QPF

Quantitative Precipitation Forecast, abbreviated QPF, is a forecast of the amount of liquid precipitation that will accumulate over a defined geographic area and time period. It is typically given for forecast horizons such as 6, 12, 24, 48, or 72 hours and reported in units of millimeters or inches.

QPF is produced by weather forecasting centers using numerical weather prediction models, ensemble forecasts, and data assimilation techniques. Forecasters combine model outputs with observations from radar, satellites, weather stations, and other sensors, often applying calibration and bias correction to improve the accuracy of precipitation totals. Outputs are commonly presented as gridded maps or fields that show predicted precipitation totals across a region.

The primary purpose of QPF is to inform decision making in areas such as flood forecasting, water resource management, agriculture, aviation, and emergency planning. It supports planning for potential hydrological impacts, infrastructure protection, and response coordination. QPF is frequently used in conjunction with qualitative precipitation outlooks and probabilistic forecasts that express the likelihood of exceeding certain thresholds.

Limitations and uncertainties are intrinsic to QPF. Forecast skill declines with longer lead times and over regions with complex terrain or convective storms. Model resolution, biases in precipitation processes, and the transient nature of storms can lead to underestimation or overestimation of totals. Users should consider ensemble or probabilistic products and local climatology to interpret QPF results effectively.

See also: Quantitative precipitation estimation, Numerical weather prediction, Flood forecasting.