National Weather Service United States Department of Commerce

Overview

On the afternoon of July 6, 2020, powerful thunderstorms developed across northeastern Wyoming and southeastern MT. They merged and strengthened as they moved over Sundance and into the Black Hills area.

The first tornado of the day was confirmed by video and began approximately 8 miles NNW of New Haven, WY. This tornado moved southeastward for approximately 8 minutes, traveling over largely unpopulated portions of northwestern Crook County with limited vegetation. Due to a lack of discernible damage, an official rating for this tornado could not be determined. Several other funnel clouds were reported around the Sundance area, and Sundance received some wind damage from the storm.

Another tornado was reported south of Cement Ridge in the northern Black Hills, which resulted in widespread snapped and uprooted trees. The tornado lasted for approximately 20 minutes and traveled for over 7 miles, crossing the state line from southeastern Crook County into western Lawrence County. The scope of tree damage, with a swath nearly half a mile wide at times, indicated that this was a significant tornado. This damage was consistent with estimated maximum wind gusts of 120 mph, corresponding to an enhanced Fujita scale rating of EF2.

Tennis ball to baseball sized hail was reported over parts of northeastern WY, the Black Hills, and the Rapid City area. As the storm tracked eastward, it developed into more of a wind producer. Winds up to 75 mph were reported across parts of south central South Dakota.

Image
12 mi SE Rapid City
(B. Fleming)

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