I don't remember any recent winters when Northern Germany did NOT have a (usually short) spell of snow and ice. I was there in the first week of January this year and there was ice drifting down the Elbe and the Maschsee in Hannover had been turned into a temporary ice rink. And while main roads normally get cleared fairly quickly after a snowfall it's not much fun driving while it's actually snowing.

So, as I said before, anything is possible.