Severe Weather Outbreak, Including Widespread Damaging Thunderstorm Winds, Likely in the Midwest Wednesday

June 21,2016
An outbreak of severe thunderstorms appears likely Wednesday and Wednesday night in parts of the Midwest, with the potential for widespread damaging wind gusts over several states from the southern Great Lakes to the Ohio Valley.
Low pressure pushing east along a warm front separating oppressively hot air from cooler air while being accompanied by a mid-level atmospheric disturbance is the setup for this potentially volatile severe threat.
Derechos, long-lived and widespread thunderstorm wind damage events, sometimes develop in this type of atmospheric setup, though it remains to be seen whether one of those will develop Wednesday or not.
(MORE: What is a Derecho?)

The setup for a potential severe weather outbreak Wednesday and Wednesday night in the Midwest.

In the meantime, some severe t-storms are expected to flare up in a broad zone from the Mid-Atlantic states to the northern High Plains.

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 Thursday.

Severe Weather Forecast

Tuesday-Tuesday Night

• East: Along the stalling west-to-east aligned front, scattered strong to severe thunderstorms are likely to develop from parts of the mid-Mississippi and Ohio Valleys into the mid-Atlantic states. The main threats are damaging winds and large hail. Locally heavy rain and isolated tornadoes are also possible.
• Northern Plains: Scattered thunderstorms in northeast Montana with hail, a few tornadoes, and damaging winds should congeal into a late-night t-storm cluster tracking across parts of North Dakota and western Minnesota with strong wind gusts possible.
• Upper Mississippi Valley: A line of thunderstorms should form after midnight from parts of South Dakota and southern Minnesota into Iowa, western and northern Illinois. Large hail and locally heavy rainfall, triggering flash flooding, are possible.
• Cities: Washington D.C. | Richmond, Virginia | Bismarck, North Dakota | Davenport, Iowa

Tuesday's Thunderstorm Forecast

Wednesday-Wednesday Night

• Morning: One or more clusters of t-storms from the Upper Mississippi Valley into the Ohio Valley will be capable of strong wind gusts, large hail and locally flooding rainfall. 
• Late afternoon: Discrete supercell thunderstorms (particularly in western part of severe risk area) pose a threat of large hail and a few tornadoes.
• Night: Activity should congeal into a large squall line of t-storms in parts of Indiana, Ohio and southern Michigan by evening, pushing east-southeast into the central Appalachians late with a threat of widespread damaging straight-line winds, possibly leading to numerous power outages, downed trees, and perhaps some structural damage.
• Cities: Chicago | Indianapolis | Cincinnati | Louisville

Wednesday's Thunderstorm Risk (NOAA/SPC)

Thursday

• Morning: We can't rule out the previous t-storm cluster/squall line surviving into the Mid-Atlantic states or Applachians Thursday morning, with straight-line high wind gusts the primary threat.
• Afternoon/evening: Otherwise, widely-scattered severe t-storms may fire up in the afternoon and early evening along the frontal boundary from the mid-Atlatnic states and central Appalachians to the central High Plains of the Rockies.
• Cities: Cincinnati | Denver | Washington D.C.

Thursday's Thunderstorm Forecast

Storm Reports Recap

Monday

Strong wind gusts took down trees and power lines in parts of Indiana, Illinois and Missouri on Monday afternoon. The threat shifted eastward by Monday evening, taking down additional trees and power lines in portions of Upstate New York. Additionally, some small hail was reported in places like Rochester, New York, late Monday evening.

Father's Day Weekend

Hail as large as tennis balls, teacups and even grapefruits struck Minnesota Sunday evening as severe thunderstorms rolled through the state.

One tornado was reported near Staples, Minnesota, Sunday evening. No injures were reported from that. However, strong wind gusts knocked a large tree onto a home in Deerwood, Minnesota, trapping three in the home and injuring one.
(LATEST NEWS: Injuries Reported in Minnesota Storms)
The same cold front brought severe weather to northeast Montana on Saturday. Hailstones up to 4 inches in diameter were reported in Wolf Point. A few locations measured wind gusts in excess of 70 mph.

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