Thursday, August 11, 2016

Hot, Oppressive, Volatile, Potentially Dangerous New England Weather To Continue

Flash floods like this one in Montpelier, Vermont in
2011 could occur in Vermont and the rest of New England
this weekend. 
I cowered in my St. Albans, Vernont basement today.

No, there was not a tornado warning or any severe weather nearby.

But it was HOT, and my un-air conditioned home was torrid. So me, my husband and our dogs Jackson and Tonks huddled in the basement quietly. It was the only cool place in the house.

The high temperature in nearby Burlington, Vermont today was 96 degrees. That would normally be near record territory had not today been the anniversary of the hottest day on record in Burlington -- 101 in 1944.

Although storms did not drive me into my basement today, the hot air enveloping New England with heat indexes of over 100 in some places is contributing to some scattered dangerous storms. And will continue to do so over the next several days.

Although wind and hail are a threat, the biggest risk over the next few days is flooding, which is a switch from the drought or near-drought we've been in.

Yesterday, tornadoes touched down in North Haven, Connecticut and in eastern Long Island.

Around dawn this morning golf ball sized hail dented many cars and trashed crops around Caribou, Maine.

More strong storms erupted in Connecticut today.

Now, much of New England is in a drought, and most of the parts that aren't are damn close to it. In fact, part of the Merrimac Valley in northeastern Massachusetts has descended into severe drought.

So it seems strange that we're talking about the possibility of flooding, but there you go. Weather whiplash again. One extreme to another.

As mentioned previously, a weather front is going to sink slowly southward across New England over the next several days, and little storms will ripple along it.

That'll trigger lots of showers and thunderstorms. The heavy rains from some of this activity could produce flash floods. The risk is high enough so that the National Weather Service in South Burlington, Vermont has issued a flash flood watch for the northern two thirds of Vermont and northeastern New York Friday afternoon into Sunday.

You might be asking: What's the big deal? Doesn't is usually rain hard during a thunderstorm.

Well, yeah. But the air is so humid and the thunderstorms would have so much moisture to work with, that the rain could come down especially hard. Especially in highly localized terrain.

In fact, we're talking about near record amounts of available moisture in the air for August. This is brought to us by an "atmospheric river" of wet air from the Gulf of Mexico. Atmospheric rivers are especially dangerous when it comes to the threat of flash floods.

That's because it can cause a narrow band of thunderstorms to repeatedly go over the same area, dropping incredible amounts of rain

Another thing to consider: The ground is rock hard from the drought, and less able to absorb the water from torrential downpours. So more will run off into local streams, worsening the flood threat.

We're talking two to five inches, possibly in  jus ta few hours. That's more than enough to trigger a local flash flood anywhere in New England this weekend.

Most places won't have flooding. But those that do will have to watch out.

It seems the biggest threat is along the Canadian border Friday afternoon and evening, much of northern and central New England Saturday, and southern New England Sunday.

In general the rain will help ease the drought. But as noted, in spots, it will be too much of a good thing.

That means you should stay aware this weekend. No driving into flooded roads, please. No camping near stream banks, and if you must,  be ready to climb a hill at the drop of a hat.

Bigger rivers are running very, very low, so I don't think there will be flooding along those waterways. The water might rise in those rivers, but not enough to endanger roads, buildings and people.

If you still think we can't really get dangerous flash floods during dry summers, I will take you back to August, 1995 for a weather setup similar to this weekend's.

The summer of 1995, like this one, was hot and dry in Vermont. Then, Tropical Storm Dean made landfall in Texas. The weather pattern brought incredible amounts of wet air from Dean into Vermont, causing a very devastating flash flood in the Lamoille River Valley of Vermont.

This time, there's no tropical storm, but there is a weather disturbance along the Gulf Coast contributing to the atmospheric river of volatile wet air headed toward us.

These things are always uncertain. It might not be a big deal, and we'll just get some beneficial rains. But it could  be nasty, and there won't be much warning before any floods hit.

A few storms Friday in northern New England could be severe Friday afternoon and evening, with gusty winds and hail possible, but I don't expect a widespread severe outbreak.

It's not going to be 96 degrees anytime soon in Vermont, but it will remain very humid into Sunday in the Green Mountain State, and the rest of New England for that matter.

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