Sunday afternoon update

6:15pm Update:  Conditions across northern Illinois are being monitored for a possible watch - however there is some uncertainty as to the coverage and intensity of possible storm development.

There have been some isolated storms that have developed southwest of Chicago and those are quickly (around 70 mph) racing northeast.  Because there are no focused boundaries in this area it's a little difficult to try and determine how the coverage of storms will continue into the evening.  Greatest threat for storms appears to be to our southeast.















While there are no severe storms currently, there are a few stronger storms just southwest of Davenport, IA quickly moving to the northeast around 90 mph.  With such a fast movement and strong winds aloft some of that wind speed may be transported to the surface.  Closest county in our area would be Whiteside county.




An elevated threat for stronger storms still exists for this afternoon but there are a few things we'll be watching closely to see how well storms develop.

1:00pm analysis: The cloud cover from storms overnight has cleared out over central Iowa and is starting to thin some across our area.  Low pressure in central Nebraska has been slow to move so far this morning but it will lift into the upper Midwest by late this afternoon and evening; as indicated by pressure falls in north-central Iowa.  Strong southwest winds have been transporting nearly 60° dew points into northern Illinois and with a little increase in the sunshine this will help the instability to rise some.  Looking at some of the mid-day soundings that have gone up and they show there is still a cap (or lid on the atmosphere) in place as warmer air is found aloft.  Closer to the low there are cooler temperatures aloft so those may move east with time into Iowa.  There is also a fairly significant vort max rounding the base of the upper level trough out of the central Plains pointing right into western Iowa.  This would be the area that I would anticipate storms to begin to develop; there are already a few building cumulus clouds noted on visible satellite.  If storms can initiate there they would quickly race east/northeast  most likely in a linear, or squall line, feature with damaging winds being the primary threat.

The biggest wild card will be just how quickly and where storms develop and what type of instability they'll have to work with once they form.  As of right now it doesn't appear as if storms would get here until after 3pm.