National Weather Service United States Department of Commerce

Flash Flood Threats in the Southeast and Rockies; Excessive Heat in the Southwest

Flash and small stream flooding threats linger across the southern Rockies Wednesday. Strong thunderstorms with heavy downpours may cause local flash flooding along portions of the Southeast states into Thursday. Excessive heat will continue to impact the southern California mountains and deserts into Arizona and Nevada into Thursday. Read More >

Gridded Flash Flood Guidance (GFFG) provides a general indication of the amount of rainfall necessary to cause small streams to overflow their natural banks. During heavy rainfall, usage of this guidance must involve combination of rainfall that has already occurred plus any additional rainfall that is expected to fall over the same location, not to exceed the guidance duration (example: 1-hr or 3-hr). It should be noted that these GFFG values are based upon estimates of average soil moisture and stream flow conditions over 4km x 4km grids. GFFG values also assume that the rainfall event will be evenly distributed over the guidance duration. Flooding may occur with less rainfall than indicated in areas of very high rainfall intensities, impervious surfaces (urban areas), or steep slopes.

The 1, 3, and 6 Hourly Gridded Flash Flood Guidance is also viewable on NOAAs GIS Integrated Dissemination Program (IDP) web services. Metadata and additional information on the gridded flash flood guidance and other GIS Web Services can be found at the National Weather Service Data as OGC Web Services site .  Flash flood guidance on a national scale, can be found here.