Saturday, December 12, 2020

We need to pull the big midweek nor'easter northward if northern VT is to get in on the action !

Some cold rain on Saturday and mild weather Sunday is not an especially exciting winter weekend in northern Vermont but the outlook going forward does have plenty of winter weather to speculate on. Incoming arctic cold is a certainty for the upcoming week but the snow is not. We managed to whiff on the weekend storm which tracked along the St Lawrence Valley and we are hoping not to whiff on the upcoming midweek event which is causing quite a stir in the weather forecasting universe because of its potential to deposit a foot or more of snow on portions of the I95 corridor. 

There are actually multiple weather systems that are of concern to the east coast over the next 5 days. The first on Monday will assuredly have no impact on Vermont passing over the Carolina and Virginia piedmonts and bringing a cold rain and some snow across the Mid Atlantic and extreme southern New England. The southward advancing polar jet stream is the primary culprit for suppressing this initial storm but the passage of the arctic boundary Monday night will bring flurries and snow showers, especially over the high country. We have a good wind direction for a few hours early Tuesday and a very unfrozen and mild Lake Champlain which should allow for some accumulation (1-4") early in the day before the dry air wins out. 

It is a very cold high pressure center (at least for the time of year) building over Vermont on Tuesday and this will keep temperatures in the teens throughout the day and allow readings to fall below zero for the first time this season Tuesday night into early Wednesday. This same area of arctic cold will wedge itself east of the Appalachian Mountains in advance of a gathering storm, giving the weather map the classic cold weather damming setup that a weather enthusiast such as myself salivates over. All the important players are there and most are positioned where they need to be for a big east coast snow event Wednesday into Thursday. The problem for Vermont is getting the storm and its moisture far enough north and models suggest this won't be easy. 

5 days ago, models were completely chaotic regarding the details for the upcoming week but they've manged to exhibit some rather impressive consistency the last few days regarding the potential midweek nor'easter. Unfortunately, that consistency doesn't involve northern Vermont getting much; instead, all the fun is along the coast. Before one chalks it up as another whiff, let me remind readers that the top 3 storms this century were all shown to be well south of Vermont within 3 days of the event. I will never forget the partly sunny forecasts in early March 2001 and much of ski country got over 50 inches of that partly sunny over the course of several days. The Valentines Day storm of 2007 and Ides of March storm of 2017 also made late northward turns and defying expectations 3-4 days out. It happens and there are reasons that it happens so although I'll call it unlikely, it's hardly impossible. 

I'll briefly discuss the outlook beyond the middle of the week and extending through the Christmas holiday and expand on this in a subsequent update. The fundamentals look about the same. We are battling the angry jet in the Pacific, but are getting some help from the -AO/NAO. I expect we will be discussing a potential event during the weekend of the 19th and 20th (next weekend). We will have lost a chunk of the upcoming week's cold weather by then but not all of it and thus have a chance of procuring a bit of the good stuff. Ensembles are then suggesting a roller coaster with seasonable temperatures around December 22 potentially giving way to a mild surge around Christmas Eve. This would be then followed by colder weather on Christmas Day and the few days that follow. It's not an ideal looking weather pattern around the holiday but I've seen worse. Let's see how we look in a few days

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