Thursday, December 29, 2022

Rapidly retreating arctic air and angry Pacific to bring a very mild week of weather to Vermont

Arctic air continues its end of 2022 North American retreat and temperatures across all of New England are poised to soar. Model data is suggesting a dry day Friday with a layer of clouds assisting at maintaining an inversion that would mitigate the warmth and the wind. I think this can be true for a chunk of the day, but even a small period with a break in the overcast will allow the excessive surge of mid-level warmth to mix down to the surface and allow temperatures to exceed 50 in valley locations and at the base of Mad River Glen. These temps along with the near 40-degree dewpoints will soften snow conditions and this should continue into Saturday when temps continue to hover in the 40's even during the morning. The rain is coming for the weekend as well and its just a matter of timing it at this point. Several hours early in the day Saturday should remain dry but the risk for rain increases during the afternoon and and we should expect to get wet before the end of the ski day. The heaviest rain can then be expected Saturday night followed by colder windier day Sunday with precipitation becoming a wet snow across the high country though  it appears to be too light to amount to anything of significance. 

The jet stream in the Pacific has decided to end 2022 in an especially angry mood and the results are not good for Vermont snow lovers. Across a corridor of the western United States, the results have been a lot better. Tahoe has had an incredible month but the recent storm saw rain even as high as 7000 feet. Mt. Rose is a cool family owned Nevada mountain and also has the luxury of having much of its skiable terrain above 9000 feet. Almost 170 inches of snow has already fallen at Mt Rose this season with more on the way. Utah and much of Colorado have done extraordinarily well this week and have enjoyed cool temperatures and excellent snow throughout this month. The mood  of the jet in the Pacific  is expected to improve over the coming week, but not soon enough to prevent another big surge of east coast warmth toward the middle of next week. Almost everything appears a bit quicker as of today verses some model indications a few days ago but that hasn't shifted the overall theme of the outlook for next week; in fact, the warm surge looks warmer and may result in record breaking temperatures (60 degrees in valley locations) across New England with a wind and rain event quite possibly wiping out much of our snow after Wednesday. I use the term possible because there's a more intriguing possibility emerging following the big warm-up and a period of rain that appears impossible to avoid. Could low level cold in Canada make a southward push out ahead of a lagging wave of flow pressure and induce a late week snow event late next week (Jan 5-6)? Slight chance for now but not yet likely.

As mentioned teleconnection indices all turn mildly favorable even before my targeted turning point date of January 10 save maybe for the NAO which as of today is indicated to remain just a little positive through the foreseeable future. For the time being however, longer range models are struggling to pull arctic air back into North America. There is evidence of some ridging in the arctic regions above the northeastern Eurasian continent and this feature would be capable of pulling arctic air back into the northern half of North America (most of Canada), but models are yet suggesting this feature to be strong enough to do this in a large scale way. Even without the presence of large scale amounts of arctic chill however, operational models over the past few days have indicated the return of winter weather between January 9th and 16th which is about as far out as we can see. As mentioned, a softer January pattern with a limited polar jet might be bad for snow along the New England and Mid-Atlantic coasts but is not terrible for interior and elevated areas which can be dominated by dry stable air in such an environment. We will need some time to recover after this stretch of warmth, but it continues to look at least a little promising for the final 3 weeks of January.

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