help with skiing

Am booked to ski at Shiga Kogen Apr 6 to 10 but just saw on snowjapan's sight that the next few days will be warm at Shiga so most of the snow may have melted. The snowjapan site for Shiga (and indeed all ski resorts) only go as far as March 22, does anyone know of a site--even if in Japanese which will forecast the temperature at Shiga to say April 6 as we need to confirm or cancel our ski booking in the next day or so.

This is Japanese HP
It said most ski place planned to open untill April 5. But it depends on place.

http://www.shigakogen-ski.com/spring.htm

I'm not sure that you'll be able to get an (accurate) weather forecast for three weeks in advance of the day you'd like to ski...But even without a weather forecast, my gut instinct is that you'd be taking a pretty big risk - even if there is still snow on a few runs, I can't imagine that conditions would be good enough for you to enjoy 4-5 days of skiing. Unless you are coming from a place where it never snows, you might be disappointed. If your trip is based in Tokyo, you might consider leaving space in your itinerary for taking a day trip to Kagura or Gala Yuzawa or even Karuizawa - if conditions are right you could schedule one of these at the last minute and if they're not, you could do something else instead.