Friday's Weather Was Bumpier Than Expected, Somewhat Less Wild Today

Looking north from Burlington early Friday afternoon at
some towering thunderstorm clouds that were over
Franklin County at the time. The haziness you see
is some rain falling nearby from another 
thunderstorm off a little to the west. 

 The thunderstorms that erupted Friday turned me into a bit of a liar.

If you read my post yesterday morning, I said there would probably be some thunderstorms around, but they wouldn't be particularly intense.  

For most of us, that turned out to be true. But the storms more numerous than I imagine.  

Worse, some of them were definitely on the strong side, borderline severe in some cases,  dumping heavy downpours that prompted at least one flood warning, hail up to the size of half dollars and a few wind gusts up to 40 mph or more.

The half dollar sized hail, 1.25 inches is diameter, was reported in the Addison County town of Waltham. Photos on social media also showed a patio in Vergennes covered with hail. 

For some reason, thunderstorms tended to repeatedly form near and just north of Plattsburgh, where hail to the size of quarters was reported.   

 Those New York storms occasionally made inroads into northwestern Vermont, where parts of Franklin County got hit pretty hard.  Penny sized hail was reported in Sheldon.  A flood warning was issued for the area around Sheldon, Berkshire, Franklin and Enosburg since the downpours lasted longer there than in other areas of the state.

I haven't seen any reports of serious flood damage, though

Here in St. Albans, I received two inches of rain from the downpours that hit Thursday evening combined with the thunderstorms that rumbled through Friday afternoon.  Although the thunderstorms diminished in the evening, some places continued to see heavy bursts of rain well into the night. 

I heard the roar of torrential rain on the roof a little after 11 p.m. last night. I checked the rain gauge and that was good for another 0.8 inches on top of the two inches we'd already received.

WHY IT HAPPENED

 It was essentially a second cold front that caused Friday's turbulent weather. The first one Thursday night flushed out most of the warmth and humidity, but not all of it. 

Meanwhile, an upper level low, which is essentially a pool of chilly air aloft, was moving toward us from Ontario. The leading edge of this cold pool formed into something of a new cold front. That, in turn created instability, in conjunction with the sun's heating, to produce the storms. 

Also, as that upper level low approached, the air aloft was cooling. That increased the contrast between the surface air and the air above. You could tell, as the downdrafts from Friday's thunderstorms from late morning to early afternoon pretty dramatically dropped temperatures as they passed through. 

Those downdrafts created gusts as high as 40 mph in a  couple spots. I noticed Burlington gusted to 33 mph as a nearby, dying thunderstorm exhaled a gust front through the city. 

The cold air aloft Friday also made it easier for the storms to manufacture hail, since a deep layer of the upper atmosphere was below freezing. 

TODAY AND BEYOND

That cold pool of air will be sitting nearly overhead today and Sunday.  That's already creating enough instability for some showers this morning, The strong June sun will heat the lower atmosphere despite the presence of quite a few clouds. The upper air is very chilly. The contrast will keep showers going and intensify them a bit by afternoon. 

There won't be anything quite as dramatic as Friday, but you'll still see some action. Some showers will contain rumbles of thunder and brief downpours. It's even easier for the storms to make hail today and Sunday, so I wouldn't be at all surprised if a few of the stronger showers produce pea sized hail.

It could rain at anytime now through Monday, but it won't rain constantly. The best chances of showers will be noon to 9 p.m., with the heating of the sun. If there's breaks in the clouds, at least the sky will be pretty, with those billowing, towering clouds around.

With the cold pool overhead, it'll be hard for even the intense June sun to warm us up much through the clouds. Highs should stay in 60s daily today through Monday. A few warmer valleys might sneak up into the lower 70s. 

The upper level cold pool will depart by midweek, allowing things to dry out and warm up a little. At least temporarily.

There are signs something else might come through late next week to maybe bring more rain, but it's too early to figure out if it will really rain then, and if so, how much.