About the Day 4-5 and Day 6-7 QPFs

The Day 4-5 and Day 6-7 Quantitative Precipitation Forecast (QPF) products are prepared by our medium-range forecasters twice per day, once at 09Z and again around 21Z.

Forecasts are valid from the beginning of Day 4(6) through the end of Day 5(7), with the 21Z issuance offset by 12 hours. For example, a Day 4-5 forecast prepared at 12Z September 2, 2012, would be valid for the 48 hour period from 12Z September 5, 2012, through 12Z September 7, 2012. The Day 4-5 forecast prepared at 21Z September 2, 2012, would be valid from 00Z September 6, 2012, through 00Z September 8, 2012.

For the Day 6-7 QPF, a forecast prepared at 12Z September 2, 2012, would be valid from 12Z September 7, 2012, through 12Z September 9, 2012. The forecast created at 21Z would be valid from 00Z September 8, 2012, through 00Z September 10, 2012.