Back Door Cold Front on Sat July 20

During the afternoon and early evening a cold front moved southwest across southern Wisconsin.  A westward moving front is called a back door cold front, unlike typical eastward moving cold fronts. The front was moving at 10 mph and caused a sharp temperature drop and wind shift along its boundary. During the late morning, temperatures near the Lake Michigan shore dropped from the low 80s to the upper 60s to low 70s.  Inland, temperatures ahead of the front were in the low to mid 80s before dropping to the low to mid 70s.  Winds were out of the northwest before the front passed through and turned to the northeast behind the front. 

Along the front there are fairly strong radar returns, but there is no rain. Instead, the radar is picking up mainly dust and bugs caught up in the strong convergence line created by the easterly winds behind the front meeting the northwest winds ahead of it.



 At our office the temperature dropped from about 85 degrees to 77 degrees in about a half hour after the frontal passage. Wind speeds also increased.  An image of the observations taken at our office over the past 24 hours is shown below.





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