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Monday, February 17, 2014

Snow prospects look better, while thaw looks brief and less intense

SCWB entries have been full of good news over the last few weeks and it was expected that the positive vibes might end with the current entry. From a certain point of view I suppose that is so, but from my point of view, weather and forecasting is relative. One expects a certain narrative to play out but when the narrative changes our reaction is based on the nature of that change as opposed to the specifics of the story. At least that is the way it works for me. The end of the upcoming week had and to some degree still has a foul stench to it that one could smell even a week ago. Successive cycles of models have rather significantly mitigated much of the odor. One could speculate as to the reasons why this potential ugly thaw doesn't look as bad. My feeling is that there are two major feedbacks working in our favor and should be for the duration of the season. 1) A massive expanse of snow cover over the Midwest and Northeast 2) A remarkable coverage of ice in the Great Lakes. The latter is particularly noteworthy. 4 out of 5 of the Great Lakes are about completely frozen with Lake Ontario being the last hold out. You have to go back at least to 1994 to see anything remotely close to a situation like this. With much of the Great Lakes ice rather than water, the aggregate lake environment does not have the same impact on the weather map that it would in a typical winter. In the end, cold air masses are consistently winning small battles against surges of warmth and over time, these results make a difference.

Over the next week, almost everything on the weather map looks farther south. We are still expecting a dose of  snow from a "fun of the mill" weather system that should spread the powdery stuff into Vermont early Tuesday. This storm marks a division between very cold arctic air and eastward advancing and milder pacific air. In the end we should see 3-6 inches from this period of snow which should end Tuesday evening. Tuesday's temps will mostly be in the teens. Wednesday will be substantially milder, closer to freezing actually but a weaker disturbance will keep clouds in the region and more snow, maybe even an inch or two. Amazing, but a day that looked very much like a very mild day, now could at least partially turn into a powder day. Thursday will dry and above freezing temperatures in the afternoon should finally remind us that March is just around the corner.

What's left of the "odorous" stank occurs Thursday night and Friday. By this point a large upper ridge covering the eastern half of the country will guide a well organized storm system deep into Quebec. Rain or freezing rain should develop Thursday night and we should certainly see a period of all rain Friday, at least a half an inch of the liquid stuff. Temperatures could briefly surge from the 30's Thursday night, all the way to 50 Friday but the mild intrusion will actually be short lived and colder weather will begin displacing this warmth by Friday evening.

Models have been hinting, several times actually, at a storm for the weekend of the 22nd and 23rd. Although the warm ridge gets beaten back late Friday it will not disappear entirely. A storm system will again be guided up the slope of this upper ridge somewhere in the vicinity of New England. A few days ago, this appeared to be the second part of a potentially damaging thaw and perhaps another rain event. Again, in the last few days everything looks farther south and as the jet loosens in the Pacific by the 22nd, cold arctic appears like it wants to make a more efficient southeast advance, perhaps fueled by some of the feedbacks discussed above. If the cold proves to be a significant player in this evolving weekend event, and there is every indication that it will be just that, precipitation from this storm has a much better chance of falling as snow. As of now, models are still having a tough time with this system and whether or not it exists at all. As of now, I am certainly a lot less worried about a 2nd round of rain.

Cold weather fueled by the reemergence of a positive PNA and a loosened jet in the Pacific will likely dominate the back 6 days of February. Beyond the weekend, we could see some more snow from either a passing clipper system or simply from terrain induced snow showers. During the last day or two of February into very early March there are some more signs of splitting in the flow and some resulting active weather.

1 comment:

Christine Allred said...

This freak surge of winter seems to be unrelenting. Imagine what this means for homeowners and the repairs they might have to do afterwards. Hope the heater holds up, though I guess repair and backup options are always available.

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