Monday, February 9, 2015

Quick Storm Update: Veers Away From North, Slams South

People in northern New York and northern Vermont are probably waking up this Monday morning, rejoicing or cursing the fact that it's not snowing, as expected.  
Somebody left their thoughs on a giant snowbank
in southern New England. But today, they're getting
plenty more snow. Not so much north, though. Add caption

Forecasts, including mine, for the north, were wrong.

The storminess affecting New England dipped a little more south than expected, and lots of dry air also invaded from Quebec. 

That shut off the northern snow. 

That dry air also contributed to a weird bit of freezing drizzle, which managed to fall on parts of New York and Vermont despite temperatures in the single digits. 

More on that in a bit.

So while snow-blasted southern New England is getting buried again, as expected, northern areas which have a fairly decent but not exceptionally deep snow cover, aren't getting much of anything. 

Winter storm warnings were dropped early this morning in northern New York and Vermont, and downgraded to advisories in central areas of those states. I think some of the warnings and advisories in the northern half of New Hampshire are going to bite the dust any minute, too.

Note that the winter alerts are gone, but the roads are still slippery. Already, as of 7:30 a.m., numerous car crashes have been reported in Vermont. 

As I mentioned, the storm is going, as expected to the south. North Weymouth, Mass. has already reported 19 inches of new snow, Norwell, 16.5 and several towns down there are up to around a foot.

It'll keep snowing all day in southern New England and some towns near Boston and Worcester could end up with two feet of new snow,

So, details on what happened in the north: All us forecasters knew northern areas would get less snow than the south, being further away from a stalled weather front south of New England that was contributing to the snow

The biggest burst of snow, due last night and today, would have been helped along by a final, stronger storm that was to have formed along the stalled front, then head east toward the New England coast.

That storm indeed formed and is definitely headed east toward the New England coast. It's just doing so a bit further south than expected.

We also knew there'd be a sharp line between snow and no snow, but the anticipation was that line would be over southern Quebec. 

Nope, try New York, Vermont and New Hampshire. 

The result was the example that happened at my house in St Albans, Vermont. The anticipated storm total was going to be seven to nine inches. Instead, I got a grand total of 3.3 inches. 

It's worth noting The Weather Channel picked up on this trend Sunday morning, and downgraded snow predictions for northern New England. The Weather Channel also predicted the relatively modest amounts of snow in New York City during the late January blizzard when everyone else was expecting something huge in the Big Apple.

The Weather Channel seems to be on a roll. I just wish they'd stop giving winter storms stupid names, even as I am impressed with their forecasting skills. 

FREEZING DRIZZLE AT 5 DEGREES?

Now, why was there freezing drizzle in  northern New York and Vermont yesterday and last evening even though it was so cold? I'm talking single digit temperature cold. 

It's a complicated explanation, but bear with me.

There was a layer of relatively low clouds over us yesterday that contained supercooled water droplets.  Believe it or not, water doesn't always freeze when the temperature is under 32 degrees. 

Water usually needs to come in contact with something cold, like your driveway or your windshield, to freeze. In the clouds, some tiny bits of ice crystals need to touch water droplets in the clouds to make snowflakes, which is basically ice, which then descend down on us.  

If there aren't any ice crystals to speak of, the supercooled water droplets in the clouds stay liquid. 
Remember that dry air I mentioned coming down from Quebec, which shut off our snow?  That dry air lacked ice crystals. Get it? It was dry. No moisture.

So instead of ice crystals falling into the somewhat lower level moisture to create snowflakes, some of the supercooled water in the lower clouds drifting toward  the ground came down as drizzle, which immediately froze on surfaces in the very cold air we had.

Bits of freezing drizzle and flurries should continue in northern New York and Vermont despite frigid temperatures today, so there is that to contend with.

AFTER TODAY

Despite the blown forecast for northern Vermont and New York, I'm still extremely confident we'll get a blast of frigid Arctic air throughout the region later Thursday and Friday, with a reinforcing shot Saturday night.  
The American computer forecasting models
are predicting a bitter Arctic outbreak
and a naty coastal storm for
New England this Thursday. 

I'm not sure if this will end up being record cold, like some computer forecasting models are suggesting for New England.  We might get that cold.

But at the very least, expect lots of subzero weather, possibly into the 20s and 30s below in northern New England during some nights during the upcoming cold wave. 

A lot of towns won't get above zero during the day on many days between Saturday and the middle of next week.

I'm less confident in forecasts for storminess. It looks like an Alberta Clipper will come through Wednesday and Thursday, then blow up into a big nor'easter off the New England coast. 

I know it will snow at least a little with this one throughout New England, but I'm not yet sure if the big nor'easter blowup will come close enough to the Boston area to give them another huge dump of snow.  Eastern New England ought to pay close attention to this one.

I'm also not sure how far north and west the heavy snow will get. 

Right now, I'm doubting anything more than a couple, maybe three inches will hit in most of New York, Vermont and northern New Hampshire. But, having said that, I was surprised today, so we could always get more surprises. Stay tuned. 

It's also possible a very frigid nor'easter could clip southern and eastern New England with even more snow on Sunday and Monday.  

Throughout New England, that storm could generate LOTS of wind throughout New England.  Combined with temperature way below zero, the wind chill could end up being the most brutal we've seen in years. 

No rest for the weary.

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