Severe Thunderstorms, Flash Flooding Threaten the Midwest through Tuesday

Brian Donegan
Published: September 5,2016
Severe thunderstorms, with damaging winds and large hail, will set up over portions of the Plains and Midwest for the Labor Day holiday. An isolated tornado or two is also possible.
NOAA's Storm Prediction Center has issued a severe thunderstorm watch valid until 3 AM CDT for central and northeastern Nebraska. This watch includes North Platte and Grand Islands, Nebraska. 
In addition to the severe threat, flash flooding is also a concern over the next couple of days because any storms that form will have plenty of moisture to work with, due to a southerly wind flow off the Gulf of Mexico, so excessive rain amounts are possible within a short period of time.

Current Radar with Watches and Warnings

(MORE: View National Interactive Radar Map | Difference Between a Watch and a Warning)
Below is our latest forecast thinking on the timing and magnitude of the severe threats through Tuesday.

Severe Weather Forecast

Monday (Labor Day)

• Forecast: Severe thunderstorms are expected to develop late Monday afternoon into the evening across portions of northeast Nebraska and southeastern South Dakota into much of central Minnesota and far northwest Wisconsin.
• Threats: Damaging wind gusts, large hail and a tornado or two.
• Cities: Sioux Falls | St. Cloud | Minneapolis

Monday Evening's Thunderstorm Forecast

Tuesday

• Forecast: Scattered severe thunderstorms are possible across parts of northeastern Nebraska, southeastern South Dakota, northern and western Iowa, southern and central Minnesota, and western and central Wisconsin.
• Threats: Damaging wind gusts and large hail are the main threats. An isolated tornado can't be ruled out.
• Cities: Omaha | Minneapolis | Mason City, Iowa

Tuesday's Thunderstorm Forecast

Flash Flood Threat

This weather pattern is one in which thunderstorms may train, or re-develop over the same area, potentially dumping large amounts of rain over that area in a short period of time.
Due to this, flash flooding is a concern in addition to the severe weather over the next few days.

Additional Rainfall through Wednesday

A broad swath of 1- to 3-inch rain amounts is expected across parts of the northern Plains and Upper Midwest through Wednesday, with isolated areas seeing upwards of 3 to 5 inches. Keep in mind, a lot of this rain may fall in a short period of time, hence the risk of flash flooding.
The heaviest rain looks to set up over parts of Iowa, Minnesota and Wisconsin.

Severe Weather Setup

As a cold front pushes eastward across the Midwest over the next couple of days, rounds of thunderstorms will pop up out ahead of it, especially during the "heating of the day."
This cold front will interact with a strong low-level jet, or river of fast moving air just above the surface, as well as warm, moist air from the Gulf of Mexico.

The interaction of the cold front and low-level jet will provide the necessary ingredients to produce strong to severe thunderstorms, with damaging wind gusts, large hail and even a few tornadoes.
The warm, moist air from the Gulf will provide plenty of moisture for the storms to work with, creating a risk for heavy rainfall and flash flooding.

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PHOTOS: Plains, Midwest Mid-June 2016 Severe Weather and Flooding