The Summer Severe Weather Pattern Is Changing

We continue to find ourselves in a very active severe weather pattern, with cold fronts sweeping through the country every few days and bringing another round of thunderstorms, damaging winds, hail, and heavy rainfall.

And today is no exception.

Another cold front will move through the Ohio Valley and Appalachians, bringing the threat for severe thunderstorms across parts of Ohio, Pennsylvania, West Virginia, and potentially into eastern Tennessee. Some of these storms could produce damaging wind gusts and large hail, while torrential rainfall could create localized flooding problems.

But while we've seen this kind of severe weather pattern repeatedly throughout the summer, something is beginning to change.

The Air Behind The Fronts Is Different

The interesting part of this pattern isn't necessarily the storms themselves. It's what is happening behind the cold fronts.

The air masses arriving behind these systems are beginning to look much more like fall air masses.

We're seeing lower dew points, cooler temperatures, and noticeably more comfortable air filtering southward behind the fronts. In fact, we're beginning to see some of the first overnight lows in the 50s across portions of the country.

That may not sound particularly unusual in late August, but it is significant because we haven't seen much of that type of air during the heart of summer.

It's a sign that we're beginning to break the back of summer.

The atmosphere is slowly transitioning.

September Is The Bridge To Fall

September has always been that transition month between summer and fall, and I think this year we're going to see that transition become increasingly obvious.

The cold fronts are going to continue coming through, but gradually the air behind them is going to become cooler and drier. The humidity won't be quite as relentless, and those stretches of comfortable weather behind the fronts will begin lasting longer.

That doesn't mean summer is suddenly over.

We'll still have warm and humid days. We'll still have thunderstorms. And we can certainly still see some hot weather during September.

But the overall character of the atmosphere is changing.

We're moving away from the peak of summer and toward the beginning of fall.

And Then There's The El Niño

This is where things get particularly interesting.

As we move into fall, the developing El Niño is expected to continue strengthening. Eventually, we're going to see the jet stream begin responding to that changing Pacific pattern.

And once that jet starts dipping farther south, that's when I think things could get really interesting.

A stronger southern jet can bring increased moisture and storm activity across the southern United States while creating a much more active storm track across the country.

If the colder air begins building across the northern part of the country at the same time, we're going to have a tremendous temperature contrast between the cold air to the north and the warm, moist air to the south.

That's when you can start getting some really significant storms.

Hang On, Folks

We've got a long way to go before winter, and there are still plenty of unknowns regarding exactly how this El Niño is going to evolve.

But the atmosphere is already giving us hints that we're entering a major transition.

The severe weather pattern isn't going away yet. In fact, we'll continue to see these cold fronts and thunderstorms coming through during the next several weeks.

But now we're starting to see something different behind those fronts.

The air is getting cooler.

The dew points are dropping.

The nights are getting longer.

And we're beginning to see those first signs that fall is waiting just around the corner.

September will be our transition.

Then we'll watch what happens to the jet stream.

And if that jet starts digging south as the El Niño strengthens...

Hang on, folks.

I think we're in for a ride of a lifetime heading into the winter months.