Peter wrote:
"Bob Gardner" wrote

Are you familiar with Skew-T diagrams? They show a continual track of
temperature and dewpoint versus altitude as reflected by the RAOB balloon.
Might be better than depending on rules of thumb. Just Google Skew-T and you
will get plenty of links.

Yes, I use skew-t diagrams. Both actual and forecast. Very useful.

http://weather.uwyo.edu/upperair/sounding.html

http://pages.unibas.ch/geo/mcr/3d/meteo/


I've never used these and didn't know about them. I pulled up a skew-t
diagram from the UWYO site but couldn't figure out what to look for.
Are you looking for altitudes at which the temperature is below the
dewpont and below 0 degrees (and if so, how) or something else?