All the ingredients for an explosive severe weather event will be in place this afternoon. Extremely high CAPE values that could approach 6000 j/kg, A CINH value that could top 200 will prevent development until the cap breaks this evening and shear values that will permit the formation of supercells.
The one kink in all this thinking is the cold front that’s supposed to be the focal point of severe thunderstorm development. Take a look at the picture to the right, this is the forecasted position of the front at 0Z (7pm Monday Night).
The current forecast puts the “triple point” right over the Quad Cities area with a cold front draped across extreme southeast Iowa. 7PM could be the time we see the first storms take shape across Iowa. This placement is not ideal. The front will spend the afternoon moving north to south across eastern Iowa. But with a strong cap in place, it’s not expected to be strong enough to touch off any storms before the early evening hours.
Therefore, the Storm Prediction Center has backed off on its risk area to include only portions of southern Iowa. This is not ideal for a chase simply because we could quickly get out of position if we have to chase after the storms rather than get in a position where the storms come to us. We will continue to monitor the situation throughout the afternoon. If the front stalls before passing through Iowa, or the cap is not as strong as expected, earlier development could increase the threat to eastern Iowa.
But at this time, looks like a very stormy evening along the Iowa and Missouri border. Beyond tonight, several rounds of rain possible over the next few days. Right now there are no threats posted for eastern Iowa, but that could change as the weather pattern remains active.