7.7.01 Jewel Cave, SD

7.7.01
Jewel Cave, South Dakota

I decided to drive into southeast Wyoming since most of the recent activity had developed there and then moved into Nebraska and South Dakota. Radar indicated that storms were developing west of Torrington and Lusk, Wyoming. I headed west from Hot Springs, SD on highway 18 hoping to get a good view into Wyoming from the western slopes of the Black Hills. While traveling westbound over the Hills I noticed a strong updraft to my northwest. I estimated the storm to be between Newcastle, WY and Custer, SD which would put it approximately 25 miles to my northwest. I could make out a persistent wall cloud, but I was too far away to verify any rotation. I called the NWS office in Rapid City and reported the wall cloud. They currently were not showing rotation with the latest radar scan.

I continued westbound towards Edgemont, SD. I reached a point were I could see well into Wyoming. I was unable to see any updraft bases, so I downloaded a radar image. The most intense returns were back to the north with the developing storm I witnessed earlier. I decided to backtrack and head north towards Custer. I normally avoiding chasing in the Black Hills due to restricted visibility and limited road options, but I was impressed with the look of that storm west of Custer.

I drove northbound on highway 89, and when the storm once again came into view, it was showing signs of rotation. Striations were apparent in the updraft tower and the base was rounded taking on the classic bowl appearance. I reached a spot just southwest of Pringle, SD that allowed for a descent view of the updraft base. However, I was still approximately 15 miles southeast of the storm. At 641 pm, I noticed a rapidly developing lowering. It was hard to verify rotation from my current position, but by using binoculars, I was able to confirm that this lowering was indeed rotating rapidly. A clear slot appeared to form on the near side of the tornado which allowed downlighting to frontlight the tornado. Trees and a small ridge prevented me from seeing the very bottom of the tornado so I could not confirm if the condensation funnel extended all the way to the ground or if there was any debris. The tornado lasted approximately 3 minutes.

I continued north hoping to find a better vantage point closer to the storm, and called the NWS office. They had just put out a radar indicated tornado warning based on the 648 pm radar scan. Just south of Custer, I once again was able to see the updraft base. The storm structure had weakened somewhat and no funnel was apparent. The storm, however, was putting down some impressive lightning bolts in the vault and forward flank region. The updraft base continued to weaken, but there were still visual signs of rotation. I drove north into Custer and then westbound on highway 16 towards Jewell Cave. Another storm to the west was approaching the same area. While driving through the forward flank of the first storm, I encountered heavy rain, but no hail. Approximately 10 miles west of Custer, I was able to see a gust front rapidly approaching from the second storm. The updraft base was obscurred by precipitation and terrain so I backtracked towards Custer. About 5 miles west of Custer (~750 pm), I had to pull over as I was hit with driving rain and small hail which dropped visibility to less than a quarter of a mile. The hail was mostly pea size with some a little bigger. A sheriff officer was reporting golfball sized hail to my west.

When conditions improved, I continued eastbound into Custer and then northbound towards Hill City. I was able to download a radar image, and it appeared the storms were weakening and developing into an MCS.

Satellite Images of the Storm

545 pm MDT
615 pm MDT
645 pm MDT

Click on images to view a larger version
All times are MDT

	642 pm Looking northwest from southwest of Pringle, SD. Storm and tornado is approximately 15 miles away.
	705 pm Looking west from south of Custer, SD.
	707 pm Looking west from south of Custer, SD.