(KIMT) — December 15, 2021 is a day etched into the record books, not just for SE Minnesota and North Iowa, but for the United States as a whole. Before December 15, 2021, a derecho has never been recorded in the United States. This impressive feat remains intact to this day as the only recorded December derecho to ever occur in the United States.
A derecho is a long-lived line of severe thunderstorms with a wind damage swath of more than 240 miles. Additionally, a derecho will pack wind gusts of at least 58 MPH or greater along most of the length of the storm’s path. Derechos most commonly occur during the warm, summer months in the Central Plains and Midwest.
To start, the Storm Prediction Center issued one of the highest threats for severe weather so late in a given year. A Moderate (level 4 out of 5) Risk was issued throughout SE Minnesota and North Iowa for the December 15th event.
Records were shattered when it came to the number of warnings issued so late in a “severe weather season”. A slew of Severe Thunderstorm Warnings and Tornado Warnings blanketed the region.
Damages were brought regionwide due to short-lived tornadoes and damaging straight-line winds within the derecho itself.
Additionally, several all-time December temperature records were set as record warmth baked a snowpack that was only a few days old.
After the derecho passed, destructive winds pounded the region with widespread 60-80 MPH wind gusts. This led to even more damage, especially to trees and farm buildings. Countless locations suffered power outages, structural damage to buildings, and tree damage. Rochester International Airport (RST) recorded its second-highest ever wind gust on record at 77 MPH.
Overall, this was a historic outbreak that did not just impact SE Minnesota and North Iowa. Record warmth, rapid snow melt, dense fog, tornadoes, and widespread damaging winds occurred. During the event, there were 94 tornado reports, 564 damaging wind reports, and 22 hail reports. Specifically, 64 reports of winds greater than 75 MPH were sent in, and 4 reports of hail greater than 2 inches. Over 600,000 people lost power and an estimated 1.8 billion dollars in damages occurred.
For more information regarding this historic event, you can click on this link.