Winter Outlook 2024-2025

[40/70 Benchmark]

2 hours ago, qg_omega said:

First call tonight?

How is your call for a incredibly warm winter going?

I think most would agree that I have no issue owning a wrong forecast (or hedge), so I'm not sure what your point is. I think my seasonal idea looks pretty good.

[40/70 Benchmark]

Back to Regularly Scheduled "Cold & Dry" First Half of January

Weekend Storm No Longer Anticipated Due to Sudden Reversal of Trends

It became apparent early on Sunday that there was a definitive trend amongst all guidance to no longer hold back southern stream energy. 

 

 

This would subsequently afford it the opportunity to phase, at least to some degree, on Friday with a descending parcel of northern stream energy. 

 

 

Thus fostering the development of a significant winter storm this weekend. 

 

 

 

The thought process was that this type of a trend being evident across all guidance to varying degrees within 4 days of the potential phase was definitive evidence that guidance had an adequate handle on the southern stream evolution. Thus the likelihood of at least an eventual partial phase was relatively high, which is what led the conclusion that an impactful winter storm was likely. However, as turns out, guidance in fact did not yet have an accurate portrayal of the southern stream.

 

Southern Stream Holding Back Eliminates Phasing Prospects

It became evident by early Tuesday morning that the expectation that the southern stream energy would eject early enough to link up with the northern parcel would be incorrect, as guidance began to rapidly reverse that trend. 

 

 

This reversal is likely at least partially due to models keying on on seperate northern stream piece of energy that would disrupt the western CONUS ridge at the precise time that it was to assist in triggering the downstream phasing and coalescing of energy that would facilitate the development of the east coast storm next weekend.

 

 

Ironically enough, this outcome is very similar to the original expectation from late last week that the first half of January would remain cold and dry.

 

 

Although it is rare for trends in guidance to completely reverse once within 3-4 days of lead time, it is not impossible, and the assumption of Eastern Mass Weather that this would not be case in this instance proved incorrect.

[40/70 Benchmark]

 

Cold January with Notable Lack of Major Snowfall Poised to Continue

Frigid Arctic Chill to Arrive on the Heels of Slight Snow Chance Sunday Night

Although the month of January has evolved somewhat colder than anticipated thus far, the chilly temperatures have not translated to much in the way of snowfall.

 

This was not entirely unexpected given that the Eastern Mass Weather Winter Outlook called for most of the above average monthly allotment of snowfall to come between January 21 and February 4th, however, there is a considerable amount of doubt as to whether that will in fact be the case.

 

Frigid Onset to Second Half of January Largely Unaccompanied by Snowfall

The latter half of January looks to begin in much the same manner that the first half evolved, with the exception of the fact that the airmass early next week will be the coldest of the season thus far. The combination of west coast ridging and blocking within the NAO domain will send the polar vortex on yet another journey southward during the coming weekend as it descends out of James bay and into southeast Canada. At the same time, a weak wave of low pressure will pass offshore on Sunday night out ahead of the leading edge of the arctic airmass.

 

 

 

While the bulk of the precipitation will remain offshore, it is not out of the realm of possibility that an inch or two of snowfall, perhaps up to 3" in some localized areas, could fall over especially the southeastern third of the region before it moves away and the arctic siege begins on Monday.

 

Thereafter, the cold will moderate thoroughot the latter half of the week as the vortex begins to lift away over the Canadian maratimes.

 

Then the final third of the month will represent a period of transition, as the polar blocking relinquishes its grip and the Pacific blocking reasserts itself. This will present an opportunity for a more significant storm system, as is the case with any period of mass flux.

High Latitude Realignment to be Accompanied by Latter January Storm Possibility

The expectation last fall was for the month of January to predominately feature plenty of high latitude blocking on the Pacific side that would be accompanied by a strong polar vortex, and thus a dearth of blocking over the arctic. However, while the polar vortex has in fact been appreciably strong, it has remained fairly uncoupled with the troposphere, which has allowed blocking within the NAO domain to remain rather prevalent, regardless. 

 

This may ultimately prove to be a case of delayed rather than denied, as there are signs that the appreciably strong polar vortex will begin to grow more coupled from the stratosphere down through the troposphere. What this will entail is a reconfiguration of the pattern in that the arctic will begin to neutralize (rising AO & NAO), while the greater heights reconfigure from the Atlantic to the Pacific side (descending EPO/WPO, ascending PNA).  A hemispheric realignment of this magnitude will represent the type of mass flux and teleconnection modularity that will enhance the likelihood of the development of a major winter storm. This is evident on the Atlantic side.

 

 

And the Pacific side between approximately January 23-25.

 

 

While this is in accordance with the January 21-February 3 window identified last fall for a heightened risk of a major winter storm, ensemble support continues to be relatively meager, and a track out to sea remains the most likely outcome.

 

 

Thereafter, the pattern moderates somewhat over the final third of the month, while also ostensibly becoming more conducive to increased snowfall throughout the forecast area.

 

However, this does not appear to be a favorable pattern for major east coast snowstorms, and the similarities of the pattern thus far to some seasons that have managed to largely avoid snowfall across the area with surgical precision can not be denied.

 

 

 

[40/70 Benchmark]

Plowable Snowfall Possible for Large Portion of Southern New England Sunday Evening into Early Monday

Weak Storm System Appears To Track Closer to Region

Synoptical Overview:

This weekend a parcel of energy will begin to be steered around the approaching polar vortex that will supply the bout of arctic chill next week.

 

It will then round the base of the vortex and turn up the coast, however, the primary difference from yesterday is that it now appears as though it will track closer to the region to the region as it passes offshore early Monday.

 

 

The obvious implication of this is that it would have a slightly greater impact on the forecast area overnight Sunday and into early Monday morning relative to expectation yesterday, and thus slightly more snowfall.

 

Expected Storm Evolution:

A separate, lead system will traverse the area overnight Saturday, with precipitation falling primarily in the form of rainfall and some mixed precipitation in the higher terrain.

 

 

The follow up energy, which is the system of interest, then overspreads the area on Sunday evening with snowfall across the majority of the area, and rain over the cape and islands,

 

 

Snowfall may be slightly heavier over the deep interior, as well as the immediate coast during the peak of the event due to mid level and low level frontogenesis.

The low level convergence along the coast will be in association with the coastal front, which will begin over the immediate north shore, Boston area and interior southeastern Mass Sunday evening, before drifting southeastward overnight.

 

 

 

The other area of potential banding will be attributable to some mid level deformation just to the northwest of the mid level low track, across the northwest Connecticut hills and into Worcester county.

 

Any rain and mixed precipitation over the cape and islands will transition over to snowfall, as the system begins to pull away during the wee hours of Monday morning.

 

 

The last of the snowfall should exit the cape prior to midday.

 

First Call:

 

 

Final Call will be issued on Saturday-

[40/70 Benchmark]

 

Final Call for Quick Hitting Sunday Night Snows

Slightly Heavier Amounts Expected

Synoptic Overview:

Currently a parcel of energy is beginning to veer around the approaching polar vortex that will supply the bout of arctic chill next week.

 

It will then continue to round the base of the vortex and turn up the coast throughout tonight and into tomorrow. There is no deviation to this portion of the forecast rationale. 

 

However, there is one subtle change from First Call issued Thursday that does have fairly significant ramifications for the Final Call. Note that the position of the approaching polar vortex was over James Bay in the above guidance from Thursday, as compared to today's output posted below, which has the vortex slightly further to the north, and more over bodily over Hudson's Bay as opposed to James Bay, Canada.

 

The implication of this further north position of the polar vortex is that ir would afford slightly more space for the energy rotating around its southern periphery and up the east coast to amplify and intensify slightly faster before exiting the area.

 

 

This would result in somewhat heavier snowfall than indicated in the First Call.

 

Expected Storm Evolution:

Snowfall should breakout outcross the region late Sunday afternoon and early evening from southwest to northeast. Precipitation may commence as a mix along the south coast, and rainfall across extreme coastal southeastern Mass, the cape and islands.

 

The low will begin to intensify more rapidly as it passes off shore later Sunday evening, which will cause heavier bands of snow to develop, especially just to the northwest of the nascent mid level lows. Where exactly the most intense and persistent banding develops will dictate which locales receives localized heavier amounts of snowfall, however the annotation below provides the best estimate.

 

Any residual mixed precipitation and rainfall will transition to snow before precipitation ends during the pre-dawn hours of Monday morning, as the system pulls away into the Gulf of Maine.

 

 

Final Call:

 

First Call Issued Thursday, January 16th @ 10PM:

 

[40/70 Benchmark]

 

Snowfall Forecast for Quick Hitting Sunday Night Snows Largely Successful 

Minor Forecast Discrepancies

Here is the Final Call for last night's fast moving winter storm (right) versus what actually transpired (left) in terms of total snowfall accumulations.

 

While the forecast overall was fairly representative, the most persistent banding ended up being over the Berkshires into southern Vermont, as opposed to northern Worcester country into southern New Hampshire. Additionally, slightly less snowfall fell versus the expectation over the eastern half of the region due to the slower arrival of the colder air relative to modeling, thus 4-7" would have been more appropriate versus the 5-8" range that was utilized.

 

Final Grade: B

 

[H2Otown_WX]

On 1/20/2025 at 3:42 PM, 40/70 Benchmark said:

 

 

Snowfall Forecast for Quick Hitting Sunday Night Snows Largely Successful 

Minor Forecast Discrepancies

Here is the Final Call for last night's fast moving winter storm (right) versus what actually transpired (left) in terms of total snowfall accumulations.

 

While the forecast overall was fairly representative, the most persistent banding ended up being over the Berkshires into southern Vermont, as opposed to northern Worcester country into southern New Hampshire. Additionally, slightly less snowfall fell versus the expectation over the eastern half of the region due to the slower arrival of the colder air relative to modeling, thus 4-7" would have been more appropriate versus the 5-8" range that was utilized.

 

Final Grade: B

 

You're pretty hard on yourself man. You schooled professional forecasters.. 5-8 vs 4-7 be damned.