Friday, January 25, 2019

Possible storm Tuesday/Wednesdy of next week ahead of another big cold surge !

The deep snowpack largely survived the onslaught of rain Thursday and will now serve as a very durable base for the duration of the ski season. To put that base to good use however, we will need some additional snowfall and fortunately, we have some opportunities for that in what still appears to be a very wintry outlook going into early February.

Following the light accumulation as a result of Friday's snow showers, Saturday will follow as a chilly but mostly dry day with temperatures hovering in the low to middle teens. Though it looks generally cloudy Saturday, visibility should be improved compared to the past few days. Some light snow is expected to move back into the region early Sunday in response to a relatively innocuous polar jet feature. There is limited available moisture with this feature and a lot of what is available will actually hit areas farther north. Still, we could see a 1-3 inch accumulation along with some moderating temperatures (near 30) as Sunday progresses.

The Sunday feature is somewhat of a disappointment, but it will allow a limited amount of arctic air to rebuild across interior New England ahead of the next and more dynamic weather situation. The various model simulations are all over the place and understandably so given the approaching polar vortex, the seemingly uncertain impact of southern branch moisture and especially the overall track and development of what could be a rather strong storm. No point in hedging here at the SCWB so lets try and provide some clarity by sorting through this mess of information. Doubting the legitimacy of moisture in the southern stream, as the American GFS model continues to do, appears flat out wrong to me. The presence of such moisture will serve us in two ways. Provide more moisture for snow, which given this scenario, will commence on Tuesday and pinch off possible warm intrusion by focusing low pressure development and intensification farther south. There are still some questions regarding the track and eventual intensity of this system and the with PV approaching the northern Great Lakes, it won't take much of a change to shift this track. That said, I think we have some leeway and good potential for a sizable snow accumulation in the Tuesday/Wednesday time frame. Stay tuned on this one.

Then we have the "polar vortex" (PV) to deal with late in the week. There has been so much talk about this feature and a lot of it has been truly worthy scientific discussion. And then there has been the incessant hype, mostly from the twittersphere and a lot of that has been what I would call "attention seeking". This PV will get as far as the northern Great Lakes and then veer northeastward, providing the U.S. a surge of very cold temperatures but only across a limited portion of the country. Vermont, as we all know, is usually well-positioned to get its share of whatever cold surge comes south so although the southern U.S. will avoid the extreme temperatures this time, we will get our share late next week. For about 4 days starting late Wednesday, temperatures are likely to stay in that -10 to +10 range with fiesty winds providing wind chill temperatures in that -20 to -50 range.

Some flurries are possible during this cold period and a disturbance could provide an opportunity for some light snow late next week. For the most part however, the proximity of the PV usually provides some stability to the lower troposphere and will keep a low ceiling on snowfall potential. After Saturday February 2nd, the pattern is expected to soften and arctic air will retreat somewhat. Will this retreat provide an opportunity for another thaw in the first full week of February ? Possibly a short one, but I haven't seen anything too disconcerting as of yet and we will need the pattern to soften, at least somewhat, to open the door for storminess.