Saturday Evening Vermont Snow Forecast: A Quick Thumping, Then Lighter

The flat, gray light of pre-snow St. Albsns, Vermont at around
3:30 p.m. today That smooth, gray look to the sky was snow falling
from the clouds, but evaporating before reaching the ground.
The air had to moisten more beore snow started reaching the
ground a the first flurries of this storm at around 4:30 p.m. 

As of 4 p.m Saturday, snow was spreading southwest to northeast across Vermont, as expected.

For hard core weather geeks like myself, this has been kind of an interesting afternoon. The snow spreading in from the southwest has been encountering very dry air over us.

It has actually been snowing high overhead in Vermont since late this morning or early afternoon, depending upon where you've been in the Green Mountain State.

That's why the outdoor light today has been flat and gray and rather dark.  

The snow moving in earlier today fell into dry air and evaporated.

But that snow has moistened a layer of the atmosphere high overhead. More snow comes in, and it's able to get through that now-moistened high level air air, then encounters the lower level dry air, and evaporates.

The air gets wetter and wetter going from way up high to down low, until the entire mass of air above us allows snow to reach the ground.

You could see that in northern Vermont, looking at the Adirondacks and Green Mountains during the mid and late afternoon. The mountaintops got blurry, indicating the falling snow was reaching the summits before evaporating at lower elevations,

Gradually, the blurriness headed lower and lower down the slopes until the snowflakes arrive in the valleys.

This is one of those storms in which, when the air finally gets moist enough to support snow without evaporation, we basically go from 0 mph to 100 mph. Light snow develops, then quickly becomes heavy.

So, as we go through the rest of the late afternoon and evening, expect light snow to start, then, after a fairly brief period of not so impressive snowfall, it'll  get pretty heavy pretty fast.  Look for snow fall rates lasting a couple hours or a little more of one inch per hour. That's not record breaking, but pretty impressive.

As this snow keeps going from southwest to northeast over Vermont, there will be that embedded band of heavy snow. It'll make you think we're going to get more snow than forecast, it will be coming down that hard.

But nope, snow totals are still expected to be in the the three to eight inch range, with locally more in far southern Vermont and in the mountains of central and northern Vermont.

This expected band of heavy snow this evening won't last that long in any one place. After a few hours, it will have passed through.

In southern Vermont, forecasters have generally cut back on the amount of snow expected. Most of far southern Vermont was originally expected to get a good six to 10 inches of snow with higher amounts in some spots. Now, it's looking like around four or five inches or snow in valleys like around Bennington and Brattleboro, with eight or nine inches up high in places like Wilmington and Dover.

After midnight, the snow will be lighter, more showery and not that big a deal starting after midnight.  So basically, this isn't a huge storm, but the timing is lousy for people who had Saturday evening dinner or show reservations in Vermont.

All this heavier stuff coming through this evening is actually in advance of the storm. The storm center itself will pass by over northern Vermont or just north of there tomorrow.

That'll bring in a fast flow of air from the west.  That air will have some wetness to it, and will pick up some additional moisture from the Great Lakes.

That means during the day Sunday, it'll keep snowing in the western Adirondacks. The the air will flow up and over the Adirondacks and down into the Champlain Valley and valleys of western Vermont.

Sinking air, like the stuff that will be coming down the slopes of the Adirondacks Sunday, tends to dry out.  So the valleys of western Vermont won't see too much more snow Sunday. Just some occasional snow showers. If we get some extra instability in the atmosphere, snow showers in those valleys might briefly come down relatively hard, but not last long, so it won't be a big deal. Just a dusting. Maybe an inch or two in favored spots.

Then the air has to rise again, going up the western slopes of the Green Mountains. Rising air cools, and wrings moisture from the atmosphere as it does so. Which means forecasters still expect snow to continue much of Sunday on those western slopes and on the summits. That's great for the ski areas, right?

It's been a cold day, with highs mostly in the low teens. It'll warm into the 20s overnight, and get to the 25-32 degree range Sunday morning before starting to fall off again in the afternoon.

Monday and Tuesday, we're still expecting a  run-of-the-mill January chilly spell with highs in the teens and lows near zero.  Don't worry, you'll survive. This is normally, on average, the coldest point of winter. The expected weather early in the week isn't even remotely close to how cold it can really get this time of year. We've often had mornings in the 20s and 30s below in Vermont in mid and late January. Zero degrees is a heat wave compared to that.

Plus, we'll  turn mild again starting Wednesday and especially beyond that. The good news, if you like snow on the ground,  is this doesn't look like it will be some huge January thaw again. Highs will reach the 30s in the valleys, causing some minimal melting but nothing scary. Mountains should hold on to their new snow just fine.

No real storms are expected until next Saturday at the earliest, and frankly, even that looks iffy.