Maryland One important aspect of forecasting a precipitation event is being able to predict in what form the precipitation will fall. Rain storms can cause massive flooding, while heavy snow disrupts schools, transportation, and communication.
Ice storms are a major concern to utility companies and the aviation industry.
The knowledge of what type of precipitation will fall is vital to those who must plan how to handle an upcoming storm and issue warnings to the public. The NGM-based MOS guidance is available in alphanumeric form for over 600 stations in the contiguous U.S. and Alaska. The AVN-based PoPT guidance will be analogous to the current operational NGM product, but the new system will produce forecasts valid every 3 hours from 6 to 72 hours after the 0000 and 1200 UTC AVN model runs, and PoPT guidance will be disseminated for approximately 1000 stations throughout the United States. TDL plans to implement this guidance in late 1999. In this talk, we focus on the development of the PoPT forecast system, including a discussion of the developmental sample, the definition of the predictands, the method of equation development, and the selection of predictors.