Think Snow, Tweet Snow !!!

Sunday, January 8, 2012

First extended period of "Winter" comes after Thursday/Friday event

Aside from a little snowfall Monday night, amounting to an inch or two at best, we will now focus our attention on the Thursday/Friday system. This particular storm has all the makings of a beauty for MRG. Its got moisture from the Gulf and will track right over southeastern New England. As mentioned in the last update however, it has little cold air support. Much of it will have eroded and forecast temperature cross sections will be very marginal when precipitation begins early Thursday. Marginal does not necessarily mean rain, it is actually very close. Temperatures in the lowest 6,000 or so feet of the atmosphere will be within a degree or so of freezing and a shallow layer of below freezing temperatures at the surface may allow for a prolonged period of a sleet/snow/freezing rain mixture. Not ideal skiing weather and certainly not a powder day Thursday but that kind of stuff is good base building material and I would certainly take a few inches of that over rain. As you move north along the spine of the Green Mountains, chances improve for precipitation to be more snow less sleet. Jay Peak, as is the case many times, will likely triumph.

The system traveling through southeastern New England Thursday is the first of two significant pieces of energy capable of delivering the region precipitation. The second is polar jet energy which carries with it less moisture but its arrival will bring both colder temperatures and what appears to be a pool of instability capable of producing a period of some terrain induced snows Friday. At least a few inches are likely ahead of what should be a winter-like weekend with well below freezing temperatures and perhaps more snow showers if we are lucky. All of this comes as the AO makes its awaited switch, the switch that will finally allow winter to make an extended stay into Vermont.

The model guidance has been very inconsistent after the upcoming weekend. The global picture however makes a little more sense. The biggest feature on the weather board is a "blocking" ridge which will extend up from the Bering Sea to the Arctic regions. This should force much of the cold into North America but it is tough to discern where the focus of this cold will be. Ensembles show that some of it travels in to places such as Vermont while a bulk of it will wind up in the Pacific Northwest by the 18th or 19th of the month. With the polar branch of the Jet occupying mid-latitude North American it might be difficult to get Gulf or Atlantic Moisture into many of the passing weather systems. The Jet energy from polar regions often thwarts such attempts but fast moving clipper systems will still bring powder to the region at least twice between the 15th and 19th of the month.

It gets a little tricky after the 19th as much of the Ensemble data points toward colder, more active weather in western North America, a faster and more energetic Pacific Jet Stream and a relaxation of the cold in eastern North America. The AO will remain negative but will be forced to compete with the PNA to win over Vermont and the rest of interior New England.

1 comment:

Curley said...

Love your blog Josh, but I'm drooling for an update!!!