Today was the last full chase day for this tour, and we needed to be back in Denver by about noon tomorrow (6/27). The good news was that we were in really good position to chase the moderate risk area in extreme southeastern South Dakota, since we were starting off in Sioux City, IA. The bad news was that if we played this area, we would wind up too far away from Denver at the end of the day. A secondary area to consider was the O’Neill/Atkinson, NE, area; where instability was excellent but surface winds were so-so. We got on a handful of decent storm towers mid-afternoon, and these threw out some one-inch hail stones. The activity up in southeastern SD wound up not being all that great, so we lucked out. Here is the chase account written shortly after the chase:
Our group targeted northeastern NE, a little southwest of the moderate risk area. We waited around Atkinson mid-afternoon as an area of weak surface convergence approached from the west. Winds were backed nicely up in SE SD, but we were stuck with weak winds from the SSW. A strong tower went up to our southwest and croaked. Two additional strong towers went up some 40 miles southeast of there, not too far from Bartlett, and we quickly jumped on them. They became warned and looked promising for about 20 minutes, and croaked. Surface winds were very weak, and it may have been that the weak boundary that aided in convection weakened even further. CAPE values were nearly off the charts, so it was a little surprising that these fairly isolated cells were unable to persist. More strong towers developed to the south towards Albion and looked good for five minutes maximum. Game over. Back to DEN.
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