First, it's nuts to do this for one day. Look hard at adding more days, you've got another month to find a bigger window of opportunity and scrounge-up money. But if it's one day or throw away the plane ticket then - definitely go for it. And SLC is definitely a top contender (specifically Alta) because of proximity of airport to good late season ski areas like Alta, Snowbird, Solitude, Brighton. Renting a car will make life much easier for a quick hit, but SLC has slow public bus/rail combo to slopes. The altitude thing is a definite issue that will have you breathing heavy and could give you mild headache/stomachache on your one big day, although arriving night before helps a little. You're leaving so quickly, if you get a little sick it may not hit you until departing ski area at 4pm. Many people never feel headachy, but all breath heavy first couple days. UT beats most of CO on the altitude issue, except Steamboat is pretty low. What kind of skiing do you like? Check current ski conditions and look at Alta/Snowbird, Steamboat, and Jackson Hole assuming your ticket goes to these places without inconvenient flight transfers/delays. Western Canada is an interesting suggestion because of lower elevations and late skiing, but flight and drive is too far. I think Brighton, UT has night skiing until early April if you want to go really crazy and ski night and day.