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Tuesday, January 5, 2016

Lots of weekend storm details and much much more in this expanded update

The mountain is basking in some sunshine and enjoying a much more wintry setting. A tip of the cap to those who have managed to earn their turns the hard way. For those awaiting lift operation, we are probably one big storm away from such discussion and the opportunity for such a storm comes in the weather situation that presents itself to us this weekend. Though the possibility remains for a big dump, I have lost some enthusiasm for this this event since there are some problematic missing ingredients, some timing issues and possibly some storm track issues.

We have an initial storm in the plains late this week which will more or less tap itself out. A wave of low pressure along the east coast tries to get organized Friday night but ultimately fails. In spite of all that, clouds will be on the increase on Friday, the 2nd of two days where temperatures should get close to the freezing mark. Limited moisture should be able to work its way into Vermont Friday night allow for a period of light snow either during the overnight hours or early on Saturday amounting to an inch or two. Temperatures will be sub-freezing by a degree or two but the snow will be more wet than powdery. There is a very weak supply of cold and dry air which will help keep temperatures under the freezing mark for a while Saturday. This thanks to a weak jet max over the maritimes of Canada. The 2nd more potent storm organizing near the Gulf Coast needs a more ample supply of cold and since it doesn't really have it, will need to track in a very optimal way for Vermont to get a big storm.

I have been waiting got the models to more or less establish some consensus regarding this system but as of Tuesday afternoon we have yet to see it. The U.S. modeling from the GFS has been atrocious, only occasionally acknowledging the potential strength of this Sunday system and in many cases taking a flattened wave out over the ocean with little resulting precipitation for any east coast locations. This is proving to be and will continue to be an embarrassing problem for the American GFS model this winter which will, in too many instances, fail to adequately quantify the potency of the jet stream in the lower part and more critical part of the mid-latitude northern hemisphere. Given the strength of the El Nino, this part of the jet stream becomes exponentially  more critical and rarely is entirely overwhelmed in a split flow set up. Yet that is what the GFS consistently shows and will be consistently wrong in such debates with other models.

Three of the other medium range simulations show a major system gathering strength along the Gulf Coast with the entire jet stream amplifying behind it. There is a lot of fuel for this storm, both from the jet stream and from both Gulf and Atlantic Ocean moisture. With the cold air all focused behind the system however, the track of this storm needs to be utra-favorable. Canadian modeling showed a big snow event, the british UKMET hints at such at least to a lesser degree. The European model and it's associated ensemble members not so much. Specifically, the European Ensemble mean has shifted the track of this system westward with low pressure center moving through central New York state and into eastern Quebec. We aren't far from the good stuff, but precipitation would go to ice and subsequently rain later Sunday given such an outcome. Even a blend of the various solutions, excluding the garbage modeling from the GFS, suggests a miss on Sunday. There still is a decent chance but I would put the odds 70/30 against at this point.

What we will see is some snow in the wake of the passage of this system Sunday night and Monday. Arctic air will be establishing itself over the eastern part of the U.S. with the vortex of cold at jet stream level moving south to the lower Hudson Bay and later retreating during the middle part of the month. Weaker systems rotating around the aforementioned vortex will bring periodic snow to the mountains. Terrain enhancement and an unfrozen and relatively warm Lake Champlain will help produce what should be some respectable snow totals across the high country. Might only be a few inches at a time but this should happen on multiple days.

There has been a lot of debate surrounding the evolution of pattern during the middle part of January and beyond. There is no doubt, some of the teleconnections that typically drive eastern U.S. and specifically New England cold will weaken between the 15th and 17th. We will certainly lose the support of the PNA or any large ridge in western North America. We will have the benefit of a loosened Pacific Jet next week allowing for the outbreak of cold weather but this jet stream is expected to re-tighten somewhat (it's hard to keep that completely down in a El Nino) mid month. I don't argue any of this but the MJO does not support a complete EPO flip. In addition, we should continue to see some limited blocking near the poles preventing the pattern from going entirely warm. In my opinion, we should see lots of storminess so even if the event this weekend doesn't materialize as we would like, we should see additional chances during the middle part of January and beyond with temperatures closer to normal if not slightly above normal.

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