How accurate are 10-day weather forecasts?

[tizim]

I'm going snowboarding in 10 days or so, and according to the 10-day forecast for Lake Tahoe, there won't be any snow for quite a while.

I remember hearing somewhere that weather forecasts past a certain number of days are 100% completely inaccurate. Does this mean there's still a chance for snow/powder? Anyone know the real deal on weather forecasts?