Wednesday marks the last day in what has been a long stretch of sub-freezing (in most cases, way sub-freezing) temps on the upper mountain. It's certainly been a good one with plenty of sunshine and calm winds. Thursday will feature more clouds but a mild wind will pump warm air into the region rather effectively and temperatures will push into the 40's, even way up on the mountain. Fortunately, Thursday is relatively rain-free. We may see a few sprinkles here or there, but there are no indications of significant areas of precipitation. This all changes of course Thursday night into early Friday as a somewhat split, but formidable weather system approaches from the west. More or less, this is the same storm responsible for the mudslides in California and it will pick up additional moisture from the Gulf of Mexico. Given the warmth, this isn't exactly good news. Rain will begin in the very early morning hours Friday, get rather intense during the morning hours and then taper off during the afternoon. The mild erosive wind will continue, pushing temps in to the 50's in some areas and damaging the snow pack. It won't all go away but a half to 3/4 of an inch of rain, high dewpoints and wind can do some serious damage. Fortunately the rain will be over by Friday evening and arctic chill will push readings downward Friday night.
Our storm will have a 2nd act in a two part series - an even stronger area of low pressure that is expected to bring it's precipitation after arctic arctic air is somewhat re established over Vermont. This 2nd area of low pressure is expected to track northeastward either across Vermont or somewhere closer to the southern New England coastline. We would strongly prefer the latter option but this is a critical question that remains not completely answered. When precipitation re commences early Saturday morning, temperatures profiles in the lower troposphere suggest it will be primarily sleet with some freezing rain. As the day progresses, this precipitation will gradually change to snow and we should see a period of that before Saturday night. The extent of the snow depends heavily on how far south, this 2nd low pressure area decides to track. An optimal track, close to the southern New England coastline, will bring us several inches after some morning sleet. The consensus of information suggests a hefty sleet accumulation and only 1-3 inches of snow. In any case, a big sleet accumulation isn't the worst thing following a thaw/rain. We'll get another layer on the foundation and hopefully go from there.
We get back into the cold for a time following our series of precipitous days; in fact, the cold looks far more impressive than the various long range indicators suggested a few days ago and especially a week ago. As it turned out, the demise of the jet stream ridge across the Yukon was greatly exaggerated. Though it looked as if it would be part of the general weather picture, its overall impact was downplayed by the longer range ensemble simulations. In the case of the European Ensemble simulations, it will prove to be one of the biggest temperature busts I've seen. In Vermont we will see a series of days with high temperatures only in the teens and low temperatures below zero. Not quite the intense chill felt a few days ago but still below normal climatologically speaking. There's also a weather system to watch, a clipper, that will advance into the Great Lakes late Sunday into Monday and potentially impact the east coast on Tuesday. This clipper is associated with a potent jet stream impulse, one that has the capability of working a bit of magic along the east coast. The impact on Vermont remains to be seen but it's worth watching.
The cold weather lingers through Thursday the 18th and then we anticipate some further tightening in the jet across the Pacific allowing the evil empire to emerge. There are levels of "bad" however and over the last few days the impact of this rather adverse pattern appears less bad. The Arctic and North Atlantic Oscillation (AO and NAO) will remain neutral to even somewhat favorable and when takes a measure of this "Evil Empire" through the lens of the MJO/EPO, it certainly could be worse. The EPO is only moderately positive and the MJO, though not in the most ideal phase of it's cycle, could be worse. It's very important to keep the competing forces around as opposed to getting overwhelmed with an extremely negative one. It looks more and more as if we may in fact do that meaning any thaw will be very minimal while at the same time not entirely killing the prospects for new snow.