Precipitation Maps Explained

Source: Weather Prediction Center

The page linked at Menu > NATL Weather > At-a-Glance shows maps labeled as Excessive Rainfall Forecast and Quantitative Precipitation Forecast. These terms are defined below.

Excessive Rainfall Forecast

Precipitation (generally in the form of rain) of an unusually high rate. Forecasts of Excessive Rainfall issued by the Weather Prediction Center represent the probability that rainfall will exceed flash flood guidance (FFG) within 40 kilometers (25 miles) of a point.

Quantitative Precipitation Forecast

Quantitative Precipitation Forecasts, or QPFs, depict the amount of liquid precipitation expected to fall at a given location in a defined period of time. In the case of snow or ice, QPF represents the amount of liquid that will be measured when the precipitation is melted. Precipitation amounts can vary significantly over short distances, especially when thunderstorms occur, and for this reason QPFs issued by the WPC are defined as the expected "areal average" (on a 20 x 20 km grid) in inches.