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Saturday, January 24, 2009

"Active Pattern" appears somewhat less active but new snow should still be expected

We have hit a dry spell in terms of our natural snowfall. We have been in the midst of a chilly regime and this regime has allowed us to avoid the rain and ice for much of the month. According to the observations at the Montpelier-Barre airport, only 0.90 of liquid has fallen if you melt all the snow and sleet. Mad River's elevation has ensured that precipitation amounts have been a bit healthier on the mountain but still well below average. Although we do have some snow to talk about for the upcoming week it will not be enough to dilute the cold and dry personality that January 2009 has now attained.


Along with the cold, we should, with the help of some low level instability and a quickly moving disturbance, pick up a little snow Sunday night into Monday in the form of snow showers and flurries. It will not amount of much and it will precede a very cold and calm night Monday night and a calm and somewhat sunny day Tuesday. The storm we have been watching for a while on the forecast charts will be making its way across the country Tuesday. This is a much weaker storm than I was hoping for, mainly because it lacks the upper level potency necessary to generate any real excitement. It will be close enough to the Gulf to draw in some moisture but it will remain a "positively-tilted-frontrunner" which is another word for garden variety. The other problem is the track which appears to put us somewhat out of this storms main path. We should still get some snow out of this either Tuesday night or Wednesday but the actual amount will depend what part of the 100 mile north-south possibility range the storm takes aim at.

Late this upcoming week and the weekend
This initial storm system Tuesday night and Wednesday will mark the beginning of a brief period when the upper trough is situated in eastern North America as opposed to the west (the prevailing pattern). I was hoping the period might be a bit more fruitful since if you add some incoming Pacific energy into this situation one can cook up an east coast storm rather easily. This in fact may well happen as lingering moisture in the Virginia Tidewater combines with energy from a "Saskatchewan Screamer" around Jan 30 or Jan 31. The problem is, all this cooking looks to be too far east. The SCWB will be watching this one as the week progresses but the chances are a bit on the low side right now and my guess is for a period of snow showers Friday into the the early part of the weekend and a light accumulation. It will continue to be cold but not extreme with morning temperatures a few below zero fahrenheit and within a few degrees of 20 during the afternoon. On Sunday Feb 1, another clipper will be passing through the St Lawrence Valley. This system may mark a temperature moderation to follow and it may bring a few inches of snow although nothing noteworthy.

Mild and dry at the beginning of Feb ??
The biggest upper level feature in the western hemisphere (north of the equator) will eventually be a large block over Greenland which as I mentioned in a previous post will help to counterbalance the western trough and more active Pacific Jet. This block will migrate southwestward somewhat into the Davis straits and creep into interior New England. I remember a pattern like this around the time of the Super Bowl in 2005. It eventually evolved into a good pattern by the middle of February but this block, if it gets too close, can bring a round of mild temperatures to the region. Since we are talking about a block however, the risk of rain and ice remains relatively low however and its merely just mild and dry. Weather systems in such a pattern are often forced well under the block and become cut-off somewhere along the eastern seaboard. If these storms move far enough north it can mean snow for the mountains but I think this would be wishful thinking right now. The Feb 1-Feb 8 period may be safe from a big rain thanks to the block and negative NAO but my guess is that it turns out mainly dry with some above freezing days and below freezing nights (sounds a bit like March but we will see)

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