Pattern breakdown leads to a gradual increase in thunderstorms heading into the 4th of July weekend

 For the third day in a row, afternoon temperatures have warmed into the upper 80s and low 90s, with the heat index climbing to 100 (or higher). Extreme Heat Warnings remain in place through tonight for Stephenson, Jo Daviess, Carroll counties and until Thursday night for Whiteside, Rock, Green, Walworth, Winnebago, Boone, Ogle, Lee, DeKalb, and McHenry counties.

Isolated thunderstorms developed over parts of northeast Iowa earlier Wednesday afternoon, shifting northeast into Wisconsin but had a hard time maintaining their strength and were quick to dissipate over Green County. With skies beginning to clear Wednesday evening the chance for any thunderstorms locally remains very isolated. It'll continue to be a hot and muggy evening/night.

Storms are likely to get going over the next few hours from parts of Wisconsin, back through Minnesota and Iowa. This is where the stalled cold front/stationary boundary resides. While most of those storms will remain to our north overnight, the slight shift in the upper-level ridge will set the stage for a little further southward development of any storms tonight. This could lead to an isolated storm or two moving into parts of southern Wisconsin and northern Illinois through sunrise Thursday. The main threat for any severe weather resides to our north, but a gusty storm or two may occur locally should any storms move towards the state line late tonight.

While there may be some impact with regards to temperatures Thursday morning, the expectation is for highs to climb back into the upper 80s and low 90s. As the stationary boundary stalls a little closer to the state line the chance for showers and thunderstorms will gradually increase through the weekend, but it doesn't look to be a complete washout.

Heading into Thursday evening we'll need to keep an eye on any storm that develops locally as there could be a risk for a severe storm or two. Southern Wisconsin and some of northern Illinois are under a 'slight' risk for severe storms Thursday evening. A 'marginal' risk for an isolated severe storm is in place for Friday. Should any storm reach severe limits it would be capable of producing strong winds and hail.