Depending on where you ski (Parts of Austria + Dolomites) RealityMaps has offline capabilities for the subscription version. The free version will let you use the cached data while offline. They use a very good DEM but have only limited winter imagery coverage. Where available, it's (way) better than Fatmap ever was.
I just checked SkiMoMaps and I'm seeing a mix of autumn and winter imagery with a quite shit DEM in the Alps.
A comparison of some nice lines in Pitztal.
SkiMoMaps:
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RealityMaps (note Airplane Mode, free version)
Attachment 508750
I was playing around with the beta and while the UI is much better (it's a mess now) the cached data thing did not seem to work anymore, so maybe when the new version comes out it's less useful than it is now.
For planning at home in Austria check out also alpinemaps.org. Very high resolution DEM, still working on real snow.