Saturday, July 20, 2019

Heat Wave Peaks Today; Iffy Forecast For Storms And Rain

Yesterday's heat and humidity made the lower atmosphere unstable
over St. Albans, Vermont last evening, resulting in these pretty clouds.
Storms did not develop because there was another warm layer above,
which prevented the strong updrafts you need for storms
So we got these nice little clouds instead.
The heat wave that has engulfed Vermont and most of the rest of the nation's eastern half should peak today, then slowly begin to wane in most places

It's a doozy, even if not that many records are being set. There will be a few record highs, but what's striking is the warm overnight lows. Several cities will set a record today for the highest minimum temperature for the date. 

Burlington, Vermont did manage to get down to 72 degrees this morning, which is hot, but not unprecedented. It'll get into the 90s today in Vermont, with heat indexes approaching 100 degrees.

Needless to say, we're still under a heat advisory.

It's worse elsewhere, of course. I don't think it got below 80 degree last night in Boston, for instance. 
There's a chance it could reach 100 degrees in Boston today or Sunday. If it does make it to 100 in Boston, it'll be something like only the 25th time in 140 plus years of record keeping.

Cities like New York and Washington have a good shot at cracking 100 degrees today.  People are wisely cancelling strenuous outdoor events, which can give people heat stroke. In New York City, for instance, a triathlon is off the table for today, as is something called OZY Fest, which would have drawn big, eclectic names like John Legend, Trevor Noah, Rachael Ray and Beto O'Rourke.

Some events in Vermont are canceled or postponed due to the heat, too. Ironically, this heat wave is a bit like a blizzard in that it's cancelling events.

It is good though that strenuous things are being put off. This heat is dangerous. Among the people succumbing to heat stroke yesterday was former NFL player Mitch Petrus, who died while working outside his Arkansas shop on Friday.

Here in Vermont, as hot as it is, I doubt we will have a record high temperature. On this date in 1977 there was a super impressive heat wave that brought temperatures up to 99 degrees in Burlington. It won't get that hot today.

Still, be careful! The humidity is way up there, so heat indexes will be up around 100 degrees, as I've already noted.

It's still unclear whether thunderstorms will help break the heat, even when a cold front comes into play on Sunday. Often, heat and humidity ends with an outbreak of frequent thunderstorms, but not always.

This appears to be the case. Depending on whether anything can get triggered, some thunderstorms could erupt this afternoon and evening. I don't think they'll be particularly widespread, but given the rich environment, any that do get going could get pretty strong pretty fast.

We still have that layer of warm air which would block updrafts, but a weak boundary coming through today might provide just enough lift in the atmosphere to trigger a storm or two.

It is a bit unpredictable when you're on the northern edge of a heat wave, like we are now.  Big complexes of storms or derechos can form. One derecho or severe storm complex has gotten going early this morning in South Dakota and is beginning to race eastward. Even if it aims towards us late tonight, I imagine it will weaken greatly before it gets here. Still, it's worth watching.

The Storm Prediction Center has us in a marginal risk zone for severe storms today and tonight.

Even as the cold front comes through Sunday, the storms will be hit and miss. Not everyone will get 'em. It will remain hot and humid Sunday, especially in southern Vermont, which will be the last to see the cold front.  You'll start to notice the fresher air in the evening across the north, and statewide overnight Sunday night.

The front will get hung up in southern New England Monday, and a little storm will ripple along it. That would bring rains to parts of the area Monday and Tuesday. Nobody is quite sure yet where the front will stall, which means nobody knows where the heaviest rain might fall. There is a chance that parts of Vermont could get some pretty heavy downpours Monday and/or the first half of Tuesday.

It's still looking nice and cool next week, though as we get toward Friday it might start to warm up again. But not to the extent we're dealing with now.

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