Transition Day - Strong Storms followed by Cooler Weather

It's been a busy day of weather so far across the Stateline. To start our Thursday, we had thunderstorms dump a good amount of rain in some spots. A cold front worked through the region overnight, bringing with it anywhere from 1″ to 3″ of rainfall along and north of Highway 20. You may have been kept up or woken up last night by a few rumbles of thunder. Once the rain moved out, a dense fog layer formed across much of the Stateline dropping visibility down to under a mile for most of the morning. Visibility should improve by the late morning hours. Please remember to slow down and be sure to turn on those low beams if you run into any dense fog while driving this morning. Cloudy skies will remain in place for most of the day.

In fact, flash flooding will possible later today into tonight in portions of southern Wisconsin and in a few counties here in northern Illinois. For that reason, the National Weather Service has placed Jo-Daviess, Stephenson, Green, Rock, and Walworth county under a flash flood watch until tomorrow morning. An additional 1-2 inches of rainfall are expected on top of what we received overnight last night. 

With a cold front located to the south of the Stateline, temperatures today may only climb into the low 80s. It will feel cooler than it has in the past few days. But it will still be a bit humid this afternoon as dew points stick around the mid to upper 60s. That same cold front that passed through overnight will also play a major role in our weather for the rest of today.

As this pushes through northern Illinois as a warm front, a few thunderstorms are likely to form this afternoon. The overall threat for tornadoes remains fairly low, but any storm that manages to cross the warm front could gain a spin. The best dynamics for tornadoes will be out towards the west in northeast Iowa. In terms of severe risks, the Storm Prediction Center has most of the area west of I-39 under a slight risk (level 2 out of 5). The primary concerns with storms that develop later this afternoon and into the evening will be gusty winds and heavy rainfall. Some pockets of large hail are possible with the strongest storms, but this threat is on the lower end of this scale. Just know that with the flash flood watch in place, flash flooding may develop overnight.

Today’s storm chances will come in two separate waves. The first round will likely develop during the afternoon with the lifting warm front. A second line will move through in association with the approaching cold front. It appears the timing with this comes in during the late-evening into the early overnight hours. The time frame that we are looking at for the best storm potential will be 9 PM to 2 AM. We continue to keep a slight chance for a few showers to last into our Friday morning.

Two things will come to an end once this front passes through. One, this boundary will kick out the muggy air mass that has settled over the Stateline the past few days. And two, the active pattern we have seen this week will quiet down a bit as we go into the weekend. Cooler temperatures and windy weather will take over for our Friday as highs only climb into the mid 70s tomorrow afternoon. As mentioned, winds could occasionally gust up to 30 MPH. Temperatures will stay seasonable through the weekend before warming close to the mid 80s by the start of our work week next week.