Severe Thunderstorms Could Overshadow Heat On First Day Of Long Hot Spell

NOAA's Storm Prediction Center says they'll likely issue
 a severe thunderstorm watch for the area outlined in blue.
Still, a layer of warm air might prevent the storms from
forming this evening. It's nearly a 50-50 proposition.

UPDATE 6 PM SATURDAY:

As of this evening, it's a battle over whether a disturbance coming in from the northwest will be enough to trigger storms, or will a layer of stable air in the atmosphere prevent those anticipated storms from forming?

I think it will be one or the other and not some muddled middle ground in northern Vermont and the rest of the North Country this evening.

Either the layer of stable air wins out, preventing the kind of updrafts that lead to big storms, or anything widespread for that matter, or the weather disturbance coming in will erase that stable layer, and storms will develop explosively from there.

I doubt we'll have just middling light showers out of this.

Some widely scattered storms did pop up today in northern New York, northern Vermont, the upper tip of New Hampshire and southern Quebec. They all died out very quickly, though some became briefly strong. That indicates the potential for bad storms is there, but the stable layer in the atmosphere prevented the storms from really getting going. We have to get rid of the stable air to really get a bad outbreak this evening

One strong thunderstorm has developed late this afternoon east of Ottawa, Canada, but as of 5:30 p.m. I don't see anything widespread developing yet. However, NOAA's Storm Prediction Center remains fairly bullish on big storm development in southeastern Canada in the next couple of hours.

The Storm Prediction Center has given themselves a 60 percent chance they'll soon issue a severe thunderstorm watch for northern New York, northern Vermont, northern New Hampshire and western Maine soon. The time frame is pretty brief. I'd say if things get going, this region will be under the gun from about 7 p.m. to midnight. Then the storm threat will quickly wane.

Enhanced risk of severe storms (in orange) has popped up in northern
New England, says NOAA's Storm Prediction Center. A large area
in the center of the nation is also at risk.

Usually, when there's this little storm activity, I would abandon the idea that we'd get any severe storms. But when it's this hot, and this humid, and there's a pretty strong disturbance coming in to destabilize the atmosphere, I think differently.

If things develop this evening, it will be sudden. If it plays out as I think it might, weather radar might show pretty much nothing, as it does as of 5:30 p.m., then a half hour later, the radar lights up like a Christmas tree.

For what it's worth, the HRRR short term radar animation has a batch of strong thunderstorms plunging southward across Vermont and New Hampshire after dark this evening, with the strongest storms from the Green Mountains east.

The storms would then rapidly weaken over central Vermont and central New Hampshire. We'll see how that plays out.

Of course, that stable layer I talked about might just win out. If I don't see thunderstorms developing in southeastern Canada by 8:30 or 9 p.m. this evening, I'll just call it a missed forecast.

Until then, keep a close eye out on the hot, hazy skies in the North Country this evening. Just in case.

UPDATE: 1 PM SATURDAY:
The severe thunderstorm threat over northern areas of the region later today looks higher than it did this morning.

NOAA's Storm Prediction Center has upgraded the severe risk in the northern tip of New York, Vermont north of Route 2, northern New Hampshire and parts of western Maine to "Enhanced"

Enhanced risk is in the middle ground for the SPC's storm risk scale. It goes from marginal, to slight, then enhanced, then moderate, then high. So Enhanced Risk is nothing to sneeze at.

And frankly, I never trust the weather pattern we're in today. It's a somewhat unusual pattern, but one that often spells trouble for northern New England in particular when it sets up.

The heat and humidity we're in now provides fuel for strong or severe thunderstorms. High overhead, the air flow is coming in fast from the west-northwest. Little disturbances are embedded in that air flow. When the upper wind are from the west-northwest like this, that tends to favor the development of severe storms, and those little disturbances trigger the storms.

The biggest risk from today's storms continue to be damaging straight line winds. Of special concern is the possibility of something called a bowing echo. That's a term for a line of strong storm arrange in a line that resembles a backwards "C". At the apex of the backward "C" winds get particularly strong, and widespread damage often occurs at this point along the path of a bowing echo.

One or more bowing echoes are possible late this afternoon and evening. Also, given the fast wind flow aloft, the thunderstorms can "grab" those strong winds and bring them to the surface.

Again, not everybody in the Enhanced Risk zone will have damaging thunderstorms. It will be hit or miss, with some towns or neighborhoods being blasted, but most areas in the zone will have little or no damage from the storms. It's luck of the draw.

There's a very low, but not zero chance of a tornado or two in the Enhanced Risk zone. If a thunderstorm can get to rotating, you could get at least a brief spin up.

Despite the high humidity we're experiencing on the Earth's surface, there's also a dry layer way up there. That encourages the formation of hail, so a few gardeners in the North Country are at risk of having their tomatoes and hostas shredded. Again, not everyone will see that, but a few of us will.

PREVIOUS DISCUSSION:

Lots to talk about today. Heat here. Heat over there, in the UK. Heat in Colorado. Severe storms possible here. Severe storms in a lot of other places. Let's get going:

STEAMY, STORMY SATURDAY IN VERMONT:

Although we know a heat wave is beginning today, the sky early this morning over northern Vermont did not scream "hot spell."

I looked up roiling clouds,  and a breeze was keeping the air feeling pretty reasonable out there.

This was largely because we're on the edge of the massive high pressure area that is creating the heat baking the eastern half of the nation.

Along the edges of hot high pressure systems like this, you get clusters of storms, those MCSs that I described yesterday.
One such MCS early this morning caused severe weather in Ontario, Canada early today We were close enough to the thunderstorm complex that clouds were washing over us.
These type of storm clusters usually weaken after dawn and before the heating of the day really takes hold. The Ontario storms headed toward northern New York and Vermont, but washed out on their way there. At most, northwest Vermont might get a sprinkle before noon, if that. 
The sun is coming out at least partially, and the heat should take hold this afternoon. So will the humidity. You will get uncomfortable if you're outdoors later this morning and especially this afternoon.

Remember, though, we're close to the edge of the heat wave. During the day, the sun's heating helps create more thunderstorm clusters, and we're under the gun later this afternoon and this evening. Especially in northern Vermont.

It's hard to say if storms later today will arrive in one concentrated cluster or be more scattered in nature. But during hot spells, any thunderstorm can develop explosively and quickly become severe.

I'm almost positive that there will be some reports of wind damage and/or large hail over southern Quebec, northern New York, northern Vermont and maybe into New Hampshire.

Obviously, not everyone will get a severe storm with damaging winds, but a few towns will get nailed. As always, it's hit or miss. If you live in northern Vermont especially, you might just get a rumble of thunder and a light shower, or you might get some decent lightning, wind gusts and a heavy downpour, or, in a few cases, some of your trees will blow over.

The clouds this morning and the storm threat this afternoon might keep some areas in northern Vermont and New York below 90 degrees, but most of us should get there.

HEAT WAVE OUTLOOK

As has been said over and over all week, tomorrow and Monday look to be the worst days, with temperatures of near 90 degree weather probably continuing for most of the upcoming week. This will mean we'll experience one of the longest stretches of Vermont heat on record.

Remember, heat waves become more and more dangerous for people the longer they last. A week of 90 degree days, with oppresive warm, humid nights, wear people down, and those with pre-existing health issues are really at risk. If you know anybody like that - anyone who is frail or elderly, make sure they get air conditioning breaks.

Take them to the movies, or the mall, or anywhere that has some air conditioning blasting. Some towns here in the North Country are setting up cooling centers where people can go and hang out in air conditioned rooms.

As if the heat were not enough, there's always the risk of a strong afternoon or evening thunderstorm during hot spells like this. Most of us won't get 'em, but a few of us might, starting Tuesday and continuing daily through Friday.

It's looking more and more like a glorious cold front will come through sometimes Friday night or Saturday. If this happens the way we think and hope, we'll be back down to normal temperatures next weekend. A high temperature of "only" 80 degrees sounds awesome, huh?

OTHER U.S. HEAT

The heat built near the eastern slopes of the Rockies this week and is spreading east. Denver, Colorado on Thursday tied its all time record high temperature of 105 degrees. 

No doubt other heat records will be set in the eastern half of the nation during the week. This won't be the worst heat wave on record for the nation as a whole, but it will be a doozy. An unusually huge area of nation is under heat advisories and warnings.

By the way, heat is not a photogenic disaster like tornadoes, but torrid conditions are one of the most deadly weather hazards. About 150 to 300 people die directly as a result of heat in the United States each year.

Basically the heat alert zones run from Oklahoma to New Hampshire and Wisconsin to North Carolina. Those of us that will be complaining about the heat in Vermont have a lot of company elsewhere in the nation. And overseas. 

Record heat melted the tar on this Irish road this week.

UK HEAT 

The United Kingdom - including England, Scotland and Ireland - are experiencing some of the hottest weather on record there. 

It was so hot in Glasgow, Scotland that the membrane of the roof of a science center melted. At 89 degrees, it was the hottest day on record in Glasgow.

Belfast, Northern Ireland also had its all time record high this week, with a reading of 85 degrees. Tar on some roads in England and Ireland melted.

SEVERE STORMS:

It's not just Vermont under threat for severe storms. On Thursday, three separate, large thunderstorm complexes hit different areas of the United States. One batch of storms dropped at least five tornadoes on western South Dakota.

Another bunch of storms cut power to tens of thousands of people around St. Louis, Missouri. Some people there are still without power as temperatures threaten to climb to near 100 degrees.

Yet more storms swept the Southeast as a derecho swept through.

So, everyone, enjoy the heat and the storms.