Update 12:30pm = DVN issues Severe Thunderstorm Warning for Carroll, Jo Daviess, Stephenson [IL] till 1:00 PM due to the threat of small hail.
DVN: Elizabeth [Jo Daviess Co, IL] trained spotter reports HAIL of pea size (E0.25 INCH) at 12:42 PM -- smaller than pea size hail covering the ground.
DVN: Hanover [Jo Daviess Co, IL] trained spotter reports HAIL of penny size (E0.75 INCH) at 12:31 PM
Update 12:15pm = Dense Fog Advisories have been posted for this afternoon for Whiteside, Ogle, Lee, and DeKalb County. As you can see from the noon observations, visibilities have dropped below 1 mile in these locations and the fog is thickening up a bit in the extreme northern Illinois counties.
Update 11:30am = Radar indicating a storm cell capable of producing penny sized hail just west of the Mississippi River in Clinton and Jackson County. This cell is headed up into Jo Daviess County shortly after noon. No spotter reports of hail from this thunderstorm just yet.
Update 11:15am = Latest model guidance still has us in for a fairly steady rainfall between now and 9pm. After that the precipitation will begin to wind down with just a little light snow to wrap things up.
Update 10:45am = The Storm Prediction Center has updated the slight risk for severe weather today and it is as close to us as I-80. There is a potential for marginal severe weather as close by as the Quad Cities with small hail being the main threat. With strong thunderstorms possible to the south of us and winter storm warnings running for northern Wisconsin, this shows you just how dynamic this system is.
Original Post = As of 8am the skies are completely dry across the Stateline and temperatures in all locations are either at or above the freezing mark. Road conditions throughout the morning look pretty good. Light rain is starting to develop in eastern Iowa and it should swing our way during the late morning hours. This afternoon is when the rain is going to intensify. All of our models our pointing towards a soaking rain of 0.5" to 1" of liquid by tonight. The only counties in our viewing area under any advisories are in southern Wisconsin and this includes Rock and Walworth County. These two counties will be placed under a Flood Watch from 3pm this afternoon through late tonight due to the potential for lots of rain in a short amount of time. A brief changeover into snow could occur between 9pm-1am, but I don't expect any significant accumulations. Snow totals should stay below 1/4".
I am a little concerned about road conditions overnight. There is going to be a lot of liquid laying around when the cold front pushes through and sends our temperatures below 32° in a hurry. This could create a bit of a flash freezing effect, which could create some slick and slippery conditions. I expect the somewhat icy conditions to pop up after midnight when our airmass drops below the freezing mark. Just something to keep in mind as you head out early Friday morning. -ADAM