In article ,
"Mark Chamberlain (Southend)" writes:
On Tue, 29 Dec 2009 06:47:31 -0800 (PST), MahFL
wrote:

Keith..what do you mean by the crucial 3 C dew point ?


I believe that the dew point needs to drop below 0 C as a snow
indicator. I'm sure I will be put right shortly if i'm wrong

I think that the wet-bulb temperature is the critical one. IIRC that
lies in between the ordinary "dry bulb" temperature and the dew point,
Knowing any two of the three temps, I imagine one could calculate the
third id one knew how.
--
John Hall "[It was] so steep that at intervals the street broke into steps,
like a person breaking into giggles or hiccups, and then resumed
its sober climb, until it had another fit of steps."
Ursula K Le Guin "The Beginning Place"