The alert amounts apply until Saturday morning, but you can probably drive on Friday if you know your way around.
The core areas: The entire western Alps north slope, but with a core from France to the lower Valais. Snow should also fall further east, although not as much from the Arlberg onwards. As the base is already there, you should also be able to ski.
The snow line should remain powder-friendly and always be below 1000-1200m, in places even down to the very bottom. The full amounts can therefore be expected from 1200-1400m. Saturday will be warmer with sunny temperatures, but it should last until the afternoon.