National Weather Service United States Department of Commerce
NCRFC Flash Flood Guidance (FFG)


Flash Flood Guidance provides an estimate of the amount of rainfall  over a specific area during a given duration of time that is required  to cause small streams to overflow their natural bank. NCRFC issues 1, 3, and 6-Hour guidance products twice daily around  11 a.m. and 9 p.m.  It should be noted that these values are meant to be used only as guidance. Topography and/or urbanization in some areas are also contributing factors to flash flooding.

National Weather Service Weather Forecast Offices (WFOs) use this guidance when issuing flash flood watches and warnings. 

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1-hour FFG Values
3-hour FFG Values
6-hour FFG Values


Gridded Flash Flood Guidance is available as an ArcGIS REST Service

The grids are also displayed on the NWS EDD and the NWS RFC Hourly Precip Viewer.

County Flash Flood Guidance was discontinued on March 31st, 2019.