Flash Flood Guidance
Issued by NWS
Issued by NWS
856 AWUS01 KWNH 192303 FFGMPD CAZ000-200502- Mesoscale Precipitation Discussion 1035 NWS Weather Prediction Center College Park MD 703 PM EDT Thu Sep 19 2024 Areas affected...a small part of southwestern California Concerning...Heavy rainfall...Flash flooding possible Valid 192302Z - 200502Z Summary...A few slow-moving thunderstorms have developed along coastal ranges north of Santa Barbara. Some of these downpours were falling on sensitive areas from burn scars, potentially promoting excessive runoff. At least a few hours of locally enhanced flash flood potential is expected. Discussion...Abundant sunshine/destabilization beneath a cold upper trough (centered near 34.8N, -121.3W) has fostered scattered thunderstorm development near San Luis Obispo/Santa Barbara county coastal ranges this afternoon. These storms are very slow moving due to weak mid/upper flow beneath the trough. -17C temperatures at 500 hPa was promoting areas of 500-1000 J/kg SBCAPE in vicinity of the storms. Additionally, despite modest PW values (around 0.8 inch), easterly low-level flow was promoting focused upslope/orogarphic lift against the coastal ranges to promote persistent updrafts and slow-moving downpours. Areas of 0.25-0.5 inch/hr rain rates have been estimated per MRMS so far, with areas of rainfall occurring close to sensitive burn scars across the discussion area. Heavy rainfall/flash flood potential will exist in portions of the discussion area through/beyond 05Z per recent model guidance/CAMs. The persistence of this heavy rainfall regime is tied to expected slow movement of the mid/upper low over the area. Isolated areas of 1-1.5 inches are possible in this regime. Cook ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...HNX...LOX...MTR... ATTN...RFC...CNRFC...NWC... LAT...LON 36232039 36071969 35431895 34861847 34621837 34441887 34681960 35212047 36122109