Friday Severe Analysis

Update 6:40pm - For all intents and purposes, our storm threat is over for Northern Illinois. Storms up around La Crosse may affect Green, Rock, and Walworth County by 10pm but I have a feeling that most of these will lose their oomph by that time. BBQ: Here I come!

Update 5:20pm - Severe Thunderstorm Warning for eastern DeKalb County until 6pm. This storm will have little significance on our immediate area and will head into the Chicago suburbs within the next hour. Additional thunderstorm development is possible as a Severe Thunderstorm Watch may be issued within the next two hours. Problem is our lack of towering cumulus clouds. Recent check of visible satellite imagery shows very little cloud development west of Rockford.

Update 3:00pm - Reports still coming in concerning today's damaging winds. Area from the Rockford Airport/New Milford area through Cherry Valley and Marengo seems to be the hardest hit with widespread tree damage.

We're still watching the radars and satellite trends closely as the atmosphere is recovering from earlier clouds and rain. This image shows CAPE. Cape is a measure of the amount of energy available for convection. The higher the CAPE, the higher the probability for thunderstorm development (especially with a front in the region). CAPE will continue to rise for another hour or two...then fall. Any severe threat will be limited to the next few hours. As far as the tornado threat? It's not in the cards anymore as winds are generally running parallel to the front at most levels of the atmosphere. I wouldn't be surprised if a few storms sprouted and produced some pea to marble sized hail and more gusty wind.

Update 12:15pm - The strongest winds have already pushed through the region. Still some damaging winds exist around DeKalb and Rochelle, but this effect from the outflow boundary should be ending within the hour.

As you can see, clearing is now taking place over eastern Iowa. This sunshine should heat up the lower portions of the atmosphere to create a very unstable environment. With dew points now in the 60s and a cold front pushing through, I still fully expect some thunderstorms to redevelop during the middle of the afternoon. The main threats from these storms if they turn severe will be damaging winds and hail. Frequent lightning strikes and heavy downpours should also accompany this activity.

This picture was taken this morning by Belinda Sullivan who lives on the east side of Rockford. It shows some of the damage caused by the gusty winds.

(11:55:32 AM) iembot: Malta [De Kalb Co, IL] law enforcement reports NON-TSTM WND DMG at 11:53 AM CDT -- trees down.

(11:43:51 AM) iembot: Marengo [Mchenry Co, IL] trained spotter reports NON-TSTM WND DMG at 11:32 AM CDT -- overturned semi on rt. 20 and i90.

(11:34:28 AM) iembot: Rockford [Winnebago Co, IL] emergency mngr reports NON-TSTM WND DMG at 10:15 AM CDT -- roof blown off a building at rockford airport.

(11:06:18 AM) iembot: Rockford [Winnebago Co, IL] trained spotter reports NON-TSTM WND DMG at 10:55 AM CDT -- small limbs down near intersection of i90 and business us-20.

(11:02:08 AM) iembot: Woodstock [Mchenry Co, IL] trained spotter reports NON-TSTM WND DMG at 10:55 AM CDT -- measured wind gust of 57 mph with 4 foot in diameter tree down and multiple power lines down.

(10:56:51 AM) iembot: 2 Se Mchenry [Mchenry Co, IL] trained spotter reports NON-TSTM WND DMG at 10:45 AM CDT -- wind gusts up to around 40 mph with tree limbs and power lines down.

Update 10:40am = A HIGH WIND WARNING has been issued for the majority of northern Illinois through 1pm. As the storms passing along Interstate 88 continue to weaken they are creating outflow boundaries, which are kicking up very strong wind gusts. The Rockford Airport observation site recorded a 63 mph wind gust at 10:15am. These strong southerly winds will continue for the next 2 to 3 hours.

Original Post = Showers and thunderstorms will continue to move through the Stateline viewing area periodically this morning. The severe weather threat at the moment is quite low here. This current round of wet weather will have a few lightning strikes and rumbles of thunder, but the parameters are not in place for any significant damage. Our risk for severe weather depends upon how much sunshine we see around lunchtime to destabilize the atmosphere and kick off another batch of storms. If the cloud cover stays thick, it will greatly diminish our chances for strong thunderstorms redeveloping. Our slight risk of severe weather entails the afternoon and early evening hours.

A cluster of potentially severe storms around the Quad Cities this morning has prompted a Tornado Watch (indicated in red) for all Illinois counties south of the Stateline. This will run until 2pm this afternoon.

Another problem we are running into this morning are heavy downpours on already saturated grounds. Rain totals at all southern Wisconsin observation sites have broken the 1" mark since midnight. With the heavy rainfall threat continuing, the Quad Cities National Weather Service office has posted a Flash Flood Watch (indicated in green) for Jo Daviess, Stephenson, Carroll, & Whiteside County that is set to run through 10am this morning. -ADAM