More storms! Increase in “thunderstorm potential” days over past 40 years

Climate Central says we’re getting 5-10 more unstable days than in 1979

Increase in stormy days since 1979, per Climate Central (Copyright 2022 by WSLS 10 - All rights reserved.)

ROANOKE, Va. – It’s not a shock (no pun intended) to hear that thunderstorms are in the forecast in Southwest and Central Virginia during the warmer days of spring and summer.

However, Climate Central tells us the number of stormy days could be increasing, due to an increase in convective available potential energy (CAPE).

First, let’s talk about what it takes for a thunderstorm to form. There are three ingredients we look for: instability/fuel (CAPE), a lifting mechanism and moisture.

Thunderstorm ingredients (Copyright 2022 by WSLS 10 - All rights reserved.)

Moisture is self-explanatory. You need more humid air to tap into for the big clouds and heavy downpours in thunderstorms.

A lifting mechanism can be a cold front, an upper-level low, an outflow boundary or even just air lifting up our mountains.

The instability/fuel component is what Climate Central looked into. They say that we’re getting 5-10 more days per year with a CAPE value of at least 1,000 J/kg since 1979. That number is a benchmark that meteorologists look for when forecasting thunderstorms.

Increase in stormy days since 1979, per Climate Central (Copyright 2022 by WSLS 10 - All rights reserved.)

If you look closely at the map, you see that the change in high CAPE days is more pronounced in the Piedmont versus the western mountains.

It stands to reason that if you’re increasing the number of days with one of the three thunderstorm ingredients, you’re getting more days with storms in general.

The next round of thunderstorms in our region is expected to arrive Wednesday night. Meteorologist Chris Michaels is tracking them in our daily forecast article.


About the Author:

Justin McKee presents the weather forecast on 10 News Saturday and Sunday mornings from 6 to 8 a.m. He also fills in for other meteorologists during the week.