Friday Vermont Early Afternoon Update: "Locally Significant Flash Flooding" Possible in Southern Vermont This Afternoon, Evening

Forecasters are now saying "locally significant flash 
flooding" is possible this afternoon and evening
in parts of southern Vermont, along with much 
of New Hampshire and northern Massachusetts. 

UPDATE: 2:30 PM FRIDAY

Concern is rising in far southern Vermont for the risk of flash flooding this afternoon and evening.  

By 2:15 p.m, pockets of heavy rain and thunderstorms had already developed over the southern Green Mountains.

A large patch of drenching rain, meanwhile, was moving in from the west, beginning to affect most everything south of a Burlington to Newport line,

The part of this drenching patch of rain heading into southern Vermont should intensify as it hits humid, more unstable air there. 

Plus, more torrential thunderstorms should develop, mostly south of Route 4. 

Early this afternoon, NOAA's Weather Prediction Center, put out a statement warning of the risk of "locally significant flash flooding" in steep and hilly terrain of the southern Green Mountains,

This potential significant flash flooding extends into the Berkshires of Massachusetts and much of southern New Hampshire, especially the Monadnock Mountains. 

In these areas - again including the southern Green Mountains - local areas might see as much as three to five inches of rain of rain in just a few hours. Rainfall rates could briefly reach two inches per hour, which is a big indicator of a flash flood risk, 

The ground is also very wet already in southern Vermont, so it can't absorb all that much water.

Some flash flooding is possible as far north as central Vermont, but it won't be potentially as severe and widespread as in the south. 

Take this one serious, especially if you live in southern Vermont, the southern half of New Hampshire and the western half of Massachusetts. 

There were no flash flood warning in effect yet as of 2:30 p.m., but the worst of the rain hadn't arrived yet. The threat will peak between roughly at between roughly 3 to 8 p.m., but could linger beyond that.

If you live in an area prone to flash flooding, have a to-go bag ready now, and a planned route to escape.  Also, some of you in southern Vermont might be temporarily trapped behind washed out back roads, 

It's honestly too late to run out and get food and stuff in advance of any flooding. You don't want to be caught out on the roads, especially ones near small creeks and streams when the rain really hits. Those streams can go from placid brooks to roaring rapids sometimes within minutes.

Not every town in southern Vermont will see a flash flood. But it's time to be on your toes through the rest of the afternoon and evening. Just in case. 

 

PREVIOUS DISCUSSION FROM THIS MORNING

Once again, some localized flood risks have popped
up today. In Vermont, southeastern parts of the 
state especially have a chance of local but
to widespread flash flooding. 

Thunderstorms in Vermont were fewer and further between on Thursday than expected, though some of the some of the widely scattered storms eded up being pretty strong. 

We have no reports of any damage so far, so it doesn't look like any of the storms achieved severe status. 

A couple strong storms originated in or near Addison County and crossed over the Green Mountains to areas north White River Junction. I'm sure some of those towns along the way did experience a rambunctious storm. 

90 DEGREES

The relative lack of thunderstorms Thursday also meant more sun, allowing Burlington to achieve its first 90 degree day of the season. 

That was a day later than expected.  Some forecasts called for 90 degrees on Wednesday, but the city didn't quite make it, stopping at 88 degrees.  The mostly sunny skies that lasted until at least mid-afternoon Thursday let Burlington briefly sneak up to 90 degrees in the mid-afternoon. 

The first 90 of the season has been coming earlier in the season recently, compared to, say a generation ago. That's owing at least in part to climate change. The first 90 of the season on Thursday was earlier than historically common. But compared to the last 20 years, it was sort of so-so early.

In the past decade, four of Burlington's first 90 degree day of the season came at a later date than June 5.  In 2015, the first 90 didn't hit until July 28.

The earliest in the season first 90 came on April 17, 2002. Burlington has had a handful of years, like 1998, 2000 and 2004 with no 90 degree days at all. 

TODAY'S STORMS

We're going to have two very different Vermonts today and tonight. Southern Vermont will be stormy and wet. With even a risk of some flooding and severe storms.

Northern areas, not so much, though a little rain should creep in. Right near the Canadian border it might not rain at all, or it does, it won't amount to much.

Which means all eyes are on southern Vermont.  Yesterday's weak cold front stalled and has become a warm front, which will drift ever so slowly into central parts of the state.

South of the warm front, the air is humid and unstable, which suggest lots of showers and thunderstorms. Especially this afternoon.

The principal threat is local flash floods. There's a level one marginal risk of flash flooding in central and southern Vermont, with a somewhat more substantial level 2 slight risk of flash floods in extreme southeast Vermont. (And in western Massachusetts and the southern half of New Hampshire.)

A few spots in southeast Vermont could see two to as much as three inches of rain in a short amount of time this afternoon, which suggests flash flooding is a possibility there.  It won't be widespread, but a few places are at risk.

I'd say the steep terrain of the eastern slopes of the extreme southern Green Mountains, and the lowlands just to the east where the water will flow has the best shot of flash flooding. 

I'd keep an eye on Whetstone Brook in and near Brattleboro today, and nearby streams, just to be on the safe side. No guarantees of flooding there, but if you've got stuff that can be easily moved away from the brook or those surrounding streams, do it this morning, just in case. 

There's no flood watch currently in Vermont, but flood watches are in effect immediately adjacent to the Green Mountain State in Massachusetts and New Hampshire. 

Another secondary problem in far southern Vermont is severe storms. A few could contain strong damaging winds, maybe a couple of microbursts. Nothing at all like Austin, Texas had on May 28, but a couple towns in far southern parts of the state could suffer some localized tree and power line damage. 

A level one marginal risk of severe storms, meaning isolated damaging winds at most, is in effect for areas along and south Route 4. As of early this morning, level 2 slight risk is up for central New England, just barely creeping into southeastern Vermont around Brattleboro and Guilford.  

SATURDAY

Believe it or not, Saturday is looking....OK. At least in the afternoon and evening. I'm not holding my breath, given our recently history, but at least some of us might enjoy some sun as the afternoon wears on and evening approaches.

At least it won't be a complete washout like last Saturday was. 

Southern Vermont will still have the worst weather in the state, just as they will today. It'll be a rainy morning, as Saturdays in Vermont now seem to be required to have rain. But skies should brighten by mid to late afternoon. Except maybe in far southeast Vermont, where it could remain cloudy all day. 

The further north you go, the less rain and the less chance of rain you'll see.  In fact, it's possible parts of Vermont close to the Canadian border might break the sacred Saturday "rule" and see no rain at all!

Bottom line. If you have outdoor plans Saturday in Vermont, the later in the day they start, they better off you'll be,

The only fly in the ointment later in the afternoon is a secondary cold front will come through. That could touch off a few isolated showers and storms, but nothing widespread at all.

SUNDAY

Another miracle might hit Sunday.  At least some of us in Vermont should end up with a Chamber of Commerce kind of day. You know, perfect for the tourists. After a comfortable night for sleeping overnight Saturday, Sunday's highs should reach the mid 70s, at least in the valleys. The humidity should stay nice and low. 

 Places away from the mountains should have mostly sunny skies, with just some puffy clouds around over the mountains, to make the photos and background for your selfies that much prettier. 

There will probably be still some Canadian wildfire smoke in the atmosphere, so the sky might not be a brilliant deep blue on Sunday. The blue might have that bit of a slate gray tint to it because of that smoke. I guess not everything can be perfect. Still, the smoke shouldn't be as thick as it was earlier this week, and I don't anticipate anything serious enough to prompt air quality alerts. 

If you're in the mountains, the skies could get a little cluttered with those puffy clouds in the afternoon, so the sun won't be consistent there. But it will still be nice. No rain!