My standard answer is to wait a couple of months and see who has snowpack and deals. That's low season at most resorts, so you needn't worry about lodging and such selling out.
My secondary answer is to look at Tony Crocker's posts here.
I don't know where you are, but I assume that you're in North America and planning to fly.
Speaking from experience, the only Utah resort likely to still be open is Snowbird. That's not a bad outcome if they've had a good year.
Mammoth will stay open at least through Memorial Day. Since they're the only game in town, they don't typically offer fantastic discounts.
All of the major Tahoe resorts typically stay open at least through the end of April. And many of them, including Squaw and Alpine Meadows, have great spring pass deals by that time. If our snowfall revives as anticipated, you really can't go wrong here.