Begin: Belle Fourche, SD
Lunch: Newcastle, WY (Mexican joint)
End: Chadron, NE
271 miles
This was the last chase day for Tour 7, and the final chase day of the season for me. We had to be in Denver by noonish the next day, so I was hedging towards playing the NE/WY border area rather than the I-90 corridor through northeastern WY and into SD. Like the day prior, when we chased a prolific tornado-producing supercell, wind shear and instability were quite good. Moisture was a notch or two poorer, though. Dew points today were generally in the 60s, compared to low-mid 70s on June 28. I think that the poorer moisture today was the difference-maker, and the supercell that we watched form southwest of Ardmore, SD, became slightly undercut and unable to become a tornado-producer. A supercell that tracked into the Black Hills did have a tornado with it on this afternoon.
Following a visit to Devils Tower and lunch in Newcastle, we continued south on U.S. 85 to the rest stop at Highway 18. A handful of decent storm towers was developing to our southwest and west, and moving generally to the northeast. I was waiting for one that would be moving into a tongue of good air in the vicinity of Harrison and Crawford, in the northwestern part of the Nebraska Panhandle. Given the sparse paved road network, I was reluctant to head directly to a new cell that was a little northeast of Lusk. We scooted east to Edgemont, and then southeastward to Ardmore. The storm towers, now to our west, were hitting 50k feet on the tops. These sputtered a bit, but a new updraft quickly matured to our southwest, closer to Harrison. We repositioned from west of Ardmore to a few miles south of Ardmore, barely in Nebraska.
The first image above is a look to the west at the earlier activity. Later, the strong RFD cut/clear slot is evident to our southwest in the next-to-last image. I REALLY thought we had a good chance for a tornado as that RFD developed and the action area just to its north began to rotate a bit. Maybe the chance was good, but there was no tornado forthcoming. I was concerned about getting hammered by large hail, so we continued southeastward on Highway 71 towards Whitney, NE, with the storm base approaching from the west. Here, we were suddenly hit by some coolish north winds and outflow. The darn storm base was getting undercut, perhaps by some rain-cooled outflow from the junky storms just to its north.
We stayed with the impressive supercell to Whitney and almost to Chadron, where it weakened near sunset. The views of the structure and hail cores to our north were not bad at all, but this storm was not going to give us anything close to the show we were blessed with 24 hours earlier.
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