Subj : Flooding Likely SoCal To : All From : Mike Powell Date : Sat Nov 15 2025 08:58:23 AWUS01 KWNH 151010 FFGMPD CAZ000-152209- Mesoscale Precipitation Discussion 1224 NWS Weather Prediction Center College Park MD 510 AM EST Sat Nov 15 2025 Areas affected...portions of southern California Concerning...Heavy rainfall...Flash flooding likely Valid 151009Z - 152209Z Summary...Heavy rainfall will become more likely - especially beginning around the 14Z/6a Pacific timeframe. Rain rates reaching 1 inch/hr are possible with this activity. Flash flood potential will increase - especially across burn scars and other low-lying, urban, and sensitive areas. Discussion...Convection was beginning to deepen and move northward across open waters adjacent to the southern California coastline this morning. This convection was materializing in response to a deep cutoff low centered near 32N, 124.5W that was beginning a slow migration eastward toward the discussion area. On the eastern periphery of this low, a very moist airmass was in place, with PW values ranging from 1 inch near coastal areas to 1.6 inch just offshore. Weak instability and modest forcing for ascent over land areas are limiting factors for heavier rainfall potential in the short-term and toward 14Z or so. Later this morning, a belt of stronger southerly flow at 850mb will develop toward coastal areas extending from the LA Basin southward along the San Diego County coastline. Some of this flow will interact favorably with coastal ranges (particularly the Transverse) to promote an increasing risk of heavier rainfall. Quick moistening is also expected to accompany this flow over those areas. Rain rates should come up in tandem with approaching ascent and orographic lift, and areas of 1 inch/hr rain rates should occur on a more frequent basis. At least a few instances of flash flooding/excessive runoff are expected. Furthermore, these rain rates should occur over local burn scars, prompting dangerous debris flows in some areas. Locally significant impacts will become possible in this regime. Heavy rain potential will persist through at least 2200Z/1p Pacific Time today and beyond as the upstream mid-level wave makes only slow/gradual progress toward land areas. Cook ATTN...WFO...HNX...LOX...PSR...SGX...VEF... ATTN...RFC...RSA...NWC... LAT...LON 35351981 35191853 34841736 34211654 33441614 32791601 32561639 32561714 33101753 33641831 34191949 34552052 35082065 $$ --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (618:250/1) .