I put together a new case study (10 July 2009) showing how 700 mb temperatures can be helpful in estimating the location of an inhibiting capping inversion:
10 July 2009 "cap" case study in the central plains
I've also updated my original material that is an informal reference about using 700 mb temperatures as a first guess estimate of the "cap":
Using 700 mb temperatures as an estimation of the "cap" in the central plains
There are several caveats given, including the fact that the 700 mb temperature values often don't work well in the High Plains and westward due to surface heating over elevated terrain in the warm season, and also upslope situations. Although only a very rough guide, the table and information with this material can be useful in raising awareness about possible "cap busts" when forecasting. Hope some find these useful.
- Jon Davies 8/17/09