


Flash Flood Guidance
Issued by NWS
Issued by NWS
301 AWUS01 KWNH 141826 FFGMPD CAZ000-150015- Mesoscale Precipitation Discussion 1197 NWS Weather Prediction Center College Park MD 224 PM EDT Tue Oct 14 2025 Areas affected...Southern CA Concerning...Heavy rainfall...Flash flooding possible Valid 141824Z - 150015Z SUMMARY...Locally heavy showers and possibly a few thunderstorms will maintain a threat for areal flooding impacts including potential burn scar flash flooding going through early this evening. DISCUSSION...A strong upper-level low and an associated frontal occlusion continues to drop gradually down across southern CA. The latest GOES-W visible and infrared satellite imagery shows the leading edge of the cold front and heavy rainfall continuing to advance through the Los Angeles Basin, with a substantial amount of post-frontal shower activity maintaining pockets of locally heavy rainfall. Rainfall rates with some of the stronger convective elements along the front and also into the southwest-facing slopes of the San Gabriel and San Bernadino Mountains have been upwards of 0.50" to 0.75"/hour, and these rates are likely to be maintained at least for a few more hours as the axis of stronger moisture transport and convergence with the front continues to advance southeastward down the coast with an approach on the Peninsular Range. However, post-frontal instability associated with steepening mid-level lapse rates closer to the upper low will combine with low-level cyclonic flow into the terrain to maintain plenty of shower activity and perhaps a few thunderstorms going through this afternoon and early this evening. Additionally, the stronger dynamics associated with the digging upper-level low and influx of Pacific moisture wrapping northward up into the upslope areas of the southern Sierra Nevada and also the southern parts of the San Joaquin Valley will continue to foster areas of heavy rainfall here which will include a threat for some intense low-top convective showers. The heaviest additional rainfall totals should generally be across parts of the San Gabriel Mountains and especially the San Bernadino Mountains where as much as an additional 2 to 3 inches of rain may fall (below snow line) by this evening. Lowering snow-levels in time will tend to mitigate some of the runoff potential for the highest terrain, but sufficient rainfall over especially the Pacific-facing slopes and into some of the urban areas is expected to maintain concerns through early this evening for areal flooding impacts and some burn scar flash flooding. Rockslides and some localized debris flow activity near and downstream from burn scar locations will continue to be possible. Orrison ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...HNX...LOX...SGX...VEF... ATTN...RFC...RSA...NWC... LAT...LON 36621923 36061849 35241815 34811741 34361675 33991649 33341652 32631664 32571701 32781734 33401770 33651827 33791851 33911881 34061919 34151938 34291957 34441994 35251986 35902019 36312014