Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Mar 28 2023 08:01:19 AWUS01 KWNH 280801 FFGMPD CAZ000-281700- Mesoscale Precipitation Discussion 0143 NWS Weather Prediction Center College Park MD 400 AM EDT Tue Mar 28 2023 Areas affected...Northwest to Central California Coastal Ranges... Concerning...Heavy rainfall Valid 280800Z - 281700Z SUMMARY...Atmospheric River moisture surge. DISCUSSION...GOES-W WV depicts a well wrapped up deep layer cyclone along 130W west of central Oregon coast that is running anomalously deep for this time of year around 2.5-3 standard deviations. CIRA LPW depicts a limited connection to subtropical moisture northeast of the Hawai'ian chain, but is not as anomalous but still potent given the wind flow/flux potential. Current surface and satellite analysis suggest a subtle warm front has lifted into NW California about to intersect the coastal ranges.=20 Light precipitation has been falling for hours, but now with deeper moisture connection and total Pwats starting to exceed .75" with the nose of 1" values creeping close southeast of Cape Mendocino into the Lost coast. LPW denotes the broad plume about 70-80 degrees narrows in focus to about 40-50nm at the coast (likely to expand with the increasingly confluent/strengthening sfc to 850mb flow (30 to to 60kts). While narrow, this is a good surge supporting IVT values of 500 to max 650 kg/m/s toward a coastal range that is relatively orthogonal to the southwesterly flow.=20 The front is currently propagating eastward, limiting the placement of the direct focus of the core of the plume; however, an amplifying shortwave along the south-southwest edge of the main core of the upper-low is digging. This will allow for a short window of stalled eastward progression in the approaching shortwave ridging with a more north-south orientation to the plume probably through 12z. Then as the height-falls swing in, the southeastward intersection along the coastal range will shift southeastward fairly steadily, limiting the core of the plume duration at a given locale. Surface winds will increase to 35-40kts along with the increasing deeper layer moisture, though terrain orientation may be a bit less favorable (included lower elevations overall) to get the highest rates. This should support ..3"-.4"/hr rates with occasional periods peaking up to .5" in the narrow core across S Mendocino county/N Sonoma county coastal ranges. This may lead to localized totals of 2-3" by 17z. The right edges of the moisture flux should ascend across Marin and even toward the Santa Cruz range toward late morning (13-16z), with .10-25"/hr rates and a follow-up discussion may be required dependent on observational and guidance trends. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!75D1X53FD894ggRN9TLjDPqcgAUGUrKYYAyLscQ-ft7QodKwZsnXi9p-X5cei3Bxo93G= g7thXeL-H7N0XoiwKjCPD_A$ for graphic product... ATTN...WFO...EKA...MTR...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 40912425 40872391 39872323 39192280 38062231=20 37352187 36902205 37162250 37772284 38282333=20 39022388 39722397 40332454 40692441=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) .