Weekend weather update - Includes heat and storms

With the heating of the day Friday afternoon, thunderstorms quickly developed near the Wisconsin/Illinois border near a stationary front.  Those storms did turn severe for a time with pea, up to quarter sized, hail being reported, gusty winds and extremely heavy rainfall.

Storms today also produced a significant amount of rainfall in a short amount of time, causing flash flooding.  And for that, a Flash Flood Warning has been issued for Winnebago and Boone counties until 10:30pm.  Any additional rainfall is not anticipated this evening.

There will be two main issues of concern heading into the rest of the weekend.  The first will be the heat, and second will be additional thunderstorms.  High dew point readings Friday afternoon in the mid and upper 70's is what aided in the torrential downpours.  Those numbers are expected to occur again on Saturday, with temperatures rising into the low 90's.  Because of that, a Heat Advisory has been issued for Northern Illinois and Southern Wisconsin with potential heat index values nearing 105° to 109°.

Storms out west Friday evening will slide, for the most part, northwest of the immediate area by Saturday morning.  Additional thunderstorms will develop mid-day across the Upper Midwest along a cold front.  As the front slides southeast into Wisconsin and Illinois Saturday evening and night, the storm threat will increase through Sunday morning.  Most of the Upper Midwest and Great Lakes has been placed under a Slight Risk for severe weather.  Our storm coverage will increase as the day progresses.

Scattered thunderstorms will continue Sunday, with again, the risk for stronger storms during the afternoon.  This looks to occur mainly south of Rockford, but should the front stall for a time, our severe threat could go up.  While severe weather is going to be a concern both days, any thunderstorms that do develop are going to produce very high rainfall amounts.  So, flash flooding is a big concern going into the weekend in areas that have already experienced flooding issues.