CHICAGO -- Another day of scattered heavy thunderstorms inside what forecasters called a juicy, "tropical-like" air mass Saturday has renewed the risk of flash flooding across several states from Iowa to Pennsylvania, including Chicago and the outskirts of Pittsburgh.
The storms are firing along a nearly-stationary front draped along the border of a massive heat dome that has been cooking much of the nation this week. The heat dome shrunk Saturday to mostly focusing its triple-digit warming powers on the coastal Southeast and mid-Atlantic, but thunderstorms riding along the edge of the dome are tapping into an unstable and exceedingly moist atmosphere.
While the risk of severe weather is low, rainfall rates of up to 2 inches per hour are possible in the stronger thunderstorms that may stall or train over the same area.
Similar storms wreaked havoc in south Chicago on Friday, where a cluster of thunderstorms brought 4-6 inches of rain in just a few hours. Roads and underpasses turned into instant rivers and lakes, requiring multiple water rescues across the southern suburbs. The previous heavy rains have also saturated the ground, leaving the area more susceptible to flash flooding with lower rainfall amounts.
CHICAGO SLAMMED WITH FLASH FLOODING AFTER 5 INCHES OF RAIN FALL IN FEW HOURS
NOAA's Weather Prediction Center has issued a Level 2 out of 4 threat for flash flooding along much of the stationary front stretching from northern Missouri and southern Iowa, through northern Illinois and Indiana, and even into western Ohio. That includes the Chicagoland area.
A second area of flooding concern Saturday covers a swath of western Pennsylvania, including the eastern Pittsburgh outskirts.
So far, Flood Watches are in effect for northern Iowa into Chicago and northern Illinois.
An unstable atmosphere, mixed in with heat and a moist air mass, is a budding recipe for possibly severe weather in the eastern mid-Atlantic.
NOAA's Storm Prediction Center now has a Level 2 risk out of 5 for severe weather covering the Baltimore and Washington, D.C. area. Damaging wind gusts of 60 mph or more are the main concern.
The heavy rain chances will shift into the mid-Atlantic and Northeast on Sunday, but flash flooding risks will wane. New York, Philadelphia, and Washington, D.C. will be a few of the cities that will be dealing with afternoon thunderstorms, but so far, NOAA only has low-end risks for any flooding or severe weather.
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