May 29, 2011

May 29: Cheyenne Ridge area of extreme se Wyoming/ne Colorado

 9:44 PM MDT Update:  Well, my estimate that the convective inhibition would fade away by late afternoon was way off mark.  We called it a chase at around 6:45 PM.

5:13 PM MDT Update...Sitting near I76 south of Fort Morgan or so, awaiting whatever might happen.  Right now, not much.

The target seems too obvious...and I hope I am not deluding myself because I am in Denver right now. The models paints a very favorable picture for both supercells and a possible tornado along the Cheyenne Ridge this afternoon. Ahead of the deep trough coming into the Four Corners area under 40 to 50 knot 500 mb flow...the RUC has a surface cyclone correctly initialized this morning. During the day this intensifies and channels strong east southeast flow into Colorado bringing really high dew points for this part of the Plains into ne Colorado and then up the Cheyenne Ridge. Will 55 to 60 F dew points actually make it into this area, which currently has 40s? My guess is the foggy air all over this area currently has 50s dew points.

Upstream in the surface flow in KS are the 60+ dew points in southeast flow moving this way. The model takes the surface low northward and centers it in north-central Colorado this afternoon and I can't believe my eyes that it has surface southeasterly winds of sustained 20 knots or so over the region, and with a great angle with respect to the Cheyenne Ridge.

Throwing caution to the winds, because as soon as I point this out, the next run will evaporate it, I see the RUC breaks out precipitation there and has what looks like a supercell east south east of Cheyenne. As others have pointed out that starts out in the mountain convection around 20 UTC or so, and has a very good look around 22 UTC. I plotted a sounding and hodograph from the RUC for that location for 0000 UTC. Those are to the right.

While I'd like to see more turning in the hodograph in the lowest 3's pretty good. The sounding says that LCLs will be low too, but there are some CAPE-robber qualities in it. That elevated inversion was there in all the forecast hours, but was very strong in the initialization and systematically weakens. Finally, yes, this is all contingent on the fog clearing out. Not the initiation in the mountains though....that will happen. I'll wager the soundings evolve sort of like the one I have below, because the fog will have cleared out.