Dangerous heat on the way

- While so far this summer has been above average, the state has managed to stay away from the truly dangerous heat… until now.  Extreme and dangerous heat will make a fairly lengthy stay across much of Minnesota, Wisconsin, and the rest of the Upper Midwest.  An unusually strong ridge (area of high pressure) will build into the center portions of the country through the week and allow temperatures to soar well into the 90s.  Check out the placement of the ridge and how much it builds from Monday to Thursday…

The jet stream (the blue arrowed line) typically separates us from the truly hot conditions that much of the nation has this time of year because it sits overhead, which holds the heat further south like a lid on a pot of boiling water.  But the ridge building in the central Plains will be large enough to pop that lid and push the jet stream into central Canada.  This pushes heat and plenty of humidity northward all the way to Canada and brings us the hottest weather of the season so far.  But 90s don’t sound so bad right?  Well, unfortunately those 90s come with plenty of humidity.  While we enjoyed the fairly comfortable humidity levels over the weekend with dewpoints in the 50s and low 60s, numbers will soar midweek to the upper 70s and low 80s. 

That brings oppressive humidity levels into play and triggers the heat index (or the feels like temperature) to soar to 110+ degrees.  The only bright side out of this whole scenario is that it won’t last more than a few days.  The truly hot conditions will likely last for about 72 hours from midday Wednesday through Friday afternoon as the ridge breakdown and becomes more elongated by the weekend, allowing a cold front to push through the area on Saturday…

Here is a look at the peak heat index that’s possible from Tuesday through Saturday of this week…