'Derecho' in the Conversation, But Not Quite

 

For the first time since last March an SPC Moderate Risk (above) was forecasted into eastern Iowa at 3:00 pm CDT on Monday, July 28, 2025, with higher risks for tornadoes in eastern South Dakota and western Minnesota. Included in this convective outlook discussion was the dreaded word "derecho." (We all remember August 10, 2020...) Indeed tornadoes formed in eastern South Dakota, then turned linear with winds packing 85-100 mph as the storms moved into northwest Iowa by 10:00 pm.

A potent line of storms then proceeded east, maintaining much of its energy along the way. Because of this, the National Weather Service issued Severe Thunderstorm Watch 555 (above) at 10:05 pm CDT. This included north, central and eastern Iowa. 

At 1:25 am CDT, Tuesday, July 29 my weather radio roused me from sleep. Above is a Radarscope image at that moment, with severe-warned storms running from just northeast of Des Moines in the south to around Decorah in the northeast. Some winds in this line were being reported as gusting up to 80 mph. Note the extended severe warning polygons as far east as Delaware and Jones counties ahead of the storm.

2:03 am. At home and spotting from my back deck in the Bowman Woods Park area of Cedar Rapids, Iowa, lightning flickered from behind advancing clouds as seen in this image looking northeast. Image is a  13 second exposure at f/4.5, ISO 250, 24mm focal length.

2:05 am. Cell phone emergency alerts are transmitted, with the simultaneous sounding of sirens in the Cedar Rapids area (for the expected high winds).

2:09 am. The unmistakable structure of a shelf cloud was now moving into the area with high winds. This image looks northeast and is an 8 second exposure at f/4.5, ISO 250, 24mm focal length.

2:10 am. Similar image. Clouds were moving left-to-right in these images. 5 second exposure at f/4.5, ISO 250, 24mm focal length. Nikon Z6ii camera.

Radarscope image for 2:12 am. The blue target icon is my location. Note the significant hail core area between Manchester and Ryan, Iowa. A maximum wind gust of around 60 mph occurred at my location at 2:15 am.

2:24 am. Very large bow echo storm--stretching from Montezuma in the south to Postville in the northeast--but as it turned out, short of the "derecho" criteria. In my neighborhood very little storm damage was evident, mostly twigs and small branches.