After Terrible Heat/Humidity Flood Threat Growing In Vermont/New England. Few Severe Storms Too?

The road to storminess. Photo of a thunderstorm looming
in the distance looking west/northwest from St. 
Albans, Vermont last evening. Showers and storms
are expected to become numerous today, with
some flash flood risk again. 

UPDATE 9 AM

The National Weather Service office in South Burlington has hoisted a flood watch for northern and central Vermont for today.

The watch covers everything from Addison and Orange counties northward, along with northeastern New York.

Confidence is growing that this afternoons showers and thunderstorms will be wicked enough to produce locally torrential rains. 

These rains could easily cause localized flash floods and flooding along streets in cities and towns. 

The flood watch goes from noon today to 10 p.m. tonight. 

PREVIOUS DISCUSSION

This might sound like a broken record, or crying wolf, but, the flood threat is once again growing in Vermont and much of the rest of New England. 

Starting today.  And coming back Sunday and Monday. The threat of flash flooding in Vermont is actually bigger than it has been in recent weeks.  We've only had isolated reports of flash flooding in Vermont in recent days. It's possible the problems could get more widespread between now and Monday.  

More on that in a  minute, but first, we can't ignore the heat and humidity we've been enduring.

I don't have exact figures to back it up, but in my opinion, yesterday and last night were arguably Vermont's worst combination of heat and humidity in a few years.  Perhaps hot spells in the Julys of 2020 and 2018 were comparable, but Thursday was unquestionably bad.      

Actual temperatures weren't really off the charts. The high temperature in Burlington was 93 degrees. We often get at least one day during the course of a summer that hot.  Montpelier didn't even make it to 90, topping out at just 89 degrees.

The humidity is what killed it.  Usually during hot days, the atmosphere mixes somewhat, drawing drier air from aloft down.  So at the peak of the day when it's in the 90s, the humidity goes down a little.

Not yesterday. In Burlington, the dew point stayed firmly near 70 degrees most of the day. That led to a heat index that peaked at 101 degrees. Ugh.

And it didn't cool down much in the evening and overnight like it usually does. The low temperature last night in Burlington appears to be 77 degrees.  Another yuck.

FLOOD/STORM RISK

With all that heat and humidity around, we are now primed for some locally dangerous storms today.  Flash flooding is the biggest risk,  though some storms could bring damaging winds and hail to a few spots. 

A few showers and storms were already rumbling through parts of New York early this morning. They'll strengthen and get wetter as they slowly crawl toward Vermont. 

The storms should reach the Champlain Valley late this morning or the first half of the afternoon. They'll move into the rest of the state during the afternoon and very early evening. 

There's just a TON of moisture available for these storms.  Which means some of them will be heavy rainers.  The storms will move pretty slowly, too, giving them time to drop a LOT of rain in a short period of time.

We also have another chance of those dreaded "training" storms, the series that go over the same spot on the map over and over again. 

Since soil moisture has gotten much higher in recent weeks, it's easier to set off some flash flooding now.  More than three inches of rain might come down in a few spots, especially in central Vermont, at least according to some of this morning's forecast.

This doesn't mean we're in for a widespread flood with havoc everywhere.  But urban and street flooding is possible. (NOAA's Weather Prediction Center based in College Park, Maryland specifically mentioned Burlington as a possible urban flood target today). 

Other parts of the state, especially in the central Green Mountains, could see road washouts or small brooks turning into torrents that could cause a fair amount of property damage.  That Weather Predication Center has us under a "slight risk" of excessive rain and flooding today, which means they expect scattered instances of flash flooding.

Do note that flash flood risk isn't just in central Vermont.  It could happen anywhere in the state today. You just can't predict exactly where until it's happening, or just about to happen. 

The other, lower threat today from the storms are strong, damaging wind gusts and hail.  The wind damage will be fairly isolated. I imagine just a few unlucky towns will see downed trees and power lines. 

There could also be a lot of lightning with these storms, so today's not the day to be out on the lake or hiking to mountain summits. 

BUT WAIT! THERE'S MORE!

The so-called cold front setting off today's storms will die a pitiful death over Vermont overnight, so the humidity will linger for sure. 

Saturday will be another day of scattered showers and storms, especially in eastern Vermont. Again there could be some heavy rainers. There could be an isolated instance of flash flooding on Saturday, but the risk is lower than today.  

But it ain't over. 

Forecasters are still worried about another slug of heavy rain coming in Sunday, Sunday night and Monday. This threatens to be a real troublemaker, with the potential for more widespread flooding across Vermont and elsewhere in the Northeast. 

The National Weather Service office in South Burlington is toying with the idea of issuing a flood watch for Sunday. They're wisely holding off, because they don't want to sow confusion with any weather warnings they have to issue for today's storms. Plus, there's still some questions on where the heaviest rain will set up later Sunday. 

The best guess for real flood trouble is over the eastern half of Vermont later Sunday and Monday. But I would emphasize there's still a LOT of questions about how much rain will fall and where. The flood risk is statewide late in the weekend and early next week. 

Today through Monday, make sure you have a way to receive weather warnings.  Especially if you're in a flood prone area or will be in such a location.  And please don't drive over flooded roads.