly appears to be mild rain storm plays a crucial role in altering what has been a benign temperament of winter 2024. Indeed, changes appear to be afoot. 

 

[40/70 Benchmark]

First Call for Light Snows Tuesday; Larger Potential Looms Next Weekend

Manageable Snows Overnight Tuesday

Synoptic Overview 

This weekend's rain storm is becoming stuck underneath the negative NAO block, which will allow it to act as a polar vortex lobe. A modest piece of vorticity (energy) will rotate around the southern periphery of this system and trigger a round of light to potentially moderate snowfall overnight Tuesday.

 

Anticipated Storm Evolution:

Light snow or flurries should break out over southern portions of the region during the afternoon into the early evening.

 

 

 

And become occasionally moderate overnight Tuesday night across the southeastern half of Southern New England.

 

 

Before beginning to taper off after midnight and during the predawn hours of early Wednesday morning.

 

 

And ending prior to the Wednesday AM commute.

 

 

While it the Wednesday AM commute should be manageable, it would be wise to afford oneself some extra time.

 

FIRST CALL:

 

 

Looking Ahead to Potential Weekend Storm

 

After the period of snowfall Tuesday night passes, all eyes shift to late next week into the weekend, as the PV lobe splits and a 50/50 low and potential east coast storm.

 

 

 

[40/70 Benchmark]

Final Call for Fast-Moving Tuesday Mess

Light to Moderate Amounts Expected

Synoptic Overview:

It now appears as though piece of energy pinwheeling around the PV lobe over southern Canada will amplify slightly more than originally anticipated in Saturday's First Call.

This amplification to the west of the area will trigger a southwest flow aloft, which will advect warmer air in to clash with the antecedent cold in place to proddice a period of precipitation.

 

The fact that the system now looks to amplify slightly more than originally anticipated will have two primary impacts on the forecast:

 1) Total amounts of precipitation will be slightly higher given greater warm air advection, which is the primary cause of precipitation in this instance.

2) Precipitation type issues will be more of a factor than implied with the issuance of the First Call.

Here is how the storm is now expected to play out.

Anticipated Storm Evolution:

Light snowfall should break out along the south coast later this evening and towards the Mass Pike:

 

And to the New Hampshire/Vermont borders by midnight, as snow becomes steadier and somewhat heavier to the south.

 

Snowfall should mix with and chance to rain over the islands by the Tuesday AM commute after up to an inch of snow, however, the vast majority of the region will experience a rather slow commute, so allow plenty of extra time tomorrow morning.

 

 

After 1-3" of wet snow, precipitation should have transitioned to rainfall across the rest of the cape by the end of the commute and will be mixing with sleet and rain along with south coast of New England.

 

The snow should rapidly begin mixing with sleet up through and north of the Boston area by midday, during the heaviest burst of precipitation.

 

And into southern New Hampshire before tapering off Tuesday afternoon.

 

 

While freezing rain should not be a major issue in this system, a small area across northern and central Connecticut may experience some noteworthy glazing. through midday Tuesday.

Final Call:

 

First Call: Saturday January 13th @9PM:

 

[40/70 Benchmark]

Verification of Tuesday Mess

Overall Well Forecast Event 

Here is the Final Call pertaining to Tuesday's messy event for review.

 

Versus what actually transpired in terms of snowfall.

 

While this was a quality forecast overall, there were a few blemishes. Firstly, a few amounts over interior southeastern Mass, the immediate Boston area and northern Rhode Island exceeded the depicted 1-3" range and some icing actually was observed right down to the coast on the north shore. Secondly, the 3-6" range across southwestern New Hampshire, southern Vermont and the Berkshires proved slightly too aggressive, which left this region between two areas of forcing. An expansion of the 2-5" range northwest would have covered this area. The system became slightly stronger than anticipated, which triggered stronger mid level forcing further to northwest over northern New England, while the the lower level lift the warmer air aloft overrunning th colder air at the surface was positioned across much of southern New England.

 

Final Grade: B+

[40/70 Benchmark]

Some Late Week Light Snow Before Moderation

Looking ahead through the Balance of January

 The coldest week of the season thus far looks to include one more chance for some snowfall across at least the southern half of the region later on Friday into very Saturday, as a second lobe of the polar vortex struggles to amplify in the wake of the first, which ushered in this current bout of arctic chill.

 

 

This could potentially result in a period of light snow from essentially the Mass Pike points southward beginning late Friday afternoon:

 

 

 

And perhaps periods of moderate snowfall near the south coast through Friday evening before departing the cape and islands after midnight early Saturday morning:

 

 

 

Light snowfall amounts are anticipated at this time with an update issued if necessary, however, major changes are anticipated.

 

 

Then the pattern begins to enter a period of transition into next week and beyond.

 

Moderation Expected Next Week

Guidance continues in strong agreement that the pattern will relax and temperatures will modify, as the polar vortex shifts into Greenland and troughing settles into the western CONUS.

 

 

 

 

 

This is consistent with passage of the MJO through Maritime phase 6.

 

 

 

 

However, the primary difference between this milder period and the stretch earlier in the season is that the higher heights should be focused across the northeastern CONUS, as dictated by the aforementioned tropical forcing. The is in sharp contrast to the period in December, in which a portent Pacific jet eradicated the entire North American continent  of cold air.

 

This means that while the pattern will certainly grow much milder, the cold air source will remain nearby and thus wintry threats cannot be ruled out. Additionally, it will not take as long to see larger sensible weather variation once the pattern changes, since the cold air supply will not be extinguished. This will be important towards the end of the month and into February.

 

February Sneak Preview

There are suggestions that later this month the cold air boundary will begin to press slowly southward as the MJO continues to travel through phase 6 and the extra tropical Pacific begins to respond:

 

 

This is where the plot thickens, so to speak, as the European ensemble and the Canadien ensemble suites progress the MJO into phase 7 near the onset of February.

 

This triggers the amplification of ridging over northwestern Canada, which aids in the faster and more proficiently delivery of cold. into the eastern CONUS.

 

 

 

 

 

However, the GFS ensemble suite offers a dissenting progression. It stagnates the MJO in phase 6, which would protract the more "gradient" like thermal field throughout the first week of February and delay the more drastic change until approximately February 7.

 

 

 

Given the fact that the first week of February is a very climatologically favored timeframe for highly impactful snow events across the region during warm ENSO years, this is a high stakes period, so it is important to consider which camp maybe more correct.

Tropical Considerations on Pattern Evolution

There is certainly a case to be made for either progression. It is apparent that the MJO has remained biased towards the Maritime continent this far this season given the residual cool ENSO GLAAM.

 

This could be considered data in favor of a slower GFS type of progression, however, this is not uncommon for the first half of El Niño seasons. Additionally, there has also been notable bias evident among guidance to be too lethargic with the pace of the MJO this season, which would favor a faster progression into phase 7. It seems more likely that perhaps the amplitude of the MJO in phases 7 and 8 may be modeled too great during the month of February. A weakening of the wave in these phases would be similar to the seasons such as February 1995 and 2007, which also featured a prevalent Maritime influence in the midst of residual cool ENSO GLAM/-PDO.

 

 

The continued progression of the MJO into phase 7 by the onset of February is also congruent with the forecast progression of the OLR, as it implies a progression of convective forcing out of the Maritime continent and towards the dateline.

Note the simultaneous decrease in vertical ascent in the Maritimes and decrease in descent over the dateline, which is consistent with a progressive shift west in convective forcing through phase 6 and into phase 7.

 

 

 

              Region 1.2   Region 3    Region 3.4    Region 4

10JAN2024     25.0 0.9     27.4 2.0     28.4 1.9     29.7 1.5

 In summer, while it seems likely that the GEFS suite is in error in delaying the progression of the MJO into phase 7, the amplitude of the MJO will likely be decreasing. Thus the 

hemispheric pattern may be more prone to extra tropical influences, which could mitigate a return to more wintry conditions in the mid latitudes should the polar vortex re-strengthen as some guidance currently 

suggests.

 

[inter]

What do you think about the Pac Jet going wild for the next few weeks and will that mitigate any winter weather in the region?

[40/70 Benchmark]

On 1/18/2024 at 4:01 PM, inter said:

What do you think about the Pac Jet going wild for the next few weeks and will that mitigate any winter weather in the region?

It will probably cause a milder stretch, but it doesn't necessarily mean the whole month of February is gone. I would be suprised. 

[SnoSki14]

15 hours ago, 40/70 Benchmark said:

It will probably cause a milder stretch, but it doesn't necessarily mean the whole month of February is gone. I would be suprised. 

This is not a typical Nino response. We might get skunked again 

[40/70 Benchmark]

35 minutes ago, SnoSki14 said:

This is not a typical Nino response. We might get skunked again 

We could....my concern is a 1973 type evolution. 

[40/70 Benchmark]

Light Wintry Mix Tuesday-Wednesday Ushers in Milder Week: Next Major Threat Looms End of Month

Messy Mid Week On Tap

Synoptic Overview

As is often the case, there will be a price to pay in order to transition the pattern from the very cold conditions of this past week. Indeed, the retreating arctic cold will remain in place long enough to ensure a wintery start to mid week precipitation, as implied last week. A modest parcel of energy will be weakening on approach as it breaks off from the amplifying western trough and around the periphery of the building Western Atlantic ridge in response to the deep Western trough.

 

 

Note the compressed flow between the departing polar vortex lobe that supplies the cold this weekend and the building western Atlantic ridge that triggers the warm up next week, which will act to shear the approaching wave apart. However, it may deposit a light snowfall over the northern half of the region and thus cause some slight travel delays from Tuesday into Wednesday before it dissipates and warmer air moves in.

Anticipated Storm Evolution

Mixed precipitation should enter the forecast area late Tuesday afternoon and evening.

 

 And continues as occasional light snow north of the Mass pike and mixed precipitation south of the Mass pike overnight into Wednesday morning.

 

 

Before ending as rain showers Wednesday afternoon.

 

And resuming as rainfall across the entire region with the next more potent wave on Thursday.

 

FIRST CALL:

 

A final update will be issued on Tuesday.

Looking Ahead to Major Late Month Storm Potential

The first of two potential major storm windows this winter was identified last fall as the period between January 23 and February 6. And while it is far from certain that this potential will be realized, there is strong agreement amongst the three main ensemble suites that a potent western ridge will amplify right in the the middle of the identified window of opportunity, on approximately January 30.

 

 

 

More updates will be provided as needed with respect to this potential over the course of the next week.

[40/70 Benchmark]

Final Call for Messy Wednesday AM Commute

Nuisance Level But Allow for Extra Time

There are no major changes from the First Call issued on Saturday night. This will be a light, nuisance level event that willl change to rain, but nonetheless, it will be slippery so plan accordingly.

 

Synoptic Overview

As is often the case, there will be a nominal price to pay for transitioning the pattern from the very cold conditions of last week to the milder stretch over the days to come. Indeed, the retreating arctic cold will remain in place long enough to ensure a wintery start to mid week precipitation, as implied last week. A modest parcel of energy will be weakening on approach as it breaks off from the amplifying western trough and around the periphery of the building Western Atlantic ridge in response to the deep Western trough.

 

Note the compressed flow between the departing polar vortex lobe that supplies the cold this weekend and the building western Atlantic ridge that triggers the warm up next week, which will act to shear the approaching wave apart. However, it will deposit a light snowfall over the northern half of the region and thus cause some slight travel delays from Tuesday into Wednesday before it dissipates and warmer air moves in.

 

Anticipated Storm Evolution

Mixed precipitation should begin over the  western portions of southern New England prior to the onset of the PM commute, by approximately 4pm.

 

 

Overspreading the balance of the area through the early evening.

 

And into the overnight.
 

Before beginning to taper off and transition to an icy mixture and rainfall during the predawn hours of Wednesday.

 

Precipitation should become more showery and sporadic in nature prior to the AM commute across the majority of the area.

 

However, there will undoubtedly be slippery spots that will remain, especially over the higher terrain north of the Mass pike.

 

There will be a lengthy break in precipitation during the day on Wednesday before a more significant round begins by Wednesday night, which will be primarily in the form of rain across the area.

 

 

FINAL CALL:

First Call issued Saturday January 20th at 9pm.

Stay vigilant throughout the week for updates on more important potential Sunday night into Monday-

 

 

[40/70 Benchmark]

Well Forecast Messy AM Commute

The forecast for the light snowfall event that concluded this morning was very strong. The only slight blemishes were were the fact that no place in the Monadnocks of southern New Hampshire quite made it to 3" and there were a few sports in southeastern Mass and this hills of northeastern Connecticut that received slightly in excess of 1" of snowfall.

 

 

FINAL GRADE: A

This minor system was a warm up for what will be a much more challenging forecast this Sunday. Stay tuned for First Call tomorrow.

 

 

[40/70 Benchmark]

First Call for Significant Sunday-Monday Winter Storm

Rain to Snow Transition with Worst Expected Overnight Sunday

Synoptical Overview:

A disturbance currently entering the Pacific Northwest will careen down toward the base of the residual west coast trough and towards a union with a sub tropical jet impulse moving through Texas during the day on Thursday.

 

 

 A ridge will begin to develop over the Western CONUS over the course of the next 24-48 hours, which will aide in the coalescing of energy from the aforementioned to two systems in the general vicinity of the Ark-La-Tex region by Saturday.

 

This burgeoning west coast ridge will be instrumental in the development of the impending storm system in three ways.

 

1) As mentioned, it will aide in triggering the union of the two systems to form a relatively formidable wave on approach this weekend.

2) It will allow yet another piece of energy from the northern stream to careen down over the crest of the ridge to interact with the storm and infuse cold air into the region this weekend, thus transitioning rain to snowfall.

 

 

3) This infusion of northern stream energy, while adding enough cold to trigger a change over to snowfall across the region, will ironically enough also act to ensure that the storm this weekend continues to move along and does not become a truly high-end winter event.

 

 

There remains some question of whether the interaction with the trailing northern stream energy supplying the cold, coupled with impacts from the confluence in the wake of the vortex near the southern Greenland will force this system out to sea to the south of the region. However, the current forecast philosophy is that the southern stream origins of this storm coupled with the significant phase change from negative to positive PNA in response to the building west coast ridge will allow this system to gain sufficient latitude as to impact the region in a significant manner. 

 

 

But any necessary changes to said philosophy will be addressed on Saturday with the issuance of the Final Call.

Anticipated Storm Evolution:

Light rain will begin to overspread the region on Monday afternoon, and. may be mixed with sleet and snow in the Berkshires from the outset.

 

 

 

Rain will then begin to mix with sleet and snow across interior southern New England Sunday evening.

 

 

And intensify overnight on Sunday and especially during the predawn hours of Monday, as deep layer Easterly flow transports moisture in from the ocean and produces some enhancement across the east facing slopes of the Worcester hills, northeastern Connecticut and northwestern Rhode Island.

 

The heavier fall rate of precipitation will expedite the transition of rainfall to snow to the coast by the Monday AM commute, as colder air continues to infiltrate the region. 

 

 

Expect delays and cancellations on Monday morning, as this will be the peak of the storm.

 

Any residual rain or mixed precipitation near the coast, cape and islands changes to snow by midday on Monday before precipitation begins to taper off from west to east during the afternoon.

 

And ends everywhere by Monday night.

 

 

FIRST CALL:

 

[40/70 Benchmark]

Final Call for Sunday-Monday Low to Moderate Impact Winter Storm

Rain to Snow Transition with Worst Expected Overnight Sunday Into Early Monday

Synoptical Overview:

 

 A ridge is currently in the process of taking shape over the Western CONUS. This ridge is serving to aid in the coalescence of energy from two systems in the general vicinity of the Ark-La-Tex region.

 

This burgeoning west coast ridge will be instrumental in the development of the impending storm system in three ways.

 

1) As mentioned, it will aide in triggering the union of the two systems to form a relatively formidable wave on approach this weekend.

2) It will allow yet another piece of energy from the northern stream to careen down over the crest of the ridge to interact with the storm and infuse cold air into the region this weekend, thus transitioning rain to snowfall.

 

 

3) This infusion of northern stream energy, while adding enough cold to trigger a change over to snowfall across the region, will ironically interact with the storm just enough to ensure that it continues to move along and does not become a truly high-end winter event.

 

At the same time, confluence to the south of the vary large vortex in the general vicinity of Greenland will be adding resistance to the progression of the precipitation once north of the Mass turnpike and especially the Vermont and New Hampshire borders.

 

This makes the snowfall forecast rather precarious because not only will the degree of cold infusing in from the north be marginal to allow for a significant snowfall, but so will the amount of lift making it far enough north as a result of the confluence. But be that as it may, the current forecast philosophy is that the southern stream origins of this storm coupled with the significant phase change from negative to positive PNA in response to the building west coast ridge will allow this system to gain sufficient latitude as to impact the region in a significant manner. 

 

 

And this means that the most favored areas for a significant amounts of snowfall will be the central, elevated areas of the Worcester hills and the Berkshires. 

Anticipated Storm Evolution:

Light rain will begin to overspread the region Sunday morning, and may be mixed with sleet and snow in the Berkshires from the outset.

 

 

 

Rain will then begin to mix with sleet and snow across interior southern New England Sunday afternoon.

 

 

And intensify overnight on Sunday and especially during the predawn hours of Monday, as modest deep layer East-northeasterly flow transports moisture in from the ocean and triggers some slight topographical enhancement across the east facing slopes of the Worcester hills, northeastern Connecticut and northwestern Rhode Island.

 

 

 

As alluded to previously, the highest confidence areas for significant amounts of snowfall will be the central, elevated areas of the Worcester hills and the Berkshires. This is because these areas are elevated and far enough north that the column should eventually cool sufficiently, albeit by a narrow margin. And these locales are also far enough south that sufficient lift to overcome marginal boundary layer is highly likely, especially considering that there should also be a slight upslope component.

 

 

The heavier fall rate of precipitation during this period will expedite the transition of rainfall to snow to the coast during the pre-dawn hours or early Monday morning.

 

 

 

 Thus the Monday AM commute should be a slippery one, as colder air continues to infiltrate the region. 

 

 

Expect delays and cancellations on Monday morning, as this will be the peak of the storm across eastern areas.

 

Any residual rain or mixed precipitation near the coast, cape and islands changes to snow by midday on Monday before precipitation begins to taper off from west to east during the afternoon.

 

 

 

And ends everywhere during the day on Monday, well in advance of the evening commute.

 

FINAL CALL:

 

First Call Issued Thursday January 25 @ 11AM: