Today is a day to be "weather aware" as there is a significant risk of severe weather including damaging hail, wind, and a few tornadoes. On our Threat Track scale, we are at a level 3 on a 1-5 scale. The main threats will include damaging wind, hail to the size of golf balls, and a few tornadoes.
Here's the set up: There will likely be two windows of opportunities for storms today. First, non-severe thunderstorms will traverse the area from southwest to northeast between 7 a.m. and 10 a.m. These storms could be near-severe when it comes to some hail, but are not expected to be overly dangerous. Storms that use heightened storm energy (CAPE) will form massive updrafts, turning severe quickly.
Here's the timing of the most intense activity. We expect them to move into our coverage area southwest of the Quad Cities early this afternoon. These will be rooted in an environment that is much more unstable and includes wind shear...especially as we head into peak-heating of the day, around 4 p.m. The pattern is not completely different from last Friday when tornadoes affected the Macomb and Iowa City areas. This threat will be centered in the northern half of Illinois. The Storm Prediction Center is also forecasting the possibilitly of a few "strong tornadoes."
A "strong tornado" is classified with winds over 111 mph. According to the University of Illinois, Only 3 in 10 tornadoes ever mature to this stage.
Cities most at risk include the Quad Cities, Sterling-Rock Falls, Princeton, Rockford, DeKalb, and Chicago. All lie in the significant risk of severe storms today.
Storms will weaken around sunset as they translate east into the Chicagoland area. Again, our threat of severe and possible tornadoes will be between 1:00 p.m. this afternoon and 6:00 p.m. this evening.
-Meteorologist Eric Sorensen