After a very quiet severe weather across the Stateline thus far, a significant chance for severe weather moves in late Thursday evening and overnight.
Most of Thursday provided the Stateline with a good deal of sunshine and highs back in the lower 90’s. The heat was provided by a warm air mass chasing a storm system to the northwest that will provide the chance for stronger storms later in the night. Early Thursday evening, a line of showers with a few light embedded thunderstorms moved through the Stateline. These elevated showers formed above a capping inversion in a much more unstable atmosphere over northwestern Iowa earlier in the afternoon. After moving into a drier environment over the Stateline, these showers slowly fizzled out as they moved through the area. However, these showers did provide a bit more moisture with more moisture continually flowing into the area from the south through the evening. And while the rain cooled things off a bit, temperatures across the Stateline as of 9:00PM remain in the lower 80’s.
Meanwhile, strong to severe thunderstorms are popping up across east-central Minnesota and sustaining themselves as they move into central Wisconsin. These storms are forming along a cold front oriented northeast to southwest and draped across northeast Iowa and far western Wisconsin. As this front slowly propagates southeastward toward the Stateline, the more active weather is expected to dip southward. Thunderstorms could begin moving into the Stateline from the north as early as around 11:00PM and will continue to fill in over the following several hours. The greatest potential for strong to severe storms appears to be roughly between 1:00 and 3:00AM. The primary area of focus for severe weather sits closer to the Illinois-Wisconsin border although severe storms are possible anywhere across the Stateline.
The primary concerns with these storms are strong winds and heavy downpours. With how dry and hard the ground has gotten over the past several weeks thanks to a severe lack of rain, most of any rain that falls with these thunderstorms will be runoff rather than penetrate the ground. This will lead to the potential for flash flooding, especially in far northern Illinois and in southern Wisconsin where rainfall rates could reach up to 1-2” per hour. Sizable hail is also a possibility but remains more of a concern for our neighbors to the north. The potential for tornadoes appears to be very low though cannot be disregarded. However, the chance for tornadoes has diminished even further through the first half of the evening. Seeing as though the worst of these storms is expected to move through overnight, be sure to have several ways to receive weather alerts including one that is capable of waking you up should you be asleep. Downloading the First Warn Weather app, turning your ringtone on full volume, and keeping your phone at your bedside is a safe bet.