Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jan 10 2023 03:34:29 AWUS01 KWNH 100334 FFGMPD CAZ000-100930- Mesoscale Precipitation Discussion 0034 NWS Weather Prediction Center College Park MD 1033 PM EST Mon Jan 09 2023 Areas affected...interior central CA into portions of southern CA Concerning...Heavy rainfall...Flash flooding likely Valid 100332Z - 100930Z Summary...Areas of significant flooding to continue in the short term across the Transverse Ranges with rain rates up to 1 in/hr and an additional 3-5 inches through 09Z. Farther north into the upslope regions of the Sierra Nevada, rain rates occasionally over 0.5 in/hr will continue over the next few hours with an additional 2-3 inches below 6500 ft in elevation. Discussion...Local radar imagery out of southern CA 88Ds showed the highest rainfall intensity as of 0230Z impacting Ventura into Los Angeles counties with peak rates generally between 0.5 and 1 in/hr, though reports of over 1 in/hr have been observed farther west in southern Santa Barbara County earlier in the event. There have been widespread reports of flooding/flash flooding with debris flows, mud and rockslides across the Transverse Ranges and into the San Joaquin Valley and central/southern Sierra Nevada. GOES West water vapor imagery showed a vorticity max crossing the CA coast just north of San Francisco at 0230Z with diffluent/divergent flow over the south-central/southern CA coast, at the nose of a 110 kt speed max near 250 mb sampled by Derived Motion Vectors. Precipitable water values of 1.0 to 1.4 inches were measured by 00Z sounding and GPS data from San Luis Obispo to Los Angeles counties. In the lower levels, 850-700 mb winds were 45-55 kt from the southwest with a strong orographic component, locally increasing rainfall rates into the terrain. Rainfall intensity was being bolstered by weak MLCAPE along the coast up to ~250 J/kg via recent SPC mesoanalysis data. As the cold front, analyzed just west of Point Conception at 02Z, continues to advance southeastward tonight, it is forecast to weaken as the parent shortwave moves inland into downstream ridging and yet another shortwave begins to dominate a few hundred miles west of the central CA coast through 12Z. The result will be a gradual lowering in rainfall intensity over south-central/southern CA as 850-700 mb winds and precipitable water values come down in magnitude. Areas of flooding and flash flooding are expected to remain likely over the next 2-3 hours across the Transverse Ranges with peak rainfall rates of 0.5 to 1.0 in/hr, but with these values lowering to just over 0.5 in/hr at 09Z. Areas of flooding and flash flooding will certainly remain possible from 06-09Z given ongoing soil saturation and flooding. Farther north, peak rates are expected to lower below 0.5 in/hr in the 06-09Z time frame with lowering snow levels to ~6500 ft above sea level by 09Z from the northwest. Flooding will remain possible north of the Transverse Ranges as well although rainfall intensities will be lower there compared to areas of terrain closer to the coast. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8DMgo2OtG9b_MGzTVLWo63l_gAZZPyKTFQ_c6BS6rX328rn9ygfe6tqgi1Lv134EEXlP= zLIVB4d1Or9k5uhaw0DnWhk$ for graphic product... ATTN...WFO...HNX...LOX...SGX...STO...VEF... ATTN...RFC...CNRFC...NWC... LAT...LON 38281995 37881955 37311914 36621865 36111835=20 35911800 35721797 35121815 34861805 34611768=20 34331689 33931661 33471669 33291727 33281800=20 33361891 33531984 34172071 34662092 35132079=20 35342061 35442026 35611983 35861968 36191985=20 36952054 37592054 38032031=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) .