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I started my last post by saying the next few days would be steamy, stormy, or in some cases a little of both. Tuesday turned out to be both. Much of the day sunny skies and muggy conditions prevailed. Highs reached 96 in Iowa City and 95 in the Quad Cities and Waterloo. Des Moines out west went all the way to 97. Heat index values were in the range of 100-104 degrees. It was a burner with readings 11-15 degrees above normal near and north of I-80. (see below)


The heat and humidity Tuesday created a strongly unstable atmosphere with CAPE values more than 4,000 j/kg. On the northern gradient of the cape (the ring of fire) strong thunderstorms erupted and began to build southward into the available energy. A severe thunderstorm watch was issued and the emergency manager in Fayette County, Iowa reported 100 mph wind gusts at the Oelwein airport. Corn was flattened around Plainfield, Iowa and in Hanover, Illinois significant tree damage was indicated. Manchester, Iowa was pelted with golf ball size hail and Savanna, Illinois measured wind gusts to 66 mph. The majority of the severe weather reports were received near HWY 20.

Downed tree in Hanover, Illinois curtesy Doug Fillip

Flattened corn near Plainfield, Iowa curtesy of Deb Wheeler, the Iowa Storm Chasing Network


Finally, welcome rain fell in much of my area where it was needed the most. Waterloo, Iowa which had amassed a yearly rainfall deficit of nearly a foot, has now had two consecutive days where more than an inch of rain fell totaling 3 inches. These are the Doppler estimates through Tuesday evening. Everywhere you see blue at least an inch of rain accumulated with the greens indicating 2 inches plus.

So now that we have cracked the nut, can we break it wide open and keep the rains coming? Sometimes you need to prime the well to get the water flowing and hopefully that's the process we just went through. With the storm track in close proximity to the area through Sunday, there's no doubt we'll be seeing more opportunities for rain in the coming days. However, timing, location, and intensity is very difficult to ascertain due to the daily influence of storm generated cold pools and outflow boundaries. That will also have a major impact on temperatures with clouds or rain cooled air limiting heating. From what I've observed tonight, we've seen the worst of the heat this weak although it will remain warm and muggy.

As for showers and storms, I continue with the idea of daily chances Wednesday through Sunday. It may not rain everyday in your location but chances are good some place in my region will see rain over the next 5 days. The next volley is due into the area Wednesday, especially in the morning and across the southern half. The lowest chances appear to be Friday and Saturday. With water vapor levels (PWAT'S) in the range of 1.50 to 2.00 inches through that period, odds are many of you will see at least 1/2 to 1 inch of rain with some spots getting more than that, especially in the north. In general, models continue to show the region from northern Iowa into Minnesota and Wisconsin as the prime area for the heaviest rains through next Monday. That's not set in stone though as MCS complexes could bring that axis further south. No way to know how the convective processes will play out at this point. Here's a sampling of what the modeling is indicating.

The Weather Prediction Center blend out 48 hours.



The Canadian GEM

The 12K NAM (only through Friday morning)

Just for kicks, here's the EURO ensemble's 15 day rainfall departures. Should this verify it will put a serious dent in the drought that has gripped the upper Midwest since spring.

Well, there's plenty of forecast challenges on the table right on into the weekend. With that, I'll call it a day and wish you all a happy hump day. Roll weather...TS


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