Big pattern shift poised to bring multiple weeks of cold and snow to Vermont ski country

Wish the blog could start this way every year ! Though the month of December will begin on the mild side, a very decisive drop in the Arctic Oscillation index over the next week to ten days teamed with a large upper ridge in western North America (+PNA) should bring a December weather weather extravaganza for at least two weeks. We haven't seen a set up this good in December since 2010 and though it will be difficult to pinpoint  the best days for "powder", we will get our share over what I expect to be a 2 week stretch of favorable weather beginning December 7th.

A series of rather "blah" days will kick off the month of December. Temperatures will remain mostly below freezing at night and get close to or slightly above freezing during the days. Sunshine will be limited and skiing in Vermont will likely be confined to the usual early season arteries. The early part of the first full week of December will feature a pattern poised to explode. Arctic air will enter the northern Plains and flood the Front Range corridor. As this happens milder air will make its way northward into interior New England. The entire state will likely see an extended almost 36 hour above-freezing stretch accompanied by a few hours of rain later Tuesday. When readings do finally fall back into the 20's late on Wednesday, it will begin what I expect to be a very long stretch of sub-freezing weather and a terrific opportunity to begin establishing what we hope to be a healthy 2017-2018 base.

Though we likely see some flurries late on Wednesday and more snow showers Thursday, significant snowfall might wait until at least at least the weekend before reaching the state. Relating to this upcoming cold pattern, the question relates whether or not we see much of a southern branch of the jet stream. The strength of the building La Nina suggests likely not. We will need a portion of the jet stream in the Pacific to undercut the large ridge in western North America and this kind of thing doesn't usually happen in La Nina years, at least not a lot. That said, we can still see plenty of fireworks along the Atlantic Coast and clipper systems galore. The unusually warm water situated in the Great Lakes and in Lake Champlain actually provide a rather exciting thermodynamic environment when the arctic air attacks. We might start slow, but we will see some terrain enhanced snow and substantial amounts of lake enhanced moisture. There are hints of something along the Atlantic coast during the weekend of the 9th or 10th. Though models were a bit more bearish as of late Thursday (Dec 30th), subsequent runs may very well show some activity and my guess is that our first few significant inches fall over that weekend and perhaps as early as Friday the 8th.

Re enforcing blasts of cold arrive in the December 10th-11th period and both cold and winter weather should dominate the ensuing week through what we hope to be opening weekend on the 16th/17th of the month.  A significant storm is possible during this period though I expect that a good chunk of snow falls as a result of a series of smaller systems, clippers and lake and terrain enhanced snow. I'll take it anyway we can get it, should be a great start to the year  !