Monday, February 15, 2021

Two storms will challenge northern Vermont with pushes of milder air but precipitation looks more like snow/sleet and less like ice/cold rain

The weather made a few headlines this past weekend as a historic cold wave descended on the state of Texas.   As of late Sunday, every county in the Lone Star State was under a winter storm warning and there were apocalyptic wintry scenes from around Dallas which experienced blowing snow with temperatures in the teens. Now we've had some snow this year in and around the MRV and we are about to get more this week, but much of Texas has us beat for wintry weather this past weekend so congrats to them on that. 

This weather pattern overall is quite extraordinary because of the intense cold in the central U.S. but it does bear a resemblance to a pattern I might expect during a significant La Nina winter (certainly a more extreme version of it). Arctic air battling it out with a stubborn and resilient ridge in the jet stream across the southeast and don't forget about all the storminess that has impacted the Pacific Northwest. That storminess is taking quite the scenic route across North America right now entering via the Puget Sound, heading southeast all the way to the Rio Grande Valley and then making a hard left turn toward the Ohio Valley. Two storms will do that this week and the tracks of both significant storms will bring with them a big push of milder temperatures. I think we can keep the sub-freezing temperature streak alive and keep the ice and rain away but we will certainly be challenged and twice ! 

Storm #1 is the one responsible for all of the snow in Texas and it will race northeast Monday toward eastern Tennessee and ultimately position itself close to the New Hampshire seacoast by midday Tuesday. This is a pretty good track honestly but we are working with a bare minimum amount of cold air. Most of it is to our west and not to our north. It should be enough however to allow for some light snow to develop during the afternoon Monday followed by some steadier snow during the overnight hours. Now as of late Sunday, we didn't have any more room to spare in terms of keeping this storm all snow. In other words, northward shift is now bad and even another 10 miles might be bad and with the overnight round of forecast data arriving as I write this, it looks like enough warm air might infiltrate a small layer of the atmosphere to change precipitation to sleet Tuesday morning. We can handle sleet but we need to keep the ice away and I think that will be a problem in southern Vermont, Mass and portions of interior CT. As far as accumulations go, the introduction of sleet to the forecast suggests lower amounts overall in the range of 5-10 inches. 

We get the remnants of the the midwest cold wave for 2 days Wednesday and Thursday. It will arrive abruptly shortly after Sunset Tuesday and should be accompanied by some snow showers for a few hours. The snow will be mostly gone by Wednesday morning but temperatures will be back around zero degrees and we should see a period of sunshine, a rare glimpse in a very active week. 

The news for the event late Thursday into Friday is encouraging right now. Another big amplifying storm in this pattern is certainly capable of cutting right to the eastern Great Lakes. The Thursday system will attempt to do that but the last few rounds of model data are indicating a much healthier cold air damming signature along the east coast stemming from the aforementioned airmass arriving Tuesday night. There is continued uncertainty regarding the exact track of this stronger looking storm late Thursday but I expect a front end dump of snow regardless of the track and then we have to root hard to keep the ice and rain away. Data today suggests that we have a very good chance of doing just that but a period of sleet continues to look likely. The eventual track of this system is critical and the ability for this storm to make an efficient transfer to the coast will determine whether or not we can avoid all the adverse stuff. The cold air damming signature was very encouraging today but we aren't quite to the finish line yet. In terms of timing with this storm, snow would begin late in the day Thursday and the best chance for sleet would be in the hours around midnight Friday. 

Colder weather and snow showers will ring in the weekend and are likely to continue through part of Saturday. Temperatures will below normal but remain in the more garden variety category rising into the 20's during the day and dropping into the teens and single digits overnight. The pattern certainly looks to be more Pacific and less Arctic for the last week of February but Vermont continues to look well positioned to escape any thaw and should be able to procure a bit more snow between Feb 22-25.


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