Hi Will, I don't know if you remember many years ago sending me a
little
simple rule of thumb for estimating the different probabilities of
snow risk, based on adding the DP and temp together. Well I've used it
ever since and it has proved to be very accurate on many occasions,
today being one such.
I realise there are other more sophisticated factors, evaporative
cooling etc. but it has nevertheless proved extremely useful
Thanks,
Dave

I'm intrigued now Dave .. share it with us all please.

==== Will's rule of thumb ====

Hope he doesn't mind me re-posting his post....

"I have a rule of thumb which has worked for over 30 years!
Just add the temperature and dewpoint together in the rain and call the sum
S.
If S is =7 prob turning to snow in the next half-hour is 10%
S =6 prob is 20%
S =5 prob is 30%
S =4 prob is 40%
S =3 prob is 50%
S =2 prob is 60%
S =1 prob is 70%
S =0 prob is 80%

(S 7 prob is NIL)

E.g. T 5.0 D -2.0 gives S=3 and a snow prob of 50%
T 3.0 D 3.0 gives S=6 and a prob. of 20%
T 7.0 D -6.0 gives S=1 and a prob. of 70%

HTH
Will"

Joe