Although it did bring power lines down, it was thunder snow that evening.
I was a young scout leader at the time, and we had taken the scouts out on a Night Hike in Sutton Park (so you can tell it wasn't forecast!). We sent them all off in patrols to do the route at about 11pm, and within an hour the we started to see lightening on the horizon, followed very quickly by snow starting to fall. Within 30 minutes it was so torrential we were driving round Sutton park like mad things trying to round up all these kids in the dark!
The plan for the evening was that they were all supposed to sleep at the church hall on our return, but we drove them all home, banging on doors at 1 in the morning to wake their parents up because we could tell we weren't going to be able to get them home in the morning.
When I did get up later that morning the snow had drifted so high up my front door there was a wall of it when you opened the door!
Quite a night!