Forecasting Severe Weather can be tricky business

                            Issued 245 pm CDT Fri Jul 12th

The potential for severe thunderstorms with damaging winds was rather high on Tuesday July 9th 2013 along the WI/IL border but did not develop as expected.  There were a few severe storms including 3 tornadoes in central WI but no severe weather was reported in the Milwaukee or Chicago areas. 

However, the very next day, Wednesday July 10th, featured a significant severe outbreak in the Ohio Valley where over 500 reports of severe weather were received.  This included several measured wind gusts of 80+ mph. 

This scenario does occur on occasion with severe thunderstorms and even winter storms.  The pattern becomes favorable over a period of a few days and sometimes is only realized on one of the days.  Sometimes the day before, sometimes the day after.  Since weather systems often move from west to east, if there is a delay, then you often see the severe weather a few states downstream or to the east.  This was the case. 

The images below show the observed severe weather on July 9th and July 10th and the associated Day 1 Storm Prediction Center severe weather outlooks.  Yellow areas indicate a Slight (SLGT) Risk (15% or greater probability of severe weather within 25 miles of a particular location).   

Jeff Craven,  Science and Operations Officer

National Weather Service Milwaukee/Sullivan WI 

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