There is a threat for severe thunderstorms over southern Wisconsin this evening. A Severe Thunderstorm Watch has been issued for much of south-central Wisconsin and southeastern Wisconsin until 10 PM. This includes areas south of Wisconsin Dells including the Madison and Milwaukee metropolitan areas.
Shower and thunderstorms have been developing near a very slow-moving cold front which has just moved south of Madison after 6 PM. The highest severe weather threat will be in the warm air south of the front near the Illinois state line, where high winds and hail may occur. Thunderstorms in the cooler air north of the front pose a risk primarily for hail. While the severe thunderstorm threat is highest this evening, additional thunderstorms will continue overnight.
These thunderstorms are capable of producing heavy amounts of rainfall. Rainfall amounts of an inch or two in a short period of time are possible, with isolated areas seeing even higher totals. This could lead to localized flooding in areas that receive heavy rain. Parts of southern Wisconsin in western Grant County and in Green County south of Monroe have picked up 2-3" of rain over the last two days. Additional rainfall may lead to flooding in these areas.
Additional thunderstorms are expected Thursday and Thursday night. The Storm Prediction Center severe weather outlook for Thursday has a Slight Risk of severe thunderstorms over southwestern Wisconsin (mainly southwest of Madison) for a threat of a few severe thunderstorms, while there is a Marginal Risk for isolated severe thunderstorms elsewhere. The greatest threat for severe weather will be from Thursday afternoon through Thursday evening. High winds, hail, and heavy rainfall will all be possible with the strongest thunderstorms. The threat for thunderstorms and for severe weather will end later Thursday night with the passage of a cold front.
Partly sunny skies, breezy winds, along with cooler and less humid weather will arrive for Friday.