Every year I've been in Arinsal (since 2005) there's been enough snow to ski the first week of April, although the condition of it does vary somewhat. Normally when it gets to April it's pretty warm in the daytime so you just need to hit the slopes first thing and then after lunch enjoy the apres ski in the sunshine. Last season finished with a depth of 90-140cm.

Arcalis is also included in your lift pass and they usually have skiing until the end of April and occasionally into May.