Wednesday, July 5, 2017

Storm Outlook for Thursday Evening

We still have isolated storm chances coming up this afternoon, and potentially tomorrow afternoon, but the severe threat increases Thursday evening.

The pattern remains favorable for strong storms Thursday evening as a large ridge develops to the west and a trough develops over the eastern portion of the united states. Upper level winds strength in a northwest pattern overhead which will help to aid in storm development in northern Wisconsin. Winds at the surface will turn to the southwest, this will create wind shear because the wind direction is changing with respect to height. Those low level southwest winds will also advect in warmer and unstable air. As a wave passes through the northwest flow, storms will develop across northern Wisconsin ahead of the cold front. Storms will be strong to severe over Wisconsin where there is an enhanced risk for severe storms across the state. This area of storms will move southeast through the state and will move into northern Illinois.

Model output shows the storms weakening as they move into Illinois, but how quickly that happens is still a question with this system. Right now there is a slight risk for severe storms over northern Illinois. Ample shear and CAPE over the Stateline support the threat for strong to severe storms with damaging winds and heavy rain.

The forecast can still shift and change, but Thursday evening will be a time period to make sure you have a way to receive watches and warnings if they are issued. We will continue to update you as we continue to forecast.

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