no snow in Hafjell Norway

We are arriving in Hafjell Norway on 20th December for a two week stay. Like most of Europe Hafjell is without snow and it doesn't look as though there is going to be any for our arrival.

Unfortunately we are taking friends with us who have never tried skiing before and their kids have been whipped into a frenzy (by us!!) telling them all year how fantastic it will be!!

So, the lack of snow will be bad enough for us and our children, but, dragging our friends to Norway and the expense involved for a hiking holiday feels pretty bad.

Does anyone know if this has happened before?
If it has, then when did the snow arrive i.e. will we see snow in the two weeks?

Any advice at all would be good, but don't tell us to cancel, that will make little excited children cry!