These maps display precipitation vs precipitation return frequency for 24 hour periods. The loop animates the forecasted 6 hour return frequency values. Values below 1 represent the ratio of precipitation vs the 1-year return frequency value. Values above 1 indicate the return frequency in years. For example, if the value is 25, then the precipitation amount equals the 25-year return frequency. (i.e. a 1 in 25 year event). If the value is 0.5, then the precipitation amount is half of the 1-year return frequency. Precipitation frequency values were obtained from the NOAA Atlas 14 dataset (https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_ak.html).
Yesterday through 7 days ago uses APRFC's QPE for precipitation. Today through Day 7 and the 6 hour Loop uses APRFC's QPF.