Arctic air shifts west...

and in a word this is discouraging. We have been in a generally favorable pattern for the better part of 3-4 weeks and many of the low lying areas of Vermont remain snowless. As we head toward opening day, the immediate horizon has the coldest weather so far this season arriving Sunday night into Monday but it precedes a rapid warm-up and what will likely be several hours of rain on Wednesday as a large upper level ridge is allowed to retrograde from the Atlantic Ocean to Atlantic Coast. This was one of my concerns expressed in the last post but even I underestimated the precarious nature of the pattern and the speed at which the cold could be eroded.

There is a silver lining I just wish it was a bit brighter. The mid-week storm system this week is a moist one. As the push of mild weather commences, the region will pick up a few inches of snow Monday night into Tuesday. After what looks to be an unavoidable round of rain on Wednesday and temperatures in the 40's, a fresh infusion of cold air will arrive in front of what looks to be a second wave of low pressure. This could produce several more inches of snow during the day Thursday. If all goes well, the several inches of powder would be the last precipitation to occur before Friday. We just hope that any snow more than makes up for the rain and mild temperatures which is set to impact all elevations on Wednesday.

The westward shift in the arctic air results from a global shift in some very important upper level features. The biggest of which is the movement of a ridge which currently covers western North America but is slated to move rather briskly westward over Alaska and ultimately situate itself over extreme northeastern Russia by the middle of this month. arctic air, and plenty of it will therefore focus its attention on areas mostly west of the Mississippi River. Vermont will have to use every bit of its 44 N latitude and hope for the best. The ensembles have disagreed on the specific impact a strong western trough might have on Vermont. The american ensembles do indicate that an eastern ridge could be weaker and flatter and allow cold weather to maintain a loose grip on interior New England. Along with this would be continuous rounds of winter weather. A stronger eastern ridge however would open the door for an event like the one mid-week to repeat itself.

As early as December 14th there are signs of another mild push and another snow to non-snow event. And whatever happens between the 14th and 16th of the month will have a lot to say about what kind of skiing we will be dealing with going into the Christmas holiday. There is plenty on the table to analyze so lets give it a few days and see how things look then.