Could this be a 1978 repeat? Reading the snow forecasting thread at the moment!! "Another situation is when you have high thicknesses and higher 850mb temps, but a cold undercut (continental typically), here wet bulb will be several degrees below zero, so snow is more likely than rain as the cold air at the boundary layer undercuts the warm air aloft. (this was responsible for the blizzrds in the westcountry in feb 1978, thicknesses here were well above 528 and 850mb temps in the SW nearer to 0 to +1C."