Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Feb 04 2024 15:33:25 AWUS01 KWNH 041533 FFGMPD CAZ000-050000- Mesoscale Precipitation Discussion 0046 NWS Weather Prediction Center College Park MD 1032 AM EST Sun Feb 04 2024 Areas affected...Central to Southern CA Concerning...Heavy rainfall...Flash flooding possible Valid 041530Z - 050000Z SUMMARY...A strong atmospheric river continues to overspread central CA, with heavy rainfall expected to continue and gradually shift south down into southern CA later today. Runoff problems and areas of flash flooding will become a concern over the next several hours as rainfall rates continue to increase. DISCUSSION...The latest GOES-W IR satellite imagery shows a strong low center offshore of central CA with an area of deep Pacific moisture and associated rainfall seen continuing to surge off to the northeast and inland across the central CA coastal ranges. The low center continues to deepen and the IVT magnitudes offshore continue to increase around the eastern flank of the low center as very strong low to mid-level southerly flow foster IVT values approaching 1000 kg/m/s. Some of these higher IVT magnitudes will be impacting the Bay Area and especially areas farther south down the coast including the Santa Cruz and Santa Lucia mountains. Already there are offshore rainfall rates on the order of 0.50" to 0.75"/hour as evidenced by recent offshore microwave passes, and the CMORPH2 data shows these heavier rates encroaching on the central CA coastal ranges. Strengthening upslope flow into the windward slopes of the higher terrain will likely enhance these rates further over the next 3 to 6 hours, with some potential for rates to reach 1"/hour occasionally. Strong warm air advection and related IVT will be also be surging inland into the Sacramento Valley and northern portions of the San Joaquin Valley and this will allow for heavier rainfall rates that may occasionally reach a 0.25"/hour to spread across these areas over the next several hours. Farther down the coast, there will be growing concerns for the Transverse Range of southern CA where the moist deeper layer flow and axis of stronger IVT will become increasingly aligned orthogonal to the terrain. This will foster increasingly heavy rainfall rates with a combination of deeper layer forcing/divergent flow aloft ahead of the offshore low center/trough, but also enhanced moisture convergence and orographic ascent. Rainfall rates by early to mid-afternoon across the Transverse Range are forecast to increase easily into the 0.50" to 1"/hour range, with a risk for some convective elements that may yield rainfall rates as high as 1" to 1.25"/hour. Going through 00Z (4PM PST), rainfall totals of 3 to 6 inches are expected for the coastal ranges of central to southern CA, and extending as far south as Santa Barbara and Ventura Counties. This will drive increasing runoff concerns which will include urban and small stream flooding, debris flow/landslide activity, and a threat of flash flooding for any more sensitive burn scar locations. Additionally heavy to significant rainfall, and high-impact flash flooding will be a concern especially after 00Z (4PM PST) for the Transverse Range and areas closer into the Los Angeles Basin, and additional MPDs will be issued accordingly later today to address this. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6rD97VkWMoQFUkoK7_aXQbsS0MGxsZAOBhmrhAUBLf9FdgjY-QSx6QV56_KTgKI2q_oE= IFVBPRJDG6TAKMmYoq1G9Iw$ for graphic product... ATTN...WFO...EKA...HNX...LOX...MTR...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 40392248 39852184 38492151 37772123 36942070=20 36302010 35411972 34931854 34101849 34422057=20 35532140 36372217 37622280 38682351 39622341=20 40242310=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .