Did you know that heat waves can cause nocturnal thunderstorms?

AccuWeather

Severe storms in the Great Lakes area and extreme heat in the Plains this week are actually directly related. AccuWeather's Bernie Rayno breaks down how that connection works.

Transcript

00:00 The threat for nocturnal storms increases this week in parts of the country.

00:04 These are thunderstorms that happen after the sun goes down, which can make them even

00:07 more dangerous.

00:08 Bernie Rayno takes a closer look.

00:10 Well, in our weather-wise segment tonight, we're talking about nocturnal thunderstorms.

00:15 It's a fascinating process.

00:18 Unfortunately, it produces lots of weather, damaging winds and also flash flooding.

00:22 We saw that during the overnight period last night across Michigan and Ohio.

00:27 We're going to get it again tonight, and it always occurs on the northern side of heat.

00:32 It depends where your upper-level high is located.

00:34 Now, the last 24 hours, that high has been across Oklahoma.

00:39 What happens is you build the heat, you build the heat all afternoon hours, and then that

00:44 heat is transported on the northern side of high pressure northward.

00:49 Then that heat continues to come northward, and then when it intersects where you have

00:53 northwesterly flow aloft, that's where the showers and thunderstorms occur, because what's

00:58 happening?

00:59 That northwesterly flow aloft is bringing cool air down.

01:02 So, warm at the surface, cold air aloft, same situation you get during the afternoon when

01:07 you get the heating of the sun, right?

01:09 It's just a different process.

01:10 Now, here's how it works.

01:12 Typically, we don't get these thunderstorms in the afternoon.

01:14 You know why?

01:15 Because the sun's out, it's warming the cloud tops or warming the upper atmosphere, and

01:20 you don't have a big enough temperature difference between the surface and aloft to get the instability

01:24 to produce the thunderstorms.

01:26 But then what happens at night?

01:27 You lose the sun, you continue to bring that northwesterly flow down, right?

01:31 Bringing in the cool air aloft, you don't have the sun, you start cooling the upper

01:36 levels, but then here comes the heat that builds up during the day.

01:38 That makes for a very unstable environment, and then the showers and thunderstorms blossom.

01:43 They tend to peak after midnight.

01:46 But then what happens in the late morning?

01:48 Well, the sun comes out.

01:49 You start heating the cloud tops.

01:51 You start warming things.

01:52 You use that temperature difference, and then the clusters of showers and thunderstorms

01:56 dissipate.

01:57 That's the life of these nocturnal thunderstorms.

02:00 And as I mentioned, with all the heat that's trying to come northward and eastward across

02:04 Ohio and Pennsylvania, look for another cluster of thunderstorms late tonight across parts

02:09 of Pennsylvania and New York State.

02:11 [BLANK_AUDIO]

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