Severe Threat is Down on Saturday

When I first got into work today and saw that the fine folks at the Storm Prediction Center had north-central and northwest Illinois in a slight risk for severe weather on Saturday, a shot of adrenaline raced through my veins and I immediately started looking at some severe weather parameters. One parameter meteorologists look at for such severe events is called Convective Available Potential Energy, or CAPE. One of our models predicted that we'd have a CAPE value close to 800 for tomorrow afternoon. Depending on the scenario, that is marginally enough for severe weather. But I just checked an updated run from the same model, and our CAPE is now zero. I think the reason for this sudden change is that the warm front that is approaching from the southwest is struggling to move into the area. So we may well stay in somewhat cooler, more stable air on Saturday. A rumble of thunder is a definite possibility, but it appears that the severe weather will stay to our south. Of course, Eric Nefstead will be in the WTVO weather office this weekend to keep you informed on the latest.  --TS