A Wet Spell Coming To Vermont: Some Risk Of Flash Flooding; Far North Might Miss Out

National Weather Service forecast map. Through Thursday
morning. If this forecast holds, the southern half of 
Vermont would get more than an inch of rain, with
local amounts much higher. Northern Vermont 
looks like it will get less. 

Today is dawning as it did the past couple of days, sunny, a little hazy from atmospheric wildfire smoke in the air.  

According to WCAX meteorologist Gunnar Consul said that Sunday was the exact midpoint between Burlington's average last and spring snowfall. So, we're in the midsummer doldrums. 

Which means slow moving, sluggish weather systems. 

For most of us, today will be a relatively nice day. But if you were a geek watching weather radar yesterday, you saw some slow moving showers and thunderstorms in the Adirondacks. There's not much motion of the atmosphere so they kind of sat there. 

The same state of affairs will happen today, and that introduces a rainy stretch that will lead to the risk of some localized flooding over the next few days. I'm absolutely not in panic mode like I was before  the big summer floods of 2023 and 2024. 

This episode doesn't look nearly as dire as that, unless there's some incredible surprise all the meteorologists are missing. But be on the lookout for the risk of some local flash flood problems that might erupt between today and Thursday.  

TODAY

The local flash flood risk starts today, almost exclusively in the Adirondacks. And maybe the western side of Lake Champlain in New York. That said, the chances of that happening are low. I just mentioned it because storms that develop won't move much. So they could dump huge amounts of rain in very small, pinpoint areas. That can be dangerous within the steep slopes of the Adirondacks.  

Here in Vermont, we'll watch the storms erupt here and there to our west, on the other side of Lake Champlain. Eventually, later this afternoon and early evening, a few showers or storms will erupt in Vermont, too. Most of us will stay dry and enjoy a nice day. Maybe 30 percent of us will get some rain by sunset. 

Because storms will be few and far between, it will get well into the 80s again today. 

TUESDAY

A much better chance of showers and thunderstorms, at least in the western half of the area. The disturbance causing the showery weather will have moved only slightly east. 

So there's an excellent chance of rain in southwest Vermont and New York. Much of central Vermont and the Champlain Valley has a very good chance of showers and storms. Again, since all the showers and storm will be moving very slowly, and some will contain torrential downpours.  All but the far Northeast Kingdom is under a marginal, level one of four risk of local flash floods. 

Northeastern Vermont should get through the day with just widely scattered showers and storms, so there risk os lover there. 

Again, this won't be a widespread problem. Since there will be sunshine, too, most of us should get into the low and mid 80s. The humidity will have risen somewhat, too. So it will be a partly cloudy, hazy, muggy day with the ever-present chance of showers and storms especially south and west of Interstate 89

WEDNESDAY

This will be the day with the best chance of rain. A nearly stalled weak but very wet storm will wander somewhere around New England and New York. This will set up a wet flow of air from the southeast - off the Atlantic Ocean - will push into New England, including Vermont. The heaviest rain will fall in southern Vermont, especially along the eastern slopes of the Green Mountains. 

We'll have to watch whichever spots ended up with the heaviest rainstorms on Tuesday will have to be watched for local flash floods. All but far northern Vermont is once again in a marginal, level one out of four on the risk scale. Areas in far southern Vermont - along Route 9 - are in a level 2 slight risk zone, as is most of southern New England. 

Areas in far northern Vermont that really need the rain look like they might miss out. It will rain up there. Any rain is good, but as it looks now, it probably won't be a deep soaker. 

Rainfall will be highly variable as it always is with showers and thunderstorms. In general, current forecasts give southern Vermont an inch or two of rain, with generally an inch in central Vermont. Far northern Vermont looks to receive only a half inch or so. Nice, but not enough.

Overall, with all the clouds and rain, it will be cool, but humid, with temperatures hovering in the 70s

THURSDAY AND BEYOND

Lingering showers and rumbles of thunder as that slow, rambling storm slowly leaves. So it will be an unsettled, iffy day. Some showers might linger into Friday. But warm, rather sunny, kind of humid weather will linger Friday and Saturday. Another sluggish system looks like it might arrive Sunday with more showers and storms. 

Debby Set To Cause Florida/Southeast Disaster; Lots of Questions Remain About Forecast Here In Vermont

Tropical Storm Debby had "that look" on satellite photos
this morning that suggested it wants to intensify
pretty fast before making landfall in northwestern
Florida sometime on Monday. 

 Yesterday's Wannabe Debby near Cuba is this morning's strengthening Tropical Storm Debby in the Gulf of Mexico about 150 miles west of Tampa. 

I decided to wait until late this morning to post, so I could get the most updated information on the tropical storm.  Debby's top sustained winds had increased to 65 mph by late this morning. It's getting close to becoming a hurricane. 

Debby is taking full advantage of extremely warm waters in the eastern Gulf of Mexico so that it is getting stronger pretty quickly and will be a hurricane when it makes landfall in what is known as Florida's Big Bend on Monday. 

That Big Bend is the area in northwest Florida where the peninsula bends and transitions to the Florida panhandle.

Anyway, the forecast looks very sure on its path to that landfall, and there's even a chance it could be a Category 2 hurricane at landfall. (That would mean sustained winds of at least 96 mph). 

After that, forecasters have serious questions as to what Debby will do next, but significant to maybe catastrophic flooding  (here we go again!) is likely somewhere in the Southeast.

Meanwhile, up here in Vermont, we have our own forecasts questions, unrelated, at least for now to Tropical Storm Debby. More on that further down.

DEBBY

This is becoming an unpleasant trend.  Climate change and other factors have led to record  or near record high water temperatures in most of the areas where hurricanes form and grow. This is jet fuel for hurricanes, and we keep seeing hurricanes become monsters as a result.

That's why Hurricane Beryl earlier this summer managed to become a Category 5 beast in the Caribbean. It's why Hurricane Michael back in 2018 was able to slam into roughly the same spot in Florida  as a Category 5 calamity that Debby will hit. The hot water is one major reason why we had so many other intense hurricanes in recent years.     

The saving grace with Debby is it won't have all that much time over water where it can strengthen. It only has about 24 hours to do so. But a lot can change in a day, so we'll really have to watch the intensity of this thing.

Debby already had those sustained winds of 65 mph late this morning, as mentioned.As you can see in the visible satellite photo of Debby this morning it has "that look" that suggests it really wants to turn powerful. The inner core of the storm still wasn't completely well organized as of early this morning. How fast that core gets its act together will determine how strong it gets. 

One rather ominous sign is that Debby was showing signs of forming a central eye late this morning, indicating that its organizational skills are pretty good. 

In any event, Florida's Big Bend can expect damaging winds, a ferocious, destructive storm surge and torrential rains.  The storm surge could be made bigger by two factors: Debby's overall size is pretty big, which means it can push more water into a storm surge. Also, that bend in the coastline along that part of Florida can compress incoming water from the left and right, causing higher surges.

That's why mandatory evacuations are ongoing today in areas near where Debby will make landfall.

That torrential rain will become the main, worrisome feature of Debby in the coming days. 

Uncertain Path, Big Rain Dump

The trough of low pressure in the upper atmosphere that is steering Debby toward Florida's Big Bend is dissipating and moving on, which will leave very little to push Debby in any particular direction after it makes landfall. 

When hurricanes make landfall, their strong winds quickly collapse into much lighter breezes. But these systems generate torrential rainfall for days after landfall. That's part of the reason we had a destructive flood here in Vermont back on July 10-11.  The remnants of Hurricane Beryl, which had made landfall in Texas days earlier, was able to contribute torrential downpours to a stalled weather front over Vermont. 

One problem is we don't know if the center of Debby will linger inland over the Southeast, or manage to  make its way just off the coast of Georgia or South Carolina. Either way, destructive flooding from inland downpours is inevitable. But if Debby goes off the coast, it'll have a chance to re-strengthen before moving back inland. 

No matter what happens, Debby is going to be a big problem in the Southeast starting today and going right through the week. 

In fact, due in part to Debby, more than enough rain to cause flooding is a decent bet at various times from now through next weekend anywhere from Florida to Maine. Which leads us to talk about Vermont. 

Spoiler: It's not dire, but we do have to watch the weather.

VERMONT FORECAST

The humidity grinds on. We are now on Day 6 in a row at Burlington in which the temperature failed to dip below 70 degrees. Saturday was the 14th day this year in Burlington which made it to 90 degrees. That's a tie for seventh most in a year. 

The Lake Champlain lake temperature was bath water this morning - 82 degrees which has to be a record high. 

We have 24 hours of oppressive humidity left in Vermont before the long awaited big change comes. Maybe a little more than 24 hours south. But it's coming. 

Until then, we have the ever-present risk of torrential showers and thunderstorms. They're always a risk in this kind of weather. 

Seems like every thunderstorm makes you worry, because we're spooked by the twin flash floods of July, and the other floods we endured last year. 

One storm popped up near Bolton and Huntington last evening that lingered for a bit. But luckily, it moved on and weakened just before it could cause major trouble.  I noticed a flood advisory for a corner of far southwestern Vermont early this morning, and locally  heavy rain was going on in spots in far southern parts of the state as of mid-morning.

More hit and miss storms are a good bet this afternoon and evening. Once again, many places won't see anything. Other places will get a quick drenching but otherwise not a big deal. But isolated places once again face the risk of microbursts, which would cause small pockets of wind damage, and isolated flash floods. 

NOAA's Storm Prediction Center has us at a marginal risk (level one of five) of severe storms today. Southern Vermont is under a marginal risk (level one of four) of flash flooding today. I think northern Vermont has a very low, but not zero chance of one or two flash floods. NOT a panic moment, for sure. 

Monday

The risk of severe storms and flash flooding will rise somewhat in Vermont as that long-awaited cold front comes in. It'll arrive early enough north of Route 2 to suggest the risk of severe storms is very, very low. We are under a marginal risk of flash flooding in all but far southern Vermont due to some downpours expected along the front.  

But in central and southern Vermont, there is the risk of severe storms. Morning sunshine will increase instability before the cold front pushes in, so we'll have time to see scattered severe storms to develop. Those areas are under level 2 risk of severe storms. 

Although rain might linger into the evening, we're still expecting the start of the longest period of coolish, low humidity days we've seen in quite some time.  Tuesday through Thursday look great, though some minor questions in the forecast mean there's a non-zero chance of light showers Tuesday, and maybe Thursday. 

Beyond that, we have HUGE question marks. During our break from the oppressive weather, that deep heat and moisture will be lurking not too far to our south.  It could surge back northwards at least briefly toward the end of the week. Plus nobody has any idea what Debby or its remnants might do. 

So stay tuned on that.  

Soupy Air, Likely Heat Advisories And Local Flood Risks Through Tuesday In Vermont

Here's an interesting visible satellite photo taken shortly
after 5:30 p.m Thursday. The white blob in southwestern
Vermont is a severe thunderstorm. Severe storm clouds
tower up to 40,000 feet in the air. So you can see 
the dark areas in southeastern Vermont and northwestern
Massachusetts. Those areas were in the shadow of these
very tall storms. 

UPDATE 3:30 p.m. Friday.

I anticipated this, and now it's official. Heat Advisory in effect for parts of Vermont over the weekend. 

It's a long lasting one, starting at 1 p.m. Saturday and going to 8 p.m. Sunday.

I think the National Weather Service is letting it go that long since Saturday night won't offer all that much relief. Many of us will stay in the humid low 70s at night. 

As far as torrential rain and flash flood chances, they're nil for the rest of the day and night in northern Vermont as that boundary of sorts has made it in, shutting off storms. 

There's a few isolated storms forming in the southern half of Vermont, and it's still possible one or two could be heavy rainers.

Only isolated storms are in the forecast Saturday, but one or two spots could get deluged. Again, it will be isolated.

There's a slightly better chance of storms Sunday with the best chance of heavy rain still looking like Monday and Monday night

PREVIOUS DISCUSSION

As expected, the air turned soupy as hell in Vermont yesterday, and we're stuck with this sticky air into Monday.

The incredibly high humidity for this time of year sets the stage for torrential downpours here and there. until more refreshing air finds its way to northern New England. 

It's classic flash flood weather, but I don't want to sound too alarming.  It just means that in some slow moving showers and storms in this weather regime, you can really pile up a lot of rain fast.  Few of us will actually see real trouble from this.  But there's a chance of local flash flooding into early next week. 

You can tell the risk is still quite low because I don't see any flash flood watches or alerts for anywhere around Vermont. But the risk is not zero. 

Just by walking outside, you can tell if there's the right trigger, the rain will come down in buckets. 

 When I walked out into my yard last evening, it really felt like air you could wear. You could actually kind of see the air.

It's only a slight exaggeration to say that I wasn't sure whether I was walking across my yard or swimming across it.  

Yesterday, clouds helped prevent both torrential thunderstorms and dangerous heat from building across the northern half of Vermont. But it southern Vermont, it got torrid, and the reward for that heat was some hefty thunderstorms, some of which carried warnings of damaging winds and such. 

The storm was particularly ferocious in the southwestern of Vermont, with lots of trees and wires down, some blocking roads, in Pawlet, Arlington and Bennington.  We have reports of similar damage in southeastern Vermont, around Newfane, Jamaica and Rockingham. 

These storms also dumped a good inch or more of rain easily in less than an hour. If those areas get additional torrential rains today, there could be some water issues there. 

More storms developed in the humid air this morning.  Residents around Hinesburg and Huntington awoke early this morning to quite a lightning barrage.  This storm dumped up to 1.5 inches of rain in a short period of time in parts of Chittenden County. The National Weather Service in South Burlington said the downpours fell just short of them needing to issue any flood advisories. However, they are watching this area in case they receive more buckets of rain later today.    

The root of all this potential trouble with water is a sluggish atmosphere and weather fronts lining up the "wrong" way. 

Most of the time, cold fronts that pass through Vermont are oriented in a generally north to south arrangement, while the air flow pushing the front is more or less west to east.

Which means that if that cold front can manage to create heavy rains, it won't last long in any one spot. The cold front will zip on through, and drier, rain-free air is hot on its tail. 

With the current weather set up, cold fronts or just weak nothing burger boundaries are kind of oriented west to east. So is the general air flow. So these fronts press southward only very slowly. Meanwhile, showers and storms move along the front or just ahead of it, west to east. That's the training I've been talking about. Storms repeatedly go over the same spot, and you get tons of rain.

Especially if the air just ahead of these fronts or boundaries is super humid. Which is what we're dealing with now. 

Then there's this added bonus. Around this time of year, the jet stream often retreats well north into Canada. 'Which means there's nothing to hurry anything along. So if thunderstorms form in the humid air, they don't move very fast. They dump a lot of rain in the same spot

On top of all that, there's something called backbuilding. Here's how that works: Say you have a mountain that creates a strong enough updraft to set off a thunderstorm.  That storm starts to move on to the east, but the updraft continues, so the storm keeps redeveloping over that same mountain, over and over until you get inches of rain.

There's no telling whether any of these scenarios will develop over the next few days anywhere in Vermont, but there's that low, but not zero risk that it could.

 Some of the heaviest ones today, especially if a particular spot gets several downpours in a row, could produce some ponding on the roads. There's a weak excuse for a weather front around Vermont now, oriented west to east, with showers moving along it.   As I write this early today, more downpours were lined up in New York, ready to come across Lake Champlain and hit north central Vermont again. Just like the earlier downpour. 

The weather front wannabe is is slowly sagging southward across Vermont while dissipating, so downpours will probably get more scattered, especially north.  So, I have a feeling this morning's downpours will begin to wane a bit, especially north.

Also, you might get some gullywashers, damage to the side of gravel roads or driveways, that sort of thing. Nothing widespread, though.  

In the hot, humid air that will be over us all weekend, there won't be much there to trigger thunderstorms. So they will probably be few and far between both days. 

However, isolated, slow moving storms could form in the updrafts in the mountains, which could unleash more torrents of rain in just one or two spots. In any event, take it easy this weekend. The combination of heat and humidity will make vigorous outdoor activity rather dangerous. 

Another front, a "real" cold front, looks like it will slowly shift north to south across Vermont early in the week.  Again, the flow will be parallel to the front, so that means we could get those "training" storms again, one after another over the same spots. 

We'll need to wait until we get closer to the beginning of the week to see how that all shakes out.