Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Nov 13 2025 21:36:24 AWUS01 KWNH 132136 FFGMPD CAZ000-140900- Mesoscale Precipitation Discussion 1222 NWS Weather Prediction Center College Park MD 435 PM EST Thu Nov 13 2025 Areas affected...western Transverse Ranges into central CA and northern Sierra Nevada Concerning...Heavy rainfall...Flash flooding possible Valid 132133Z - 140900Z Summary...Flash Flood potential will extend into the evening and overnight hours from portions of the northern Sierra Nevada into much of central CA and the western Transverse Ranges. Peak hourly rainfall of 0.5 to near 1.0 inches is expected along with peak 12 hour rainfall values of 2 to 4 inches through 09Z. Discussion...21Z radar imagery and GOES West infrared satellite imagery showed a band of moderate to heavy rain extending from Monterey Bay and the northern Santa Lucia Range into the eastern Pacific, out ahead of a Pacific cold front. The cold front has been steadily advancing east since this morning and was preceded by an atmospheric river containing max PW values of 1.3 to 1.5 inches along the coast and just offshore. Within this plume were S to SSW 850-700 mb winds of 40 to 50+ kt, supporting earlier hourly rainfall of 0.7 to near 1 inch across the Santa Cruz Mountains. A number of reports of flooding and debris flows have been observed since earlier this morning, in and around the San Francisco Bay region down to Monterey Bay. As a closed low centered near 41N 128W and southward extending trough/low, as seen on water vapor imagery, continues to advance closer to the coast, some weakening of the mid-level low is expected as the system continues to mature and evolve. The cold front will maintain a slow but steady movement toward the east but a ~10 kt weakening of the 850-700 mb winds is expected as the moisture axis advances downstream ahead of the cold front. This weakening will correspond to a lowering of IVT values over land, maxing out in the 600-800 kg/m/s range through 09Z Friday. Occasional peak hourly rainfall of 0.5 to ~1 inch is expected to be focused within locations where low level winds will focus into S to SW facing terrain. The most likely locations for these higher rates will be within the Coastal Ranges and Sierra Nevada but any slowing/stalling of a band of weak convection across the San Joaquin Valley will also have the potential to produce these higher rates given the moisture already present and weak MLCAPE up to 500 J/kg forecast by the RAP. Most instances of flooding/flash flooding are expected to be minor, but will be most probable across urban and other flood prone locations. However, localized occurrences of more impactful flash flooding will be possible where overlap of heavy rain occurs with any sensitive burn scars and terrain with potential for debris flows. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6vhVfx5PrvXg1YFxrXbaLnPzE8TiC_lEuN1IOc2Kw_1rXYSFvDpdUCX5jP9z4cFbAig2= v04FN10JYa31QCEWqszhT5M$ for graphic product... ATTN...WFO...HNX...LOX...MTR...REV...STO... ATTN...RFC...RSA...NWC... LAT...LON 40682176 40442144 39982074 39642050 39382033=20 39082023 38842014 38692005 38551994 38481986=20 38361970 38241972 38131973 38081971 37921946=20 37821936 37701937 37601929 37511915 37431904=20 37151884 36991877 36861884 36661952 36832010=20 36462052 35822041 35232021 34941972 34421932=20 34271951 34302044 34462098 35252146 35842184=20 36472222 37032175 38842141 40302192=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .