Thursday evening weather update: Flooding and severe weather possible

Heavy rain threat increasing this evening and overnight across Northern Illinois - especially tied closer to the warm/stationary front.
 
Technical discussion from the Weather Prediction Center:
SUMMARY...ADDITIONAL HEAVY SHOWERS AND THUNDERSTORMS WILL PRODUCE
LOCALLY VERY HEAVY RAINFALL OVER THE NEXT SEVERAL HOURS. FLASH
FLOODING IS POSSIBLE.

DISCUSSION...LATE-DAY 1-MIN GOES-14 SRSO IMAGERY SHOWS AN
ORGANIZING AXIS OF HEAVY SHOWERS AND THUNDERSTORMS DEVELOPING
ALONG AND OUT AHEAD OF AN AREA OF LOW PRESSURE MOVING EAST ALONG
THE IA/MO BORDER. THIS LOW PRESSURE WAVE IS ASSOCIATED WITH A
WELL-DEFINED SHORTWAVE TROUGH THAT IS MOVING INTO THE
MIDWEST...AND OVER THE NEXT SEVERAL HOURS...CONVECTION IS EXPECTED
TO INCREASE IN COVERAGE AS THE SHORTWAVE ENERGY INTERACTS WITH AN
ENHANCING POOL OF RELATIVELY DEEP MOISTURE AND INSTABILITY.

HI RES MODEL OUTPUT INCLUDING THE 12Z ARW/NMMB AND 22Z HRRR
FORECAST AN INCREASE IN THE S/SWLY LOW LEVEL JET OVER THE NEXT FEW
HOURS...AND THIS WILL ENHANCE THE THERMODYNAMIC ENVIRONMENT FOR
CONVECTION TO EXPAND IN COVERAGE AND INTENSIFY. THE LATEST
GOES-SOUNDER IMAGERY ALREADY DEPICTS A POOL OF 1.5 TO 1.75 INCH
PWATS ACROSS MUCH OF THE LOWER MO VALLEY WHICH WILL ENHANCE THE
RAINFALL RATES. MEANWHILE...THE LOW TO MID LEVEL STEERING FLOW IS
FORECAST TO BECOME ORIENTED MORE PARALLEL TO THE FRONT...WHICH IS
EXPECTED TO ENHANCE THE POTENTIAL FOR TRAINING CONVECTION.
THEREFORE...SOME VERY HEAVY RAINFALL TOTALS ARE EXPECTED WITH SOME
AMOUNTS POTENTIALLY EXCEEDING 5 INCHES THROUGH LATE EVENING. THIS
COUPLED WITH SOME OF THE RECENT HEAVY RAINFALL SEEN SHOULD ENHANCE
THE THREAT FOR FLASH FLOODING.




5:50pm Update: A Tornado Watch has been issued for Lee and Whiteside counties until Midnight.  Storms developing south of the Quad Cities are forming along a warm front, feeding off the instability south of the front and wind shear with changing winds near the front.  Earlier, the storm south of Davenport did have a Tornado Warning with.

The greatest storm threat appears to be south of Rockford.  However, as the evening progresses and the low level jet increases, the threat for severe weather could shift a little further north.

A Flash Flood Watch has been issued for all of Northern Illinois through Friday morning in anticipation of the rainfall later today and tonight.   

We've got a little break from this morning's rainfall, which produced over an inch of rain in far NW Illinois, but additional showers and thunderstorms are moving through eastern Iowa.  We will remain dry for the next couple of hours, but heavy rain producing thunderstorms will build across Illinois through the late afternoon and evening.  This rain will fall on an already saturated ground increasing the threat for flash flooding.