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Tuesday, February 4, 2020

Some ice and even rain look likely Thursday night but big snowfall potential remains with this storm according to some just released model data

Consistent with the prevailing trend of the entire winter so far, it seemed as if another opportunity for a big winter storm has slipped from our grasp. The debate is not over however and the possibilities for a decent amount of snowfall remain in spite of what appears to be some unavoidable period of wintry mix or possibly even rain in the middle of all this. There are a few chapters in this story and it starts with arctic air, which will envelop Vermont beginning Tuesday evening and provide the MRV with a little bit of snow Tuesday evening and a wintry but dry day Wednesday. There will be some opportunity for a bit of sunshine Wednesday before clouds from the upcoming storm arrive very late in the day or in the evening.

There appears to be two opportunities for new snowfall from this storm bracketing what is certainly a troubling middle. The initial area of low pressure will approach Thursday and travel just south of the St Lawrence Valley. It will bring with it, a major league push of milder temperatures, but given the somewhat fresh supply of chill that will encompass northern Vermont Thursday morning, it will take some work to scour out the cold. The result will be a decent period of overrunning snow beginning around dawn and persisting through early afternoon. The snow should be heavy enough to bring a few inches of fresh powder before precipitation chances to sleet and then to freezing rain. The inversion, responsible for the precipitation change is no joke and is centered right around 3000-5000 feet above the surface (About the height of Mt Ellen & Stark). This will mean that summit temperatures will likely exceed readings in low lying areas for several hours Thursday evening.

With all that said, the latest version of the European model (just released around this update) has shifted south somewhat and is actually showing a COLDER storm verses the once colder American model. It's model chaos. This would limit the window for any freezing rain or rain Thursday evening and might amplify what we hope is 2nd period for decent snow on  Friday. The initial low pressure center will actually track a bit too far ahead of the associated jet dynamics and as the latter approaches the east coast, it will allow the storm to refocus its energy somewhere over Virginia. As this process takes place, the warm inversion will weaken and ultimately be eliminated and any rain/freezing rain will become snow Friday morning. The eventual track and intensification of the "regenerated" coastal low is pretty critical to snowfall amounts Friday and computer models are varying from a few inches to as much as a foot. I was certainly encouraged with the recently released European model however. Hope is kindled !

Regarding specific accumulations, the overruning snow Thursday morning appears to be of the 3-6 inch range to me. As mentioned there is more uncertainty with the snowfall Friday (after the freezing rain/rain) but higher potential.  For time being lets let the various models guide us to the 3-12 inch range and we can narrow this down over time.

Friday's storm will exit quickly and some sunshine should return for Saturday along with temperatures in the single numbers and teens. Blustery conditions should prevail in the morning but winds should dissipate by the end of the day. A weaker area of low pressure has a chance to bring some snow to parts of southern New England Saturday night into Sunday but for the time being this is expected to steer clear of Vermont though that feature might spread some clouds into the state for early Sunday. Sunday's temperatures will moderate somewhat by the afternoon but could start the day in sub-zero territory.

The jet stream in the Pacific continues to show signs of weakening over the course of the next week but I would hesitate to call it favorable (at least not yet). And we don't have any help from the PNA, NAO or AO which collectively leaves us with a bit of an uphill climb. That said, a ridge in the stream over the southeastern United States does appear as if it will confine its influence to the southeastern United States. An area of unsettled weather and relative chill is meanwhile indicated to position itself over the Labrador Sea. To me, this translates into a bit of a repeat of the current week. It's a horror show for winter weather over the Mid Atlantic states but Vermont and other parts of interior northern New England will have a chance at scoring more snowfall. We can and always will continue to hope.

1 comment:

  1. Josh...how does Thursday night look driving up 91 and 89 to Stowe?

    ReplyDelete