Best indication is to watch the thickness lines on the synoptic charts. As soon we are below 525 it's gonna snow. In my experience the Met Office always seemed to forget we were 526ft amsl - me: "It's snowing", them: "We'll send you a snow warning"
I'm London and the SE, only country bumpkins watch Anglia . . . .
Edited: Got it the wrong way round . . .
