What matters when it comes to snow for April skiing:
The rules of thumb in place for better skiing in March—high elevations and lots of north-facing terrain—hold true in April as well. The difference between April and March is that most ski resorts close up for the year by the second Sunday in April. After that, skiers have a much smaller cohort of ski resorts they can target for trips. Many ski resorts, especially those that are easily driveable from the metro areas of Denver, Salt Lake, San Francisco (Tahoe area) and Seattle (Crystal and Stevens Pass) will alter their close dates depending on the quanitity of snow that remains on their slopes in March. More snow means later closing dates.
One of the ski resorts best known for its April skiing is A-Basin, which enjoys myriad factors in its favor. It has exceedingly high elevations, good amounts of north-facing terrain, and it's easily driveable from Denver, which keeps its slopes crowded—and the revenue flowing to resort coffers—well into May.
There are other gems, too, however. Snowbird is an excellent bet, as is Copper Mountain, whose high elevations and preponderance of north-facing terrain means that its conditions don't peak until late March, and the surfaces at Copper tend to hold up well through April. Telluride closes earlier in April because its location doesn't draw many skiers in cars, but that week or two in April that it is open usually offer good conditions, as the resort's high elecations and north aspects keep upper reaches of the mountain chalky, with the slopes to town giving skiers good corn conditions.
For skiers planning ahead for an April trip, just know that it could be quite warm. But sometimes those April days, especially when a big snowstorm creeps in, can be the best of the year, with fewer skiers competing for the snow and fun days that finish with warm après vibes and cold beer. For the record, this writer's best ski day ever was on April 26, in Utah's Little Cottonwood Canyon, at Alta. The mountain had closed in mid April, but then it snowed six feet in four days, and Alta announced it would reopen it's doors on a Friday. Not many people were there, but I was. Laps and untracked all day.
To find out more about where to target for April trips, see our snow rankings page.