Drambuster
NB - Parsnip . . . . were you a member of the drama club at school by any chance? 
Nah mate.... fight club... yes
The purpose of my post was to elicit the sort of response from the sort of more experienced here which we have sort of half reached. When does dry snow, which I understand isn't sticking to the flying surfaces, become wet enough to be a cold slurry which then freezes onto cold wings and ailerons and becomes a serious hazard. Thats all really ...on the basis that I'm highly unlikely ever to fly in the stuff I'm not sure that I need to know much more than that which "rather be flying" and "Ghengis" have posted