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Tuesday, December 11, 2012

Winter storm speculation begins

Exciting times have finally arrived making the colder weather feel that much more invigorating. Finally, we have storms (plural) to discuss and real winter weather to talk about. Lets also preface some of the details by saying that it is especially nice to see a succession model guidance cycles trend colder and snowier as opposed to what dominated last years SCWB headlines - warmer and rainier or just warmer and warmer.

Over the next five days there will be two important big picture developments. The first and I will say critical, is the westward progression of the "evil empire" in the Pacific. This large and destructive ridge will move west toward the date line and will allow the onslaught of storminess to shift south. The second is the westward movement and enhancement of a large upper ridge, almost a block, across eastern Quebec, Newfoundland and Labrador. Although this combination doesn't necessarily encourage widespread very cold weather, it does promote an active and southern storm track capable of producing moist systems which can ultimately get trapped along the New England coast or in the Canadian Maritimes. This is precisely what we can expect with the weather as we head toward next week. We still have significant concerns regarding the amount of available cold air but we are headed in the right direction and lets hope this continues.

This is a one-two punch scenario with the first system tracking through the plains and Midwest this weekend as cold air across Canada weakens with the remaining chunk settling over Quebec. The building ridge over eastern Canada will allow this lingering cold to ooze south ahead of the approaching initial weather system and it looks for now that potential precipitation should begin as snow Sunday evening the 16th. With several days still remaining before the start of this potential weather situation, a lot can still change, but there are good indications of a healthy moist conveyor with this initial system that could allow for an extended period of light to moderate snows into Monday. Such a scenario would certainly mean the first real significant accumulation of snow for the winter were it to hold.

The second part of the one-two punch is a much more dynamic system and could involve a large east coast amplification Tuesday into Wednesday (18th-19th). I consider this type of system a high risk/high reward event at this point because the potential, given an absolute ideal situation is for a massive snowfall. The risk however is that when such a powerful amplification occurs, with minimal cold air, so close to the warm Atlantic, there is little resistance to the eventual envelopment of warm air and a transition to rain. For now, I will be happy to see this first system evolve in the way it is forecast to evolve right now and hope the powerful ridge in eastern Canada works to flatten out this second storm somewhat,

Aside from the potential over-amplification next week, there are fewer if any threats for warm weather going forward to Christmas. The pattern does not support below normal temperatures but for the most part, respectable temperatures through Christmas day consisting of generally below freezing temperatures, at least in the high country.