Severe storms to slice through unseasonable warmth in Upper Midwest

An expansive line of thunderstorms is expected to develop late Thursday afternoon or Thursday evening, across parts of the steamy Upper Midwest, according to AccuWeather meteorologists.

“A cold front will spark the development of some severe thunderstorms Thursday afternoon into Thursday evening across eastern South Dakota, Minnesota and down into parts of northwestern Iowa and northeastern Nebraska,” said AccuWeather meteorologist Rob Richards.

The line of storms is likely to affect Minnesota and eastern South Dakota initially. These thunderstorms will then extend into northwestern Iowa and northeastern Nebraska as Thursday evening progresses.

Already on Thursday morning, a thunderstorm had produced a 59-mph wind gust in northwestern Minnesota.

Before the thunderstorms congeal into a line, some of the thunderstorms will form individually. It is during this time that a brief tornado or two cannot be completely ruled out. However, other hazards will be more widespread.

“The main threats from these severe thunderstorms will be damaging wind gusts and hail,” said Richards.

In the strongest of the storms, an AccuWeather Local StormMax&trade of 75 mph will be possible. For comparison, a Category 1 hurricane in the Atlantic Ocean has maximum sustained winds ranging from 74 to 95 mph.

Due to a ripple of energy in the jet stream, the thunderstorms are not expected to fall apart after the sun sets. In fact, the majority of instances of wind and hail are likely to occur well after dark and perhaps even after midnight.

Before sunrise on Friday morning, the energy is expected to lift to the northeast while the cold front sags southeastward. The separation of the two features will then cause the thunderstorms to weaken and largely fall apart by early Friday morning.

Thunderstorms on Friday will develop from northern Michigan down through southern Nebraska and northern Kansas. A few storms may then get into the Northeast by Saturday. While heavy downpours and isolated gusty winds can occur, widespread severe weather is not expected on Friday or Saturday.

The cold front is also bringing a notable temperature change to the region, but it won’t last long.

Residents of the northern Plains experienced highs more fitting of July or August on Wednesday. For example, Bismarck, N.D., soared to 88 degrees. Typically, the temperature rises to only 74 degrees on Sept. 15. Temperatures will be in the low to mid-70s through Friday in Bismarck before the warmth rebounds.

Elsewhere, Sioux Falls, S.D., will have a high in the upper 80s Thursday, but by Friday, the high will reach only the mid-70s. In Duluth, Minn., a high of 81 Thursday will be followed by a high in the upper 60s Friday.

Warmer air will quickly return by this weekend. Some locations in the Dakotas are likely to be back into the 90s F by Saturday and Sunday. It is not out of the question that a few records highs may even be tied or broken.