The National Storm Prediction Center has issued a mesoscale outlook projecting about a 60 percent probability of a Severe Storm Watch issuance over eastern Iowa, southwestern Wisconsin and western Illinois before 3PM CDT. The affected area is depicted within the escalloped area on the headlined map. Following is the technical discussion:
Concerning...Severe potential...Watch possible Valid 251807Z - 252000Z Probability of Watch Issuance...60 percent SUMMARY...Gradually increasing storm strength and organization may result in a high enough severe threat to merit a watch. Damaging wind gusts are the primary threat, although a tornado or two cannot be ruled out. DISCUSSION...Cold front continues to steadily progress eastward across IA with a developing convective line along its leading edge. This convective line has shown generally steady-state intensity over the past hour or so but the downstream thermodynamic environment appears a bit more favorable for intensification as warmer temperatures promote stronger instability, particularly across eastern IA. Farther east (i.e. northern IL and southern WI), temperatures and dewpoints are a bit lower and the thermodynamic environment does not currently appear particularly favorable. Even so, continued heating plus mid-level cooling associated with the approaching shortwave trough should result in enough instability for storm persistence/maintenance. Linear character of the ongoing storms suggests the primary severe threat will be damaging wind gusts. A tornado or two is also possible with the strongest portion of the line. Warm mid-level temperatures and the resulting lack of steeper lapse rates should keep hail sizes predominately below severe thresholds. Recent trends suggest severe coverage may high enough to merit a watch.