Forecast of the Day • A National Weather Forecasting Contest

Bishop, California ("The Mule Capital of the World") is a town in a a 4000 ft valley just to the east of 14,000 ft peaks of the Sierra Nevada Mountains. Although the Sierras receive a tremendous amount of snow, Bishop only averages 5 inches of precipitation (liquid equivalent) per year. But they received 2 inches in February and now Wednesday could bring a month's worth of rainfall in one day. Let's predict the 24 hr precipitation amount for Bishop and see what happens.

Question: Why does Bishop usually get only a fraction of the precipitation received in the nearby Sierra Nevadas?