How reliable is the weather forecast?

Weather Forecasts: Just How Reliable Are They? is a nice article about weather forecasts and their reliability. Sounds easy, but what constitutes 'reliable' in the context of a next-day, 5-day, or 10-day weather forecast? You can read the details yourself, but here are the main numbers: next-day 95%, 5-day 77%, and 10-day...well, not so much.