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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

County Flash Flood Guidance averages rainfall over 1,3, and 6 hour duration required to initiate flooding along small streams in the indicated county. These estimates are based on gridded flash flood guidance averaged over each county and current soil moisture conditions computed by River Forecast Centers. Typically less rainfall is required to produce flash flooding in urban areas.