Tuesday, July 19, 2011

What more can we say about the heat....

...except it's going to last awhile!  First off, Excessive Heat Warning continues through Thursday for Green, Rock, Walworth, Stephenson, Jo Daviess, Carroll and Whiteside counties.  A Heat Advisory will remain in effect for Winnebago, Boone, McHenry, Ogle, Lee and DeKalb counties through this evening.  An Excessive Heat Watch will then go into effect for those following counties Wednesday.  The reason - simply put: it's going to get very hot. 

The center of the upper level ridge has been centered across the middle of the country the past couple days placing the Great Lakes in what's known as 'northwest flow'.  This means the upper level winds are coming in from the northwest, even though our surface winds are coming in from the south.  With this flow storms tend to form across the northern Plains and dive southeast as they follow the flow of the jet stream (which has been happening for the past couple of days). 

By Wednesday the center of the upper level ridge will shift a little further east as an area of low pressure moves across southern Canada.  This will change our northwest flow to more of a southwest flow, causing temperatures to warm even more as our threat for any storms or cloud cover decreases.  Right now I'm going with a high or 97° Wednesday afternoon.  The last time we hit 100° was back on July 10th, 1989!  If we have too much moisture in the atmosphere we probably won't be able to hit the century mark but either way you look at it, it's going to be very uncomfortable Wednesday.

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