Saturday Evening Vermont Storm Update: Real Changes To Forecast

The start of the storm this afternoon in St. Albans, Vermont.
As snow came down, temperatures were below zero, making
salt ineffective on roads Things got slick fast. 

As expected, light snow moved into Vermont during the afternoon, to mark the start of our big winter storm.

As expected, we have some surprises in the storm forecast. This morning I said they would be surprises, so you shouldn't be surprised. Did you follow that? Probably not, but oh well.

The big changes are that there will likely be somewhat more snow than earlier forecast in northern areas of Vermont and New York.  

In southern Vermont, especially Bennington and Windham counties, there will be less snow than earlier forecast, because sleet will mix in.

I alluded to that sleet possibility this morning, and all the forecast trends this afternoon pointed more and more in that sleet direction. These ice pellets could work their way as far north as a Rutland to White River Junction line Sunday  morning.

THE CHANGES: FIRST NORTH

This is really an odd storm. I have to quote the forecast discussion from the National Weather Service in 'South Burlington. "Rather amazing snow event under way across the North Country."

The new Saturday evening storm forecas map. It's now saying everyshere
in Vermont should get at least a foot of snow, except the far south
Expected accumlations in northern New York are up substantially.

Here's why: Arctic air from Quebec has been feeding easily into the northern Vermont and northern New York.

Temperatures fell all day and were as low as -4 in Burlington and -8 in Highgate by mid-afternoon.  Dewpoints were in the 20 to 30 below range from Montreal north, which indicates pure Arctic air

This bitter air continues to drain southward into northern areas on a north wind. This situation is very often death to snow storms.

Arctic air is very dry, and helps evaporate snow before it even falls and hits the ground.  That's largely why initial forecasts called for only five inches of snow or so in New York's St. Lawrence Valley.  

Not this time. Despite the Arctic air that normally helps push storms further south, this storm is actually going to track a little north of earlier forecasts. On top of that, warm air is going to be able to ride north over the cold air more efficiently than first thought.

Which means snow totals in the north will be a little higher than first anticipated.  Now it looks like more than a foot will accumulate in the northern Champlain Valley all the way to and past the Canadian border. The winter weather advisory was upgraded to a winter storm warning in the St. Lawrence Valley of New York because instead of five inches, they will likely get eight to 12 inches of snow.

We also need to look out for more surprises in the north. It's possible a band of heavier snow that I said might set up in southern Vermont could set up in central or even northern Vermont instead.  If that happens, somebody, somewhere north of Route 4 could get two feet of snow or even a little more than that out of this storm.

Very cold air like this makes snowflakes small. Basically tiny needles. This type of snow is denser and harder to shovel than fluffy powdery stuff. Plus, it reduces visibility more than regular snowfalls.

Anticipate very poor visibility tonight and much of Sunday because of this. The snow will be more than powdery enough to blow and drift, so that's still going to be a factor.

CHANGES IN SOUTHERN VERMONT

The more northern track of the storm, and more powerful than expected push of warm air aloft, will combine to increase the chances for sleet to come down instead of snow. It'll snow hard at first in southern Vermont, then the chances for sleet ramp up Sunday morning.  .After that, any mix will go back to snow.

Because of the sleet, forecast accumulations have been cut back to about a foot south of Rutland and White River Junction, and as "little" as 10 inches or so around Bennington and Brattleboro.

For you winter storm enthusiasts, this isn't a disaster. The snow accumulation will be more dense than originally forecast, but it will be topped with a nice powder from the additional snow that will come down Sunday afternoon.

However, this will make the snow harder to shovel, because the sleet mixed in will make it heavier.

In the far south of Vermont, around Bennington, Wilmington and Brattleboro, it actually looks like there could easily be a period of freezing rain Sunday morning. I still don't think the freezing rain will last long enough to weigh down trees and power lines to the breaking point.

But the freezing rain will of course make life more difficult than expected in the southern end of Vermont. Road conditions will be even worse than earlier anticipated, and people will have to hack their way through the ice to get into their cars and such. I also have to wonder if emergency rooms will be busy from people falling on the ice.

SUNDAY AFTERNOON ONWARD

The forecast for Sunday afternoon and night is no different than earlier. The snow will come down at a lighter pace, but continue into Monday. Especially in the central and northern Green Mountains and downwind from Lake Champlain. These areas can expect one to as much as six additional inches of snow between late Sunday afternoon and Monday afternoon.

Although temperatures might "warm up" to the single digits above zero in northern Vermont for a time Sunday morning, readings will crash down below zero in the afternoon. Winds will pick up, and there will be a lot of blowing and drifting snow. Forecasters still expect dangerous wind chills through Monday at least.

After that, it will warm up starting Tuesday and continuing until near the end of the week, but there's still a lot of questions about how any storminess behaves from Wednesday onward.

ELSEWHERE:

Extensive tornado damage in Wetumpka, Alabama Saturday.

Because the storm has shifted northward, dangerous freezing rain is now expected in interior southern New England and coastal New Hampshire and Maine. Parts of New York between NYC and Albany are also under the gun.

These areas can expect some tree damage and power failures.

Snow and mixed precipitation will change to a heavy rain in the New York City area and southern coastal New England at least as far north as Boston. Flash flooding is possible in these areas. Also, coastal flooding is likely at the time of high tide Sunday morning.

The temperature will abruptly fall in these rainy areas Sunday afternoon, so a flash freeze will coat everything in ice.

Across the Deep South, the storm has caused an outbreak of severe storms and tornadoes. Social and local media are showing extensive tornado damage in Wetumpka, Alabama late this afternoon

I'll update this post as warranted this evening, and there will be of course other posts tomorrow. You can also get quick updates and little news flashed on Twitter, @mattalltradesb