Attention is focused on a very well organized bow echo complex that's been going on over Iowa and Southern Minnesota this afternoon and evening. As expected, it is making a turn to the ESE, which would point right toward to the Stateline. Here's the BIG WILDCARD though. A lake breeze developed this afternoon and has pushed westward, allowing for quick cooling to take place in some areas, especially East of I-39, thus making the airmass decidedly more stable... Meanwhile, the air closer to the Mississippi River is considerably more unstable. Storm complexes like these will tend to follow the more unstable airmass, which would suggest perhaps a more dramatic shift SE with time.
There are two different scenarios I see happening. Scenario #1 (probably the more likely): The storm complex follows the axis of greater instability, which would favor areas further west (Green, JoDaviess, Stephenson, Carroll, Whiteside, perhaps western Ogle and Lee Counties) for damaging winds. Scenario #2: Storm continues on current track, produces gusty winds in the West, but weakens as it moves closer to Rockford and points East as it encounters the more stable air present here. We'll have to monitor the westward progress of the Lake Breeze in the coming hour. The further that lake breeze pushes west, the smaller severe threat we'll have.
Many times the complex will try to steer away from the colder airmass. Cold airmasses are a death sentence to storms, so many times you'll see them try to follow the path that would allow them to survive the longest. If this is to happen, there's a chance that very little happens here in Rockford, while big winds could impact the Westernmost parts of the area. If the complex does reach the cooler airmass, you'd see a RAPID decline in the intensity of the system!
We're cooling rapidly, now down into the 60s as far west as Freeport... Given the fact that winds are out of the E and NE across most of the viewing area, our airmass should continue to stabilize in the 2-3 hours that it would take the storm complex to reach here. That would take a good bite out of this system. Nearest thinking here is that on a scale of 1-10 the chances for Severe Weather for Rockford and any point east is a 2, for Stephenson, Western Ogle, Western Lee Co a 3.5, Jo Daviess, Carroll, Whiteside Co a 5. But we've got some time to keep watching this, and we'll do just that!
8:15 PM UPDATE -- As of 8:00PM, Rockford's Temperature and Dew Point have both fallen by 4° in the past hour. Temp's down to 64° and Dew Point down the 54°, indication of the rapid stabilization of our atmosphere, and a lowering of our severe weather threat. It's not gone yet, but it's going down quickly.
With this significant temperature decline in mind, it comes as no surprise that the Storm Prediction Center has removed all of Northern Illinois from the Severe Weather risk for the remainder of the night. Still wouldn't be surprised if we had a 40-50 MPH gust with this complex, but with the atmosphere continuing to stabilize every passing minute, the severe threat is looking extremely minimal! Another bullet appearing to be dodged!! We'll update as needed as the complex continues to slide ESE.
10:00 PM UPDATE: As expected, the complex of storms has encountered the cooler, drier, more stable air and has essentially been torn apart. Severe threat is zero the rest of the night.