Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Feb 01 2024 04:37:53 AWUS01 KWNH 010437 FFGMPD CAZ000-011500- Mesoscale Precipitation Discussion 0043 NWS Weather Prediction Center College Park MD 1137 PM EST Wed Jan 31 2024 Areas affected...Central to Southern California... Concerning...Heavy rainfall...Flash flooding possible Valid 010445Z - 011500Z SUMMARY...Warm conveyor moisture axis is starting to become more progressive. Yet, strong convergence along the axis and favorable orientation to the terrain will support quick hitting moderate to heavy rainfall with 2-4" pose flooding concerns. Widely scattered embedded thunderstorms along/west of the axis may allow for isolated rates up to 1-1.5"/hr posing the highest risk for flashy conditions through 15z.=20 DISCUSSION...GOES-W WV suite denotes stronger core of upper low well to the NW between 130-140W north of 40N; though broad diffluent southwesterly flow and hint of southeast edge of the trof providing some cold air advection aloft steepening lapse rates in a subtle negative tilt to the upper-level trof. This is also supporting eastward propagation of the deep layer moisture stream across the narrowing axis. LPW shows north-south orientation remains directed toward the Santa Cruz range but will shifting quickly southeast along the central CA coast, eventually rounding Cape Conception after 09-10z. Backed sfc to low level flow of 35-50kts quickly veers along the moisture axis to southwest and west in a few dozens of miles supporting very strong moisture convergence and a south to north flux into the terrain.=20 Total moisture of 1.25" and these 35-50kts of flow 500-700 kg/ms IVT generally allowing for broad .25-.33"/hr rates though strongest orographic ascent will support localized .5-.75"/hr rates, with values of .75" occasionally ticking up to 1"/hr as the orientation of the ascent channel becomes nearly orthogonal across the Transverse ranges after 09-15z. HREF 2"/3hrs reaches 40-50% between 12-15z with 85-95% of 3"/6-12hrs across the Transverse range. Given the duration, spots of flash flooding can be considered possible. Current 10.3um EIR loop and local RADAR loops have shown some embedded convective elements near San Francisco Bay, Santa Cruz Mtns into the Northern Santa Lucia Range. These cells appear to be along, just west of the core of deeper moisture but at the eastern edge of steepening lapse rates with CAA aloft in the weak negative tilting mid-level trof. Lingering moisture should be sufficient for some solid moisture flux into the shallow cells and capable of 1-1.5"/hr rates. Duration is likely going to be limited but spots of 1-2" totals in 1-2hrs also pose possible localized flash flooding. Given broad ascent after the warm conveyor moves through, spots of these cores should become more scattered in nature but may still make landfall through early morning/day break maintaining this small scale risk for Central California coast/coastal ranges through 15z as well. GALLINA ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6KURrZBgjhl5agyxmKuGxlFbv5wiahEIW7SQBFPwVFjAnx1Jr7MhHh5njI0q4o0mQfLb= R81nmNkjg6A3t1a-uCkfIkk$ for graphic product... ATTN...WFO...HNX...LOX...MTR...SGX...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 38522146 37692100 36222022 35191933 34931846=20 34751775 34101758 33561797 33651848 33931918=20 33851986 33902041 34372070 35122098 35782150=20 36292198 36772240 37572263 38042304 38502255=20 =20=20=20=20=20=20=20=20=20=20=20=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) .