Cold Snap To Be A Geeky Experiment, Anyway

Look closely and you can see the snowflakes coming down on my
St. Albans, Vermont gardens this morning. These poor flowers are
in for more snow and freezes over the next couple of days. 

While the cold and snow hitting the Great Lakes and Northeast this weekend is undoubtedly a huge bummer, I guess you can look at a rather dim bright side.

It's an experiment in a way for weather and garden geeks.

On Thursday evening, you could literally see the middle and upper atmosphere cooling over Vermont, if you knew what to look for. The sun had heated the surface to a temperature of near 60 degrees, just a tad cool for this time of year.

As the upper atmosphere cooled, some billowing clouds appeared. Warm air rises, especially if the air above is really cold. That forms those billowing clouds.

The air was quite dry last evening, , so it was difficult to form showers. But eventually, some rain came from one good sized cloud over St. Albans, Vermont where I live.

The air was dry enough so that the rain evaporated on the way down, so there was no precipitation where I stood.  But that evaporated rain cooled the air and helped bring the increasingly chilly air to the surface. Suddenly west winds from this "storm" gusted to about 30 mph and the air suddenly got dramatically chillier.

Web cam from this morning shows some snow on the ground
in high elevation Buels Gore, Vermont, along Route 17.

The cold spell was on, and it would only intensify overnight, and really get going tonight and Saturday, as forecasts have consistently indicated.

It briefly snowed this morning at my place, and I've seen photos of a dusting to a little over an inch of new snow in some high spots in Vermont this morning.

Another interesting thing to watch among weather geeks is what happens when a storm tonight gets going near New York City and intensifies as it moves along the southern New England coast and into the Gulf of Maine.

How much snow will the storm throw to its north and west?   It's hard to accumulate snow in May, but since much of the precipitation will be at night, there's no sunlight coming through the clouds to warm things up just a little.

Forecasts for snow in the central New England highlands, like the Berkshires, Monadnocks of New Hampshire, the far southern Green Mountains and the Catskills of New York have been cut back a little. Most of those areas are expected to get two inches or less of snow.

That wouldn't make it a historic May snow, but still impressive. Also, there's still room for surprises. That is, if the snow comes down harder than expected. We'll see.

Here in Vermont, from the Green Mountains eastward, a lot of places could get two or three inches of snow, especially in elevations of 1,000 feet or more. It's impressive that the National Weather Service is still calling for light accumulations of less than an inch all the way down to the floor of the Champlain Valley.

The huge expanse of dark blue in the middle of the nation on the
National Weather Service map this morning are freeze warnings.
That's an immense area to be under risk. Lighter blues are
mostly frost advisories. Note the winter weather advisory
in northern Maine. 

Another geeky thing to watch is how the snow showers play out Saturday afternoon and early evening. The atmosphere several thousand feet up will be at record cold levels for May.  The sun this time of year is strong, so that's a recipe for some real atmospheric instability.

Will that yield some gusty rain and snow showers, maybe even briefly heavy?

Don't be surprised to find a few heavy snow squalls, with new, brief snow accumulations. If you get a snow squall, you'll get a dusting to an inch of snow, which will likely quickly melt after the squall passes.

With these snow squalls, temperatures could get interesting.  "High" temperatures Saturday will be within a few degrees of 40, but snow squalls will briefly bring frigid air to the surface.  You could momentarily see temperatures drop to near 32 degrees in snow squalls, even in the valleys.

Whether and how many snow squalls form depends at least partly on the amount of cloud cover and the amount of sun that can sneak between the clouds.  In any event it's going to be a windy, raw day, much like you'd expect in early March.

For people who are into stats and climatology, it will be fun to see how many record lows are broken. A few cities in the Great Lakes and Midwest, and perhaps the Northeast, might experience all time record lows for May.

During the day Saturday, some record low high temperatures are in jeopardy, too, all the way from Maine to Texas.

Finally, there's the plant life out there. Not just here but in an immense area affected by the cold snap from South Dakota to Georgia to New York and New England. All these areas are under freeze warnings, or at least frost advisories.

Unfortunately, this cold snap has the potential for being a multi-million dollar disaster for orchardists and farmers in a huge area of the nation, especially east of the Mississippi and from the Carolinas north.

Here in Vermont, it will remain much colder than  normal through Thursday morning.  From Sunday onward, it won't be as cold as Saturday will be, but still far chillier than average for May.

And there's the freeze issues.  I had a bit of ice on the ground at my house earlier this morning in St. Albans, Vermont, followed by a snow shower.  There's a good chance or likelihood of frosts and freezes nightly through this coming Thursday morning. Here in St. Albans and elsewhere in Vermont, we could end up with seven consecutive mornings with readings of 32 or lower. In May!

At least it still looks like this won't last forever. Forecasts still call for a pattern change which would bring milder air in.  Definitely no promises on this one, but I did see one computer model with something interesting: Tomorrow, highs will be near 40 in Vermont. This forecast model calls for highs near 80 degrees exactly one week later.

I'm not buying that model, but it will be much better outside a week from now. I promise.