A cold front will sweet through the area this afternoon/evening. It’s expected that surface heating and instability will charge the atmosphere with CAPES as high as 3500 j/kg.
Some factors in thunderstorm development do remain and they are quite common. First is the timing of the front. Personally I’m not terribly worried about this because it appears somewhere in eastern Iowa at least, the front will pass during the crucial “prime time” period of late afternoon/early evening.
Our next major question mark is the always important cap. How strong CINH levels will be remains to be seen. Because waves of energy ahead of the front are unlikely to break the cap, the best guess is storms will hold off until the cold front itself approaches and breaks the cap.
While this will likely delay thunderstorm development a couple of hours, it will also allow the atmosphere more time to destabilize and could lead to rapid and violent thunderstorm development.
The Storm Prediction Center has all of eastern Iowa under what I would call a “high end” slight risk. Tornado risk is somewhat moderate, a solid 5% (see image). But wind and hail threats are pegged up to 30% because of the potential for an organized line that could bring widespread reports of severe weather.
Overall a good chase day could be in the works. Our team will continue to monitor the situation and follow the latest developments throughout the day. For the very latest be sure to stay close to our facebook fan page and for the best updates, subscribe to our twitter.