We are half way through the meteorological summer. School supplies are already making their way to the store shelves. We have begun to notice the later sunrises and the earlier sunsets. Earlier this week overnight low temperatures slipped into the 30s in the typical cool spots of northeast Minnesota.
It has been especially humbling the last few days with regard to predicting precipitation accumulations. Computer models paint most likely areas for a good soaking, but the convective development can be impacted by outflow boundaries from decaying storms.
Thunderstorms tend to fade in the mid morning as noted by the old folklore, rain before 7am ends by 11am. Left over cloud debris shields the landscape and inhibits heating that creates instability. Forecasters monitor satellite imagery for the boundary of the clouds and sun. This creates what we call differential heating. Thunderstorms often form along these boundaries, typically drifting south and east into the more favorable unstable air.
No doubt, the records indicate that the Twin Cities metro area has been one of the driest regions since June 1st. For example Duluth has tallied over eight inches, St. Cloud 5.41 inches and Redwood Falls 4.93 inches (a very welcomed rain fell yesterday). Twin Cities International Airport has accumulated only 4.51 inches.
To our south, soaking rains have been experienced. Rochester has received 9.39 inches, LaCrosse 13.32 inches and nearly sixteen inches at Madison, Wisconsin during the first half of the meteorological summer.
The Climate Prediction Center has already released the outlook for August without much fanfare.
Showers are in the forecast for the weekend, but I wouldn’t necessarily start altering outdoor plans. Perhaps the thunderstorms will rumble during the cover of darkness.