Click on the legend for the definitions of the significant flood categories:

View the National Significant Flood Outlook graphic 

NWS River Forecast Centers use the best available forecasts for future precipitation given the constraints of current hydrometeorological science.  The number of hours or days into the future that precipitation amounts can be realistically forecast varies across the United States with seasons and geographic area.  For example, forecast rainfall amounts for hurricanes and large scale weather systems can extend farther into the future than they can for local summer thunderstorms.

The MARFC issues  48 hours of forecast precipitation (QPF) throughout the year.  This QPF is used as input to river forecasts as well as MARFC and National Significant River Flood Outlooks.  Therefore, the daily Significant Flood Outlook
Maps do not account for a full 5 days of QPF over the MARFC forecast area.

5-Day QPF for the United States can be found at Hydrometeorological Prediction Center website.  Use the map below to find QPF at other River Forecast Centers.