I thought I should give a quick update - the predicted snow did come. I think we had about 15cm, although it's difficult to tell as the storm was quite windy as well (and thundery in some parts of Espoo). Some of the snow had fallen before David got home with the tarps, but he battled the snow, wind and dark to better cover the piles before the rest of it fell.
So that's a good start - our neighbour tells us it's too soft for skiing, but if we have a bit of rain and then some more snow it should be good. At least it looks more like what we expect Finland to look like this time of year, and it's so much brighter outside now which is much better.