Thursday Night Severe Weather Event

 
 
 



(9:51:05 PM) nwsbot: Local Storm Report by NWS LOT: Kingston [Dekalb Co, IL] trained spotter reports FLOOD at 09:40 PM CDT -- glidden road south of hill road. 2 to 3 inches of standing water.




Just In:  Urban and Small Stream Flood Advisory for Northern DeKalb, Boone, McHenry, Northeastern Ogle, and Southeastern Winnebago County until 3:30am.  Doppler radar indicated heavy rain fell in that area due to thunderstorms, causing small stream and urban flooding.  Between two and three inches of rain has fallen in those area.

 

 

Picture of flooding from earlier today at the intersection of Rockton and Whitman.  Photo courtesy:  Kristen Kirk VanTassle

 

 

(8:25:46 PM) nwsbot: Local Storm Report by NWS DVN: NW Erie [Whiteside Co, IL] trained spotter reports HEAVY RAIN of E1.95 INCH at 08:00 PM CDT -- 1.95 rain total in less than 3 hours.

 

UPDATED 8:10PM

 

A Flash Flood Warning for Whiteside Co. is in effect until 11:30PM. Two inches and more of rain has already fallen over the past two hours. Flash Flooding is expected to begin shortly.

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Thursday evening brought some intense thunderstorms to the Stateline! Most of the activity we saw included periods of heavy rain and some high wind gusts.

One storm over SW Whiteside county was even put under a tornado warning after radar indicated broad rotation with the storm. That warning has since been cancelled due to the fact that the storm fell below severe limits. It was no longer capable of producing a tornado.

The atmosphere over the Stateline is much more stable than what is over central Illinois at this hour. CAPE (Convective Available Potential Energy - a measurement of atmospheric instability) in our area is below 500 joules per kilogram which is not enough to sustain a severe thunderstorm. This explains why the storm over Whiteside Co. weakened.

It is interesting to note how high shear values are over the Stateline (30-40kts). The change in direction and speed of the wind with height explains why the Whiteside Co. storm was able to rotate. Since instability in the region is not conducive for severe storms, we are not expecting shear or any parameter to encourage further severe weather development.

Bottom Line: Keep an eye out for heavy rain and gusty winds as we head for the overnight hours. These storms will diminish over the next few hours as the region gives way to nighttime cooling.