Friday, December 8, 2017

Let the December snowfest begin !!

Certainly a few rather important updates this morning and most of them are pretty darn positive as far as new snow is concerned in Vermont. So this Saturday storm is now "a thing" in the parlance of our current times. I need to be shamed somewhat for dismissing the possibility a few days ago. Models have such a difficult time dealing with fronts that so often linger around the Atlantic Coast. I've described the coastline as a "tinderbox" which it is, but a major consequence is that if models miss even slightly on one wave of jet energy, errors accumulate exponentially and 48 hours later the forecast picture is hardly recognizable. The wave of energy in question is causing snow in some rather unusual locations across Dixie. Its more of a disorganized but still rather significant conglomeration of moisture as of Friday but by Saturday it will have evolved into a garden variety coastal low pressure system. Snow will be falling across the Mid Atlantic and spread into southern New England during the morning hours.

The forecast picture for Vermont has changed profoundly as a result. We expected Saturday to be dry and quite possibly feature a good bit of sunshine. Though we may see the sun very early on Saturday, most of the day will be cloudy and snow should arrive by mid-afternoon. Across SE New England, this has become a very significant snow event and accumulations across a sliver of eastern Massachusetts could reach the 8-14 inch category. Snow will be on the lighter side across the Mad River Valley but still fall at a rather steady rate for several hours and total 3-6 inches by Sunday morning. The situation is still very fluid and models have been trending toward a stronger system and a farther west storm path. If this continues, accumulations would obviously be higher.

The storm Saturday will swallow much of the energy from the Midwest clipper we discussed a few days ago. That said, snow showers and even snow squalls are still likely on Sunday yielding some additional accumulations and leaving us feeling rather wintry as temperatures hover in the high 20's and then drop into the lower teens Sunday night. A weak area of high pressure will try and build across the region on Monday but flurries remain possible particularly in the morning.

I advertised "50 percent" or a "coin flip" on a big storm for Tuesday into Wednesday of next week. This probability looks closer to 80 percent as of Friday. Some disagreement persists relating to the track and timing of the event but the concept of a bombing New England/Gulf of Maine clipper system appears to be a universally accepted outcome. The clipper will spread its snow into Vermont Tuesday morning if all goes according to plan and the storm would strengthen. The disagreement mostly revolves around the track of the storm and would certainly impact overall snow accumulations and the positioning of dry air but not the overall forecast of snow. Accumulations could still wind in the modest 4-8 inch category if the American/Canadian model is correct in its assertion that the track of the storm is right over or even north of the state, but storm totals could reach a foot or more if the European solution is right and the storm path is closer to the southern New England coastline. Think we could probably iron out all those uncertainties within two days.

Bigger surge of cold weather arrives on Wednesday as the snow tapers to flurries. Though temperatures might be in the 20's Tuesday night, we should see readings in the teens for much of the day and drop into the single numbers by Thursday morning. There are some additional snow possibilities later in to the week and into the weekend for a variety of reasons. The pattern is then expected to relax somewhat on Sunday Dec 17th into the early part of the following week but the AO will remain a very dominant player on a continental level (negative AO) and cold air should remain available across New England even if temperatures modify substantially further south. A storm system is certainly possible in this time frame as the temperature gradient between the warm and cold intensifies.

We should see another good southward surge of cold weather just prior to the Christmas holiday weekend and I am ready to suggest that the 20-23rd of the month will be on the wintry side. Can we break this 6-year streak of a Christmas thaw. Certainly possible but those horses are not in the barn quite yet.

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