9:40pm Update: The Flood Advisory for Boone and Winnebago counties has been canceled. The heavy rain has ended in those counties and flooding is no longer a threat. There are additional showers that have developed south of Rockford and could see heavy rainfall with those.
Flood Advisory now issued for Boone County until 10:15pm. The storm that developed over Winnebago County has now slowly shifted east into Boone County, likely producing between one to two inches of rainfall.
8pm Update: The Urban and Small Stream Flood Advisory has been extended until 11:15pm. The heaviest rain core has shifted into Boone County with heavy rain occurring along IL 173 from Caledonia and Poplar Grove.
An Urban and Small Stream Flood Advisory has been issued for East-Central Winnebago County until 8:15pm. A nearly stationary rain shower near Machesney Park has produced close to one inch of rain within the past hour. Due to very light winds in the atmosphere, the heavy rain shower hasn't moved much within the past hour causing some minor flooding.
Additional rainfall of up to half an inch to an inch is possible under the heaviest core. An outflow boundary from thunderstorms earlier this afternoon in Wisconsin has been slowly migrating southwest into southern Wisconsin and could help focus additional isolated showers through sunset. Then our attention will turn to the north and northwest with an advancing cold front. This will be the trigger for showers/storms Thursday afternoon and Friday.
We actually caught a nice view of the rain with our MercyHealth Weather Camera in Beloit looking south. You can definitely see the tall towering cumulus cloud and heavy rainfall. This shower will continue to slowly sink south/southeast through the evening.