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Tuesday, December 24, 2013

Arctic chill looking for a long tenure at the throne

We took a few good upper cuts from the recent thaw but we did make it through. Perhaps I should try anesthesia for the next thaw because mentally, its rather tough to watch good powder go to slush and then crust. The cold weather is back in a big way though as temperatures on the mountain will hover near 10 degrees during the afternoon of Christmas Eve and Christmas day and should fall below zero Christmas morning. Aside from some snow flurries, enough perhaps for a dusting, it should be a relatively dry two days on the mountain. The next chance for accumulating snow comes Thursday from this clipper we have been watching. We continue to hope that as this system swings through southern Canada, it can tap at least limited amounts of Atlantic moisture and deposit at least a few inches of snow on the mountain (because we need it). The European model continues to be the more vibrant solution regarding this storm and even this result would generally suggest less than a 1-4 inch event for the 26th into the 27th. The Canadian and American models show a meager dusting to an inch or two. 

The cold weather will remain in place for the first part of the weekend but temperatures could actually sneak above freezing Sunday given enough sunshine. After snow flurries and a few snow showers Friday, most of the weekend will be free of snow or any precipitation. The warm day Sunday will occur as the overall weather pattern re-aligns itself into one that will, for the first third of January produce a large amount of brutally cold arctic air into both the Great Lakes and New England. Given what we have seen from the intensity of these air masses so far this winter, it is a good bet that readings will nose dive into the -10 to -20 degree range on 3 or 4 of these first 10 days of January. The culprit is will be development of a weak to moderate positive-PNA pattern which will align itself with what we expect will be a weak to perhaps moderate negative AO. The PNA magnitude (although it isn't actually measured this way) can be loosely measured by the strength of the ridge in western North America. So far this winter, we have not seen much of a ridge in that part of the continent and Vermont has been cold in spite of it. By the new year, we are expecting a ridge to develop over British Columbia and this will focus much of the unmoderated arctic cold over Vermont and other nearby areas.

Of course, we need snow to go along with this cold. Another clipper system, which will arrive late Sunday into early Monday, will bring the next chance for snow to the mountain. This system marks the first big intrusion of cold in the newly aligned pattern. After that, much of the energy in the jet stream will shift south as will the storm track. If it doesn't shift too far south, it opens the door for future clipper systems to continuously deposit additional snow and one of those could evolve into a more significant  snow producer given some constructive interaction with the Atlantic Ocean.  To get a big monster storm, we need the flow to split underneath the positive PNA in the west. This would allow southern branch energy to undercut part of the pattern (without destroying it) and the result would be a steady stream of 1-2 footers like we saw in 1993-1994. No indication of that, at least as of yet but we do still have the door open for terrain induced and Champlain induced events that will also make a contribution during the early part of 2014. 

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