Tuesday, June 28, 2016

Severe Weather Threat In Vermont, Surrounding Areas Today

A severe thunderstorm looms over St. Albans Bay,
Vermont a couple summers ago. There's a good
chance of similar scenes today.  

Storms began firing up in northern New York state around noon, right on schedule and as of 1:30 p.m. were expanding and strengthening.

A few were poised to make it into Vermont within the next hour two, all the while getting bigger.

There will probably be only pockets of wind damage from the handful of severe storms that will develop within the oncoming area of occasional thunderstorms.

That's a typical pattern with Northeastern severe outbreaks. A few towns get hit hard, while most just get a regular old noisy thunderstorm.

NOAA's Storm Prediction Center issued a discussion of the situation at 1:09 EDT, and said they might or might not issue a severe thunderstorm watch for northern New York and western Vermont.

Wind flows are weak enough so that they're trying to decide whether there will be enough in the way of bad storms to warrant a severe thunderstorm watch.  Severe storms might end up being widely scattered at best. We'll see.

But these few severe ones can happen anywhere so watch out. Plus, the non-severe ones could still have a lot of lightning and gusty winds, so you'll still want to get inside.

It still looks like some of these storms might repeatedly hit a few areas of the hilly terrain of northeastern New York and most of Vermont, so local flash floods remain a threat throughout the day, despite the dry conditions we've seen this month.


I'd skip the hike or the boating excursion or the golf outing in Vermont today as we have a pretty damn good chance of some strong thunderstorms, which could turn severe in a few spots.

As I write this early Tuesday morning,  the sky is mostly clear over my weather hacienda in northwestern Vermont and the rest of the state.

Don't let that fool you. The sun will actually help create the storms that form today by adding heat and instability to the atmosphere.

A cold front is slowly coming in from the west and is pushing into the warm, humid air over us.

The timing is such that, according to NOAA's Storm Prediction Center, the area with the highest risk of severe storms is all of Vermont, eastern New York, northwestern New Jersey and eastern Pennsylvania.

Strong winds and local flash floods are the biggest hazards from these storms in Vermont and surrounding areas.

The National Weather Service in South Burlington sees a scenario in which storms will fire up in the Adirondacks around noon or a little after that, march into the Champlain Valley by mid afternoon, get into central Vermont during the late afternoon or evening and east of the Green Mountains later in the evening or early tonight.

As you can see, this line or area of storms will move pretty slowly. So it's going to be a pretty active day for a lot of us.

Don't go out on the lakes in Vermont today, or you
might find yourself under a scary sky like this. 
As is always the case with this type of situation, not everybody will get a severe storm. In fact most of us won't. But be on the lookout.

You should have a weather radio today with you, or failing that, pay attention to local media who will relay any warnings as to what to do.

Following are the kinds of weather alerts you might hear today, the relative liklihood of them happening and what to do about them.

Severe Thunderstorm Watch: Pretty damn likely this afternoon.  That means just keep doing what you were going to do anyway, with the following exceptions:

Keep an eye to the sky and listen for upgrades to warnings from the National Weather Service. (Details on what to do in the warnings are coming up a couple paragraphs down.)

This morning is an excellent time to get stuff that can easily blow around, like lawn furniture, toys, garbage bins etc. indoors so they don't become projectiles if storms really get going this afternoon. You don't want your neighbor to be clonked in the head with your beach umbrella or bouncy house, do you?
Todays Storm Prediction Center forecast map.
Areas in yellow have the strongest chance of
severe storms. Note that Vermont is yellow in this map.  

The likely thunderstorm watch also means, as noted, that you should ditch the plans for any major outdoor excursions today.

You don't want to be caught out in the middle of the lake when lightning strikes are slamming down all around you.

And jeez, Camels Hump has been there for a zillion years and will be for a zillion more. Can't you just wait for a nicer day to go on a hike up there?

I'd say there's a 99.99 percent chance of one or several or many gorgeous hiking days later this summer to take advantage of. Go then.

Besides, even if there are no big thunderstorms, do you really want to hike in this humidity, this wind, with haze and clouds ruining the view from the summits? Didn't think so.

Severe Thunderstorm Warning: Chances are pretty good but not certain you'll get one of these today here in Vermont

If you get a severe thunderstorm warning, get indoors. In a sturdy building.

It's tempting to look out at the storm through the windows, but that can be risky. Tthe biggest threats from today's storms are strong straight line winds that can cause damage, like blow out windows or send tree branches or other debris through them.

A secondary risk is big hail, but that is not as likely as the wind, but it's still something to consider.

Flash Flood Warning: Not all that likely, but possible in a few spots today and this evening.

I know what you're thinking. "Matt, you spent an entire weather blog post on Sunday whining about a drought in Vermont, and now you're telling me there might be a flood? Geez!"

Well, yes, it's been dry.

But here's the deal. As I said, these thunderstorms are going to be moving fairly slowly, because the cold front they're attached to is moving slowly.

This might mean thunderstorms could do something called training. They could line up like boxcars on a train track. Thunderstorm after thunderstorm would go over the same spot like all those boxcars, and each storm would drop heavy downpours.

The dry weather we've had means you'd probably need 1.5 or two inches of rain in an hour, or three inches of rain or more within three hours to set off a flash flood in Vermont today.

A few spots that get hit by one of these thunderstorm trains could get that amount of rain, which would send water gushing off Vermont's hillsides to form a local flash flood.

Any flash flooding would be limited to just a few spot areas. This isn't going to be a Hurricane Irene, which trashed the entire state with huge floods.

If you do get a flash flood warning and you're in a place that's high and doesn't flood, stay put. I know that's boring but read a damn book or something.

If you're driving and encounter a flooded road, for gawd's sake don't drive through it like so many idiots do. It doesn't take much water to at all to sweep a car away. And how do you know the road under the water is still there? It might have been washed away.

If your house is in a flood prone area, have a plan to get out very, very quickly. They call them flash floods for a reason. They happen in an, um, flash.

The weather in Vermont and surrounding areas will settle down tonight. For most of us, the storms today will be good thing, because we need the rain.

And it's fun to get a good old thunder bumper now and again.

Just stay safe.

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