Active weather pattern set for the next week: Strong storms and heavy rain possible

Strong thunderstorms producing significant rainfall have mostly bypassed the Stateline this weekend but that may change heading into the last week of May.  Even though the weekend has been fairly cloudy and cool we haven't had too much in the way of rain Saturday and Sunday. 

500mb flow
Storm Prediction Center Mesoanyalsis

Heavy rain producing thunderstorms continue to move into southeast Iowa and west-central Illinois Sunday evening following the wind flow at roughly 15,000ft which is from northwest to southeast.  While we have had a few more moderate showers; especially south of Rockford, storms producing 1"-3" of rain this evening have remained south.  Flash flooding has been occurring in eastern Iowa and west-central Illinois. 

The active weather this past weekend has been the result of a stationary boundary positioned from the central Plains to the Iowa/Missouri border and into southern Illinois.  This has kept a cool easterly wind at the surface across northern Illinois and southern Wisconsin keeping our air mass fairly stable.  This boundary, however, will begin to shift north Monday and Monday night bringing the heavy rain threat into northern Illinois and southern Wisconsin early this week.  As it does moisture from the gulf will also lift north with the help of the low level jet and interact with the warm front producing heavy rain and thunderstorms.  The placement of the warm front is critical in determining just where the heaviest rain axis will lie.  Right now, it looks like Monday night into Tuesday would hold the greatest potential for heavy rainfall.  With the warm front in southern Wisconsin Tuesday and weak upper level disturbances moving through the threat for strong to severe thunderstorms will occur and the Storm Prediction Center has the area highlighted under a slight risk for severe storms that afternoon.  The warm front may lift far enough north Wednesday to keep only an isolated threat for storms in the forecast but the main system will begin to shift east Thursday and Friday.  Heavy rain and strong storms will be a big concern heading into Thursday night and Friday afternoon.

The 5 day rainfall forecast is beginning to indicate some locations receiving in excess of 4" of rainfall...additional from what they received this weekend!  Areas across the Stateline could stand to receive 2"-4" of rain by the end of the week.  However, if we experience any training of thunderstorms like what's occurring in Iowa then rainfall totals would significantly increase causing the potential for flash flooding.