About the 5-and 7-Day QPFs

The 5-Day Quantitative Precipitation Forecast (QPF) products are created by adding WPC's 6-hour QPFs for Days 1-3 (a total of 12 6-hour periods) to a 48-hour forecast for Days 4-5 prepared by our medium-range forecasters. For the 7-Day QPF, we add to the 5-day product a 48-hour forecast for Days 6-7, which is also prepared by our medium-range forecasters. Both forecasts are created twice per day, once at 09Z and again at 21Z.

Forecasts are valid from the beginning of Day 1 through the end of Day 5 (or 7), with the 21Z issuance offset by 12 hours. For example, a forecast prepared at 12Z September 2, 2012, would be valid for the 120-hour period from 12Z September 2, 2012, through 12Z September 7, 2012. The Day 1-5 forecast prepared at 21Z September 2, 2012, would be valid from 00Z September 3, 2012, through 00Z September 8, 2012.

For the Day 1-7 QPF, a forecast prepared at 12Z September 2, 2012, would be valid for the 168-hour period from 12Z September 2, 2012, through 12Z September 9, 2012. The forecast created at 21Z would be valid from 00Z September 3, 2012 through 00Z September 10, 2012.