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Wednesday, January 27, 2010

Burst of snow late Thursday and a wintry next week

Although still lacking in moisture, short term model guidance has indicated that Thursday's clipper is much more intense dynamically. This system will spread clouds over MRG Thursday and eventually snow Thursday afternoon and into the evening. The clipper is associated with a sharp arctic boundary which will pass overnight Thursday but until it does it will snow and it should do so modestly for a short period late Thursday. Accumulations will range from 3-7 inches and be somewhat sensitive to elevation. This turns Friday into a powder day but be ready for cold of the more intense variety. MRG has managed to dodge some of the most intense cold of the season so far but Friday's chill should rival the coldest of the season with temperatures hovering around zero and wind chills well below that. The clipper system is our event for the weekend and should make Friday the most powdery. We had been watching a system down south but we will have to, cautiously mind you, assume this system tracks well to our south. The result is a mostly dry and very cold weekend with temperatures below zero both mornings and high temperatures near 10. Clouds and snow flurries will return Sunday but should not amount to much in terms of accumulation.

The cold blast will continue into early next week and actually be re-enforced somewhat early Monday. This means maybe some minimal amounts of snow Sunday night but mostly cold weather and temperatures well below zero at night. I had mentioned the that the storm track will at least temporarily shift north next week and this is indeed the case. It will put the region more in the range of some of the better "frontogenetic" forcing and when the next system exits the Rockies early next week it will take more direct aim at MRG. It is uncertain how much moisture will be available for this feature but it will no doubt be plenty cold and the possibility for a modest 4-8 inch dump around the Wednesday time frame of next week is reasonable. The passage of this system will ultimately allow temperatures to begin to moderate late next week and by the following weekend the arctic air will grow stale and lose its grip on the region.

There will be another much stronger system toward next weekend to watch. It will be a product of the southern branch once again and will arrive as the cold air weakens. Because the polar jet will deactivate so rapidly we will need the southern branch to do all the magic with this system and will also need to hope enough cold air can linger and we will need a relatively favorable tracks. Its better than a long shot that we receive a snowy impact from this system but it is a long way out and a lot can happen with so many uncertain variables.

Ensembles are showing a very strong signal for blocking but this block will be centered from the southern tip of Greenland west to the entire eastern half of Canada. The block also will not get support from the PNA which will mean that arctic air will make a big retreat. Weather systems after the first week in February will be controlled and steered by the southern branch and it might prove difficult to get weather up into New England. I think the threat of rain is minimal but the weather could dry out substantially after February 8th and a long period of tranquillity could prevail across the region.

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