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| Once again, my yard in St. Albans, Vermont was a winter wonderland this morning. About 1.3 inches new when photo taken, still snowing (7:00 a.m.) |
One such storm scooted by New England yesterday morning, but the main driver of the lousy, unseasonable snow we're having is what is for this time of year an amazingly large and deep pool of cold air high above us.
That cold air up there is extensive (though it's now beginning to wane)
At very roughly 5,000 feet above the Earth's surface, it was below freezing from Minnesota through New England and on into eastern Canada. That cold area extended all the way down into northern Alabama.
No wonder there were wide areas of frost and freeze warnings and advisories in the Ohio Valley and Mid-Atlantic states early this morning. And no wonder it was a frigid 18 degrees atop Whiteface Mountain, New York at one point yesterday.
This upper level cold air is a symptom of a storm in the upper levels of the atmosphere, and sure enough, there was one pretty much centered in New England Thursday. Usually storms at the surface are centered to the east or southeast of the upper low and that was the case yesterday. (It was near Nova Scotia early this morning.
The sun angle this time of year is high, so when the sun filters through the clouds when it's that cold aloft, pockets of warmish air rise, form clouds and showers. Yesterday, here in Vermont, those were mainly in the form of snow showers.
It was cold enough aloft to chill the snowflakes that some of them made it to the ground in the Champlain Valley Thursday afternoon while temperatures were in the low 40s. By late afternoon, some of the snow showers were briefly heavy-ish and began to accuumulate.
Overnight, the snow in Vermont came down in earnest. Of couse, unlike during the day, the snow had no help from the sun causing rising pockets of air.
Instead moisture pinwheeling from offshore Canada around the surface storm up there and the upper level low high above brought wet air down from Canada on to us. The moisture would rise up the western slopes of the Green Mountains, where it was wrung out as snow.
My place in St. Albans is where land begins to rise in elevation east of Lake Champlain. as of 6 a.m. I'd received about an inch of snow, and it was stil coming down at a good clip. I'm sure we'll get reports of several inches or a half a foot or even more closer to the Green Mountain summits.
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| At roughly 5,000 feet above sea level, it was below freezing yesterday in the blue area inside the black line |
The snow today will keep getting spottier and spottier and more confined to the mountains. A few raindrops will come down in the valleys.
The upper levels of the atmosphere are still cold today, so we won't be able to warm up too much today. The April sun, though strong, can only do so much when it's that cold aloft, and when there's clouds around.
But the atmosphere will warm, and day by day, you'll see improvements. As noted in previous posts, Saturday will also be chilly, but at least there will be some sun. Sunday will be cool for this time of year, but not bad. Temperatures near 50 will be easy to take after all the cold and snow over the past week or more
We're still looking at 50s and 60s Monday and Tuesday. The next storm arrives late next week. We're still not sure how big or small this next one will be, but it surely looks like it will be too warm for snow with that one.
For those who like heat, here's a ray of hope for you. Admittedly, long range forecasts looking out several weeks or months are not known for their pinpoint accuracy, but a long range prediction by the National Weather Service issued yesterday calls for generally warmer than normal temperatures in the Northeast during May, June and July.
On the other hand, European models suggest we might have a cool May.
We'll see
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