This type of activity happens every 20-50 years.The Sawtooth Avalanche Center has issued an avalanche warning for the Sun Valley are today. They say the threat is so high, people are being urged to stay away from avalanche terrain.

If an avalanche occurs, officials say they can be bigger and go farther then they have in decades.

Sun Valley Resort has announced that Bald Mountain will be closed until further notice, but Dollar Mountain is open today for skiing and riding.

The avalanche warning will remain in effect until 7a on Friday.