Clear Sky Charts are extremely popular with amateur astronomers. They are created by Attilla Danko at cleardarksky.com using data produced by the Canadian Meteorological Center. CMC's numerical weather forecasts are unique because they are specifically designed for astronomers. But they have 763 forecast maps, so it can be a chore to find the one you want. Each Clear Sky Chart, which is based on a specific latitude and longitude, retrieves the colored pixels for that location from the various forecast maps and displays them in a single easy to read chart. Each row represents a different sky condition and each column represents a different hour of the forecast. For more information on how to read the charts, visit the Clear Dark Sky Website (cleardarksky.com).
On the Clear Dark Sky Website, you can view a very helpful list and a color coded map of all non-private charts within 120 miles of Reno. On Widipedia, there is also an interesting encyclopedia entry detailing Attilla Danko's inspiration for developing these graphic interpretations of Allan Rahill's forcasting process.