Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Feb 03 2025 07:03:14 AWUS01 KWNH 030703 FFGMPD CAZ000-031900- Mesoscale Precipitation Discussion 0016 NWS Weather Prediction Center College Park MD 202 AM EST Mon Feb 03 2025 Areas affected...Northern California Concerning...Heavy rainfall...Flash flooding possible Valid 030702Z - 031900Z SUMMARY...Steady rain will continue into northern California today with localized convergence bands of heavy rain embedded within the broader atmospheric river. Localized rates over 1 inch per hour and flash flooding possible. DISCUSSION...Heavy rain associated with the ongoing atmospheric river will continue through the day today. Just in the past 24 hours, rainfall amounts locally exceeding 6 inches have fallen around and just south of the Redding area. This caused flooding in several areas as noted by the local storm reports. For now the band that caused that flooding around Redding has diminished in intensity. However, many of the ingredients that led to the band's formation remain in place. A stationary front remains in the area acting as a convergence boundary between the colder air to its north and the warmer air and southerly flow to its south. A southerly low level jet from 850 to the surface remains strong moving up the Sacramento Valley, with winds to 40 kts at 850 and 20 kts as noted by several stations in the Sacramento Valley south of the area of rain. This low level jet and the orientation of the terrain are locally enhancing convergence at the northern end of the Sacramento Valley around Redding, as noted by localized increased in the radar reflectivities around that area. Meanwhile, plumes of moisture continue to move into the northern California coast, where their initial uplift by the northern coastal ranges are also responsible for heavier rains. The jet stream remains largely zonal extending hundreds of miles west out into the Pacific. The upper low to the north and the high to the south continue to put the squeeze on the moisture plume, increasing upper level winds and narrowing the moisture into a 100-200 mile wide corridor that is the atmospheric river. During the day today, the upper low helping direct the jet stream will retrograde west. This will begin to reorient the atmospheric river from its current westerly flow to a southwesterly flow. This will allow the atmospheric river to begin to drift southward down the coast, while remaining in place over much of interior northern California. This reorientation may also work to support the low level jet, as the wind flow becomes more parallel with the mountains. HiRes guidance is in agreement that rainfall rates should remain largely steady through the early morning, though again embedded heavier bands remain very possible, especially at the northern end of the Sacramento Valley. Where any bands form, localized flash flooding in addition to the ongoing areal flooding cannot be ruled out. A subtle surface low will approach the coast around 18Z, likely enhancing the rainfall rates area-wide from west to east and could cause additional flooding into the afternoon. Expect another 2-4 inches of rain into the northern Sacramento Valley through 19Z with 1-3 inches of rain expected elsewhere in the highlighted area. Wegman ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7nIjQKs2tSVxxpcQYGLU-voXabZlkuB003nbt11vwnS7sz9ePTpazwWKCbA1blSCz4CG= gVYQhD9XiSdz8mYMgIlR4qQ$ for graphic product... ATTN...WFO...EKA...MFR...REV...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 41912071 41622024 41282032 40912043 40342055=20 39872043 39302035 39182094 39862145 40172184=20 40302233 39802263 39442263 39162262 38912281=20 38832334 38902386 39432391 39712388 40082424=20 40392454 40732441 41102419 41622357 41882317=20 41852176=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .