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Severe Thunderstorms, Excessive Rain and Heat Hazards

A Moderate Risk of severe thunderstorms (level 4 of 5) is in the outlook across portions of the Midwest today. Damaging winds, a few tornadoes and frequent lightning with heavy rainfall are in the forecast. Meanwhile, dangerous heat across the southern Plains into the Great Lakes, mid-Atlantic and Northeast will expand into Friday. Risk for wildfires for the central Rockies and Sacramento Valley. Read More >

Overview

A strong upper-level low pressure moved from the Rockies on May 5, 2024, to the northern plains on May 6-8, 2024. Deep surface low pressure developed over southwestern North Dakota. Ahead of the system, strong gusty southeast winds developed on May 5 pulling in plentiful moisture. As the system strengthened May 6-7, strong northwest winds (up to 79 MPH) developed with heavy, wet snow over the highest Black Hills. Numerous power outages were reported coincident with the snow and high winds.

As the two air masses clashed, a line of thunderstorms developed on May 6 in the morning. The thunderstorms produced minor flooding in Gillette, WY. Over western South Dakota, a line of thunderstorms developed – containing isolated severe thunderstorms – with one storm producing two tornadoes near Mud Butte, SD early in the afternoon on May 6.

Significant liquid-equivalent precipitation fell. 1 to locally 3” fell over northeastern Wyoming and the Black Hills. Amounts on the western South Dakota plains varied widely with some folks getting very little and others around an inch. 14-18” of snow fell near Four Corners, WY, and O’Neil Pass, SD.

Deep snowcover on a ranch with a barn in the back
Moskee, WY
Courtesy Becky Stoddard
Flooded intersection with stoplights
Gillette, WY
Courtesy David King
Deep snowcover on a ranch with a barn in the back
Near Mud Butte, SD
May 6, 2024 1245 PM MDT
Courtesy Joshua Tatman
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