June 15, 2013 Atwood, CO supercell sunset

June 15th was the changeover/down day for Tempest, between tours 6 and 7.  Our group began in Kimball, NE, and made the easy drive into Denver to drop the guests off.  Tour 7 would begin the following morning.  There was a risk of severe weather in northeastern Colorado, however.  SPC showed a slight risk over much of northeastern CO, with a 5% tornado area.  Instead of washing the van and getting the oil changed, Chris G. and I grabbed a couple of stray Tempest guests and headed back out to onto the High Plains Playground.

It looked like the favored area for initiation would be the Cheyenne Ridge, and we needed to be in position to catch any cells coming off of the ridge and moving to the right, into northeastern Colorado.  We watched a storm cell sputter for a while near the CO/WY/NE triple point.  We stayed on its south side from about Grover, eastward to Highway 71.  After an hour or two, the storm began to look more like a supercell, with a big clear slot and a large base.  It began to move more to the southeast as we and it neared Highway 71, and some ping-pong-ball-sized hail bounced off of the van.  The road network was kind of sparse, and we decided to go into “structure observing” mode by heading south to Highway 14.

As you can see, the storm was isolated and picturesque, but it was high-based and less-than-amazing structurally.  Our group watched from Highway 14, west of Sterling, for quite a while as the cell drifted off to our northeast.  It didn’t seem like there was any good reason to stay with it, especially because we would be going back to Denver this evening.  But, new updrafts were rapidly going up just to our south!  We went south maybe 8 miles or so, and stopped beneath an active updraft base.  This was also high-based, but a great RFD cut was causing plenty of swirling motions and impressive cloud features nearly overhead.  This was not too far from Atwood, CO.

As the sun set and the light softened, the colors on the back end of the cell to our east just got better and better!  We were glued to our cameras and very happy to be in eastern Colorado!  On our way back to Denver, we stopped for a while near Snyder to shoot the lightning with a weak cell to the west.