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Monday, December 16, 2013

Late December Christmas outlook - lots to cover !!

We have one solid blanketing of snow and a memorable opening day in the books at MRG, but time keeps on ticking into the future and there is a lot to contend with in this future. The first half of this December is one of the coldest starts to the month we have seen in a decade and the cold has occurred in spite of a pattern not entirely supportive of sustained cold or big snow. The prevailing upper air feature in the jet stream has been a blocking ridge in the Bering Sea. This is hardly the ideal position for such a feature but it nonetheless sent such an onslaught of arctic cold into North America that the pattern was more or less overwhelmed with cold much like it was in my favorite winter of 1993-1994. It is such an encouraging sign going forward (at least this winter) to witness arctic cold battle the prevailing pattern with this type of ferocity. In spite of this, we still have to deal with some of the variability that such a pattern was inevitably going to produce. 

We will see this variability manifest itself during the upcoming weekend but in the meantime there is plenty of cold air in place and an incoming clipper system that promises to bring some light snow to the Green Mountains later Tuesday. Light snow from Tuesday afternoon into the evening might amount to a very fluffy 2-5 inches, enough for a few fresh turns Wednesday but the density of this snow will be noticeably less than the almost 2 feet of snow already on the ground. This particular clipper system will have its energy swallowed by a developing coastal system which promises to bring eastern Maine some nice powder Wednesday. Mad River Glen might see some snow showers or at least flurries Wednesday and some more lighter snows Thursday as a boundary representing the warm push of air makes its way toward VT. I don't expect much in the way of accumulation after Tuesday night. 

This brings us to Friday and the weekend which could feature all kinds of weather, possibly lots of weather and as of yet medium range models have failed to develop any sort of believable consensus. We do know that the northern half of our Bering Sea ridge will get chopped off leaving a pattern closely resembling that of the dreaded "evil empire". This being a upper ridge in the mid-latitude Pacific. Lots of mild air will thus make it's way northward, particularly Friday and although some of the aging arctic cold in eastern Canada will fight for control of interior New England, it could get dicey for sure. At this point it seems like there will be an initial push of warm air which will reach parts of VT for Friday. Parts of the mountain could see several hours of above freezing temperatures and perhaps some rain or freezing rain although precipitation on this day appears to be minimal. Colder temperatures will make a rather feeble push south Saturday ahead of what could be a very powerful storm system which will gather strength in Texas Saturday and head in our direction. In this particular situation, it will prove very difficult for this weak area of cold to play defense against a storm heading for the St Lawrence Valley. That being said there are hints on the last round of model output that the storm will travel south of Canada and perhaps right over Vermont allowing the cold weather, at least at the surface, to maintain a precarious grip on the region. There will be copious amounts of moisture sent in our direction and precipitation Sunday is unlikely to be snow but rather sleet, freezing rain or just plain rain. A significant icing event is actually possible in such a set-up but hard to pinpoint for sure how possible as of now. If we do get accumulating snow out of this storm, it would be Sunday night or early Monday. 

This brings us to the all important Christmas week which has yet to get extensive coverage from SCWB (it  has been overshadowed by our recent storm). A somewhat moderated arctic air mass should envelop the region in the wake of our big weekend weather producer. The ensembles however seem to be keying in on another weaker push of warmth around Christmas day. The American ensemble package has been downplaying this repeatedly and has suggested a relatively normal week of weather with a chance for some of the white stuff around Christmas day as opposed to any milder temperatures. I hope the American is right but another mild day and maybe another rain/ice event is possible around Christmas day. I would be more confident of a more serious push of cold weather and possibly some snow in the days following Christmas and into that last weekend of December.  

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