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Thursday, December 5, 2013

Widespread snow/sleet event for Monday will be part of a very wintry week

Our first significant widespread snow event across the northern part of Vermont will arrive Sunday night or Monday morning. This will be one small part of a very volatile temperature forecast over the next two weeks. The pattern is being anchored by a giant omega blocking ridge over the Bering Sea. This is sending plenty of strong arctic air southward, but most of it is going into the Plains and Rocky Mountains where many spots will see temperatures near record levels during the coming week. Some of this arctic air will move eastward but we will not be the focal point of cold in this pattern. 

We are set up to have a somewhat wintry upcoming week however beginning over the weekend when the first batch of arctic cold displaces the mild air that will dominate the region Thursday into early Friday. A dusting to as much as two inches of snow is possible by Saturday morning but the real system of note is a loose conglomeration of low pressure centers which will gradually move out of the Rocky Mountains later this weekend. Arctic cold will be well entrenched as this system approaches. One of the systems two centers will move toward the eastern Great Lakes while another cranks up along the Atlantic coast. This is a very garden variety storm but it will impact a broad area of interior New England with snow across both mountains and valley locations. Snow should arrive late Sunday evening or early Monday with the heaviest snow lasting not more than a few hours. Precipitation could end as some sleet or freezing rain later Monday. I would put this in the category of a 6-12 inch event with the mixed precipitation adding some density or possibly some crust to whatever falls. Quite possibly a good base-building event !

Another batch of the some of the intense cold centered across western North America will then build across the region during the middle of next week but will likely be rather short-lived. The Polar Vortex could actually get rather close to Vermont for a day or so, perhaps sending temperatures well below zero for the first time this winter season. A clipper system could add a light accumulation of snow to the region as well. The Bering Sea ridge and the lack of any downstream blocking in the Davis Straits or Greenland will allow the cold to escape rather quickly and this could set the stage for another mild week beginning around the 14th or 15th of December. A few days ago I was more concerned about a widespread outbreak of mild temperatures but I think lingering cold in Canada will compete for control of the weather in spite of the overall expected jet stream configuration. At the very least however, it is likely we see some more above freezing days in the week preceding the Christmas holiday. 

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