Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jan 16 2023 04:39:25 AWUS01 KWNH 160439 FFGMPD CAZ000-161345- Mesoscale Precipitation Discussion 0045 NWS Weather Prediction Center College Park MD 1138 PM EST Sun Jan 15 2023 Areas affected...Southern California.... Concerning...Heavy rainfall Valid 160445Z - 161345Z SUMMARY...Atmospheric River of enhanced moisture with IVT values over 750 kg/m/s and occassion rain rates up to .5"/hr. Two to 4" totals likely in west facing terrain. DISCUSSION...The leading edges of atmospheric river have been intersecting the Peninsular Ranges of southern California with leading edge of 700-500mb moisture along strong 50kt+ flow supporting precursory wetting of the soils. GOES-WV imagery and AMV denote strong 130+kt core starting to buckle and amplify and supporting strengthening low level jet upstream. CIRA LPW shows a core of enhanced moisture around 125W starting to lift under the slightly backing 850-700mb flow. Combined with the tightening gradient, flow will increase in these layers toward 30-35kts by 06z nearing the California Bight. This will increase IVT values to 750-800 kg/m/s range, which is quite strong. As the core of the moisture nears the coast, convergence near the warm/cold fronts will increase moisture flux convergence to support .25-.3" mainly along and south of the triple-point of warm/cold front as it slides just south of the Santa Barabara/Ventura county coasts after 06-07z. Durations may be a bit limited due to the forward speed of the front and limit overall totals along the LA Basin and lower slopes but still could pose localized runoff concerns. However, concerns in the Peninsular Ranges will be increasing with ..33-.5"/hr rates expected as the core of the 1.25" total PWAT values and stronger nearly orthogonal flow is ascended after 09z.=20 Given strong warm advection, freezing levels should remain high enough for all but the highest peaks and so given a prolonged duration expected localized totals of 2-4" are possible through 15z. Given the core of the moisture plume is expected to be along and just south of the US/Mexico border, terrain in San Diego county will likely have the greatest risk for heavy rainfall including duration. Soil conditions here are above normal through 40cm depth per NASA SPoRT soil saturation ratios but only about 65-70% unlike points well northwest in Central California which are nearer 100%, so the prolonged duration could be more of a concern with slower but increased stream and river rises. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6xZGimxrudAvFKjDV-Y-EeoTszLshU9NnMSeApQD2r96fYef23XXOGlI3N6IVF03ladN= 9rMzsv7igD7jh_Mo8Tblslg$ for graphic product... ATTN...WFO...LOX...SGX... ATTN...RFC...CNRFC...NWC... LAT...LON 34571867 34531803 34291705 33961666 33221631=20 32551615 32491641 32461687 32471716 33061755=20 33551828 33921900 34081926 34401925=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) .