Wednesday, December 20, 2017

Steady snow Friday, no thaw Saturday and a Christmas Storm that looks more and more promising

Yesterday's update seemed rather inadequate in light of the rapidly evolving weather situation going into the holidays. There's a ton of new information that should help us pin down a few key forecast details in the short term, get us all jacked with lofty expectations for Christmas Day and then speculate as to how long we can keep this going. This is one of the better updates I HAVE EVER GIVEN so by all means, blame the messenger, it's a terrific time to do so.

Winter is re establishing itself across Vermont as of Wednesday and the airmass responsible for this will continue to strengthen its grip on the state Wednesday night and Thursday. Though discredited for several days, this airmass  is a very effective one since it will dam itself east of the various northeast mountain ranges by Friday morning which helps to enhance the overrunning precipitation that is anticipated for Friday. This is one of the more important details to clarify. There was dissension within the ranks of model info for a time but not really anymore, snow begins around 7 am Friday and should fall steadily throughout the day. Temperatures will also be colder than people are anticipating, remaining in the low teens throughout the day and into the evening. Lets be entirely unequivocal, Friday is a powder day with 6-10 inches of the good stuff falling by the evening. Some of the best forcing associated with this initial wave of moisture will clear the area Friday night and the snow will become less intense.

Things brings us to our next important detail. NO THAW ! Don't think it happens, not anymore. Temperatures will make a push into the 20's Saturday and any snow turns to freezing drizzle and eventually we are likely to see some freezing rain. Models have obviously evolved very quickly on this upcoming weather situation so it begs the question, does the evolution continue ? More simply, can we get rid of all the ice in this forecast Saturday ? Not impossible, but still not probable. I would still expect a glaze atop of Friday's snow.

Oh Christmas Storm, Oh Christmas Storm, what tidings bringest thou ? This is very tricky storm to pin down and still is, but one gets the feeling the Euro is starting to lock in on this sucker, a potential 1-2 footer for interior New England  and the Adirondacks beginning Sunday night and persisting through most of Christmas Day. Canadian is on the snow train also predicting the same for Christmas Day. Here's the caveat though, the polar jet is a ferocious animal and it has a tradition of crushing these systems. The Christmas storm will start as a wave along a front only slowly pushing east this weekend. A small change in the way the incoming polar jet interacts with this boundary could have profound consequences on this storm. It's looking better and better but remember, one run of models can give you lots of snow and the very next day they can take it all away. I'd say our chances for big snow Xmas are just north of 50 percent as of late Wednesday.

Still got big cold in the outlook for the middle part of the holiday week. A blanket of snow could set the stage for readings of 10 below or more on one or two nights before the arctic air is allowed to modify. Still expect the cold weather to sustain through New Years weekend with the possibility of another storm around the time frame of December 29th and 30th.