Snow To End Later This Morning; Clouds, Chill To Linger

Managed to shovel part of my driveway in St. Albans,
Vermont before work this morning.  Will finish
after short work day this afternoon. Easy job, as
it's only two or three inches and it's not wet or heavy.

As of 8 a.m., this Christmas Eve morning, we're almost done with our latest bout of snow, but road conditions remain tricky, as you can imagine with snow still falling.  

Radar images at 8 a.m. showed the back edge of the snow just crossing the Canadian border into northwest Vermont, so most places will be done with this by midmorning. 

The National Weather Service in South Burlington will probably drop the winter weather advisories and winter storm warning, also by midmorning. 

Best early guess is most of the forecasted amounts of snow will come to fruition, except maybe in the Champlain Valley  

Both upper level winds from the southwest and strong surface winds from the south up the Champlain Valley cut back on snow accumulations. 

The southwest winds a few thousand feet up meant the Adirondacks of New York blocked some of the moisture from getting into the valley. 

Winds on the ground gusted to around 40 mph at times, stronger than forecast. That created a lot of blowing snow, but messing up whatever snow was falling. The blasting gusts smashed snowflakes apart, causing smaller fragments to all, which don't accumulate as readily as regular, intact snowflakes.

The winds were diminishing as we approached sunrise, so most of the snow in the Champlain Valley will have fallen at the end of the storm.  Still, I imagine places like Burlington and Middlebury might end up with only one to three inches of new snow.

Eh, those places got some Lake Champlain-effect snow Saturday, so they're OK. 

 It was hard to measure how much snow I got at my place in St. Albans, Vermont because the snow blew around quite a bit overnight. Good measuring spots ranged rom 2.5 to 3.2 inches of new snow around my yard.

Northern New York appears to be the big winner of this system, with a couple of 7 inch reports coming in from there. So far reports from Vermont are sparse. Preliminary reports include 6.7 inches in Albany, Vermont, 6.5 inches in Morrisville 5.3 inches in Cabot and 4.1 in Topsham.  

OUTLOOK

As expected, road conditions were iffy for what amounted to this morning's commute. Traffic cams showed snow or slush covered highways statewide.  

Screen grab of traffic cam on Interstate 89 near Exit 16 in
Colchester shows not great conditions. If you have
holiday travel today, probably best to postpone
the start until late morning or afternoon. 

This should improve pretty fast later this morning and afternoon.  Temperatures should either stay in or get into the 20s by this afternoon, so not terrible.

Although strong high pressure is moving in, we might not see a huge amount of sun during the day, or starlight at night, especially in the valleys. 

That inversion we've been talking about will set up.  An inversion is when it's warmer a few thousand feet overhead than it is down in the valleys, which is the opposite of how the atmosphere is usually set up. 

An inversion traps a layer of moisture a couple thousand feet up, which means you often see a low, dull overcast in the valleys with this type of thing. Especially this time of year, when the sun's low angle isn't powerful enough to mix the atmosphere and clear out the clouds. 

Pollution can get trapped beneath the inversion layer, too, so we'll have to watch and see what air quality does Christmas through Friday. 

If you venture up to the ski resorts, you might be treated to an undercast, rather than an overcast. That cloud layer could end up below you, so if you're up on the mountain, you might be in bright sunshine while a layer of clouds spread out below you. 

After today, the next chance of any kind of storminess looks like it might come along about Sunday. By then it will be warmer, so at this point, it looks like that stuff might end up being rain, with possible areas of freezing rain.

Ah, yes, the joys of a Vermont winter!