Nighttime storms threaten rare derecho with hurricane-force winds possible in Midwest
Damaging and potentially destructive thunderstorms are set to roar through the northern Plains on Monday, fueled by intense July heat and humidity.
There’s concern that some of these storms could morph into a derecho – a long-lasting line of storms that delivers powerful damaging wind gusts consistently across a few hundred miles of land. Derechos are rare, typically occurring once or twice per year across the US, usually during the summer months in the Midwest and Mississippi–Ohio Valley corridor.
As a result, there’s a Level 4 of 5 risk of severe thunderstorms across parts of South Dakota, Minnesota and Iowa Monday, according to the Storm Prediction Center. That heightened risk level is mainly due to the threat of gusts up to 90 mph. The winds could be comparable to those found in a Category 1 hurricane, albeit in shorter bursts. Category 1 hurricanes have sustained winds of at least 74 mph and stronger gusts.
A few tornadoes could also spin up inside the line of already dangerous storms.
Parts of North Dakota, South Dakota, Nebraska, Minnesota and Iowa surrounding the Level 4 area are under a level 3 of 5 risk of severe thunderstorms that could also bring damaging wind gusts, hail and even a tornado.
A larger Level 2 of 5 risk extends across much of the northern Plains and parts of the Midwest Monday. The main threat is once again damaging wind, but isolated tornadoes or large hail cannot be ruled out.
A few severe thunderstorms blew through parts of North Dakota Monday morning with gusts up to 76 mph. A few storms redeveloped near Montana’s border with the Dakotas late Monday morning and were tracking east in the Dakotas by the early afternoon. From there, storms will tap into plentiful heat and humidity and could strengthen considerably late in the afternoon and in the evening.
The potential derecho is expected to reach its peak strength sometime in the evening in eastern South Dakota or southern Minnesota before tracking into Iowa. The line of storms is expected to gradually lose its strength overnight before it reaches the Great Lakes.
Monday’s storms will be just the latest to hit the northern Plains.
Over the weekend, a cluster of severe storms and tornadoes moved through the region, resulting in numerous wind and hail reports across eastern South Dakota, southern Minnesota and northern Iowa.
Three tornadoes were reported in rural areas. Golf ball-sized hail, downed trees and flash flooding were reported across the Minneapolis-St. Paul area in Minnesota.
Saturated soils from weekend rain are also fueling a flash flooding risk Monday in the northern Plains, particularly across low-lying and urban zones. The Weather Prediction Center has identified a Level 2 of 4 risk of flooding rain across the region.
The severe storm threat lessens to a Level 1 of 5 risk Tuesday as stormy weather shifts south and east into the central Plains and Great Lakes. Those storms will bring yet another chance for flooding, this time in the central Plains.