Storm Threat Heading Into the Weekend

Showers and isolated thunderstorms have developed over southern Minnesota and northern Iowa Wednesday evening along and ahead of a warm front.  Temperatures south of the front are in the middle 80's while north of the front temperatures are in the 60's and 70's.  Moisture beginning to lift north from the Gulf of Mexico has helped fuel the development of that cluster of showers/storms and will continue to do so through the evening and overnight.

Most of the activity through the night will remain west and actually decrease a little in coverage with new storms developing later tonight.  It's the development of those later storms that we'll have to watch for the possible progression into northern Illinois and southern Wisconsin by Thursday morning. 

The storms will all be possible by a couple factors: the low level jet and warm front.  The low level jet is more of a nocturnal jet - meaning - it develops during the evening and overnight.  It can still be present during the day, but might not be as strong.  As the winds within the low level jet encounter the warm front, thunderstorms develop.  Storms that persist through the night for a long duration of time are often times fueled by the low level jet.  With the warm front staying just to our south Wednesday night and Thursday morning, storms that develop over Minnesota and Iowa will follow the front and track southeast.  Most likely they will be weakening as they do so, but I still expect parts of the area to be waking up to rain and thunderstorms during the morning.

These morning storms may last through mid to late morning with a break occurring during the afternoon.  During this time the warm front will try to make progress to the north but that may be cut short due to the morning rain.  As the low level jet picks back up during the late afternoon and evening, new storm development along the front will occur.  The question heading into Thursday will be where the front ends up and just how much instability can build south if enough clearing takes place.  Right now it appears as if any afternoon/evening storm development will be in southern Wisconsin and northeast Illinois.

By Friday the warm front should be far enough to the north to keep most of the afternoon dry.  Friday night could be interesting with a cold front moving south out of Wisconsin.  Heavy rain producing thunderstorms may accompany the front and those could end up in southern Wisconsin by Saturday morning.