Three H's of summer: Heat, humidity, and hail

Tomorrow could bring an outbreak of severe thunderstorms thanks to our soupy, unstable atmosphere. The Storm Prediction Center has placed us under a Slight Risk for Wednesday, but we're in a red zone that is almost-but-not-quite high enough for a Moderate Risk.

The Hazardous Weather Outlook from the NWS in Paducah explains that we have two chances for storms. First, a complex could arrive Wednesday morning, with heavy rain the greatest threat. Then "scattered to numerous thunderstorms" can be expected Wednesday afternoon as "extreme instability and increasingly strong wind shear will support a significant threat for severe storms with large hail and damaging winds."

It's possible that the storms during the morning could grow larger than expected, stablizing the atmosphere and putting the skids on the afternoon severe storm threat.

If they develop, the afternoon storms will be moving to the southeast, but individual cells have the potential to make a "right turn" and move to the south or even southwest.

The heat and humidity will provide plenty of fuel for the storms. One measurement of storm potential is called CAPE, or Convective Available Potential Energy. Charts from TwisterData.com show very high levels of CAPE for tomorrow afternoon:

According to the official forecast, the chance of storms tomorrow is 50%, so the NWS forecasters are hedging their bets that the event could be a dud. But if the storms do fire, the atmosphere will be primed for lots of ugliness.

Cooler weather on the way

Wednesday and Thursday could see heat indexes reach 100-105 before any thunderstorms arrive, but then temperatures should start to moderate on Friday. Indeed, we could actually start seeing below-average temperatures by Sunday and into next week.

The 8-14 day long-range forecasts is projecting cool weather:

This is a welcome change from last year's insane heat.

Severe weather webinar

The National Weather Service is hosting a webinar Thursday evening (June 27) featuring several speakers, including Chris Novy, a storm spotter who was injured in the recent El Reno, Oklahoma, tornado. See their website for details.