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Update 9:45PM CDT... Kankakee County in Illinois and Newton, Jasper, Lake and Porter
Counties in Indiana have been added to the Watch that expires at
Winnebago, Ogle, Lee, Boone and DeKalb Counties have been
dropped from the Watch. _______________________________________________________________ Mesoscale Discussion 1357 NWS Storm Prediction Center Norman OK 0819 PM CDT Wed Jul 19 2017 Areas affected...Northern IL...Southern WI Concerning...Severe Thunderstorm Watch 423... Valid 200119Z - 200245Z The severe weather threat for Severe Thunderstorm Watch 423 continues. SUMMARY...Severe squall line will progress across central into eastern portions of WW423 over the next two hours. DISCUSSION...Long-lived MCS has cycled and matured into a fast-moving complex as it progresses across southern WI and northern IL. Latest radar data suggests the leading edge of a bow-shaped squall line is surging southeast at roughly 50kt. Given this speed/movement it appears the squall line will approach the northwestern Chicago metro between 0200-0230z, and the lake shore around 0230z. There is a possibility for widespread damaging winds along the leading edge of this convection.