Storms, Flood Threats Continue To Harass Vermont After We Hoped/Thought It Might Be Over

In a still taken from a video, a lightning flash around
midnight in St. Albans, Vermont last night briefly
turns night into day, 

 New storms fired up in and near Vermont yesterday and last night, not causing any harm, but harassing nonetheless.  

And, after we thought we might be done with the severe weather and flash flooding, a new threat of both has arisen for tomorrow. 

Yesterday's isolated storms followed a familiar pattern. They erupted, seemingly as they often do this summer, near Port Henry, New York and and again further north not far from Plattsburgh, New York. 

The Port Henry area storm yesterday did create some penny sized hail and knocked down a few branches. I was kind of intrigued by satellite images of the cirrus blowing off the top of that nearly stationary storm near Port Henry reaching as far as southern Quebec north of New Hampshire. 

The National Weather Service office in South Burlington kindly responded to an inquiry I made and said this summer has featured consistent southerly air flow up the Champlain Valley. The Adirondacks, especially near Port Henry and Plattsburgh help the air flow converge in those spots, leading to updrafts that create storms. 

Those storms then start to move over Lake Champlain toward Vermont, but tend to fall apart when they encounter the more stable air created by the comparatively cool waters of the lake. 

Last night, a little before midnight or so, a surprise thunderstorm strong enough to prompt a severe thunderstorm warning moved through Franklin County, Vermont.  Here in St. Albans, I didn't notice any strong winds, just a downpour and plenty of lightning. 

I suspect a temperature inversion might have deflected strong thunderstorm wind and prevented them from reaching the ground.  That storm put about 0.75 inches of rain in my unofficial rain gauge, but it was localized enough such that Burlington never saw a drop of rain last night. 

Today should be quiet, though it wouldn't surprise me if one of those areas in eastern New York between Lake Champlain and the Adirondacks pop an isolated storm today. 

THURSDAY

This is the new trouble day, though as of this writing, we don't quite know for sure whether we'll have renewed flash flooding or severe storms. Or, if they do occur, where they'll set up. 

Something called a mesoscale convective system, or MCS by weather geeks, was in Wisconsin and Minnesota this morning. It's basically a big cluster of thunderstorms and these things are common in the Midwest during the summer. 

More times than not, if they affect Vermont at all, these MSC's are going through a weakening trend by the time they make it here.

A familiar map rears its ugly head again. Best chances
for scattered instances of flash flooding tomorrow
appear to be in Vermont, at least according to 
this morning's forecasts. 

Not this one.  It's going to hold together nicely, and create a severe weather threat and/or a flash flood threat in New England, including Vermont tomorrow. 

Who gets what depends on the track and timing of the MCS.  A more northerly route opens the door to severe storms region wide, along with a flash flood risk. 

A slightly more southerly route would continue the risk of flash flooding all over the state, but would tend to keep the severe thunderstorms further south. 

If the best atmospheric dynamics with this come through in the afternoon, that would be the best timing for severe storms. 

 There's some hints that the arrival and departure of this thing might be a little earlier tomorrow than first thought, which might reduce the risk of severe weather and flooding somewhat.  But that's not a guarantee. Forecasts could change. 

Still, it looks like this could actually pose a low but real tornado risk again across southern and central New England, places like central and western Massachusetts and southern New Hampshire. 

All of New England has some threat of severe storms tomorrow, with the best chance, at least for now, south of a Rutland, Vermont to Portland, Maine line.  

As of this morning, the best chances of flash floods are focused - sigh - on Vermont. It'll be the drill we've become familiar with. Most people in Vermont will escape flash flooding but a few towns get nailed by washouts, road closures, that type of thing. Like we need any more localized damage.

Once again, expect some changes in this forecast between now and tomorrow. Of course, I'll update!

So the end to our flooding streak has been postponed. The next chance of any trouble would be with a cold front Friday night or Saturday, but so far the chances of flooding with that system look low.

After that, forecasters are still expecting an extended spell of cool and mostly dry weather starting later Saturday or Sunday and continuing into early next week.