Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Mar 29 2024 23:40:04 AWUS01 KWNH 292340 FFGMPD CAZ000-300920- Mesoscale Precipitation Discussion 0116 NWS Weather Prediction Center College Park MD 739 PM EDT Fri Mar 29 2024 Areas affected...south-central CA coast into the Transverse Ranges Concerning...Heavy rainfall...Flash flooding possible Valid 292338Z - 300920Z Summary...Heavy rain and possible flash flooding will affect portions of the south-central CA coastline into the Transverse Ranges this evening and tonight. Peak hourly rainfall of 0.7 to ~1.0 inches is expected along with 2 to 3 (perhaps a little higher) inches of storm total rainfall through ~09Z. Discussion...Visible satellite imagery from GOES West showed a well-defined cloud pattern depicting a cyclone just off of the north-central CA coast with an occluded/cold front nearing San Francisco Bay at 23Z. Peak hourly rainfall in and around the Santa Cruz Mountains over the past couple of hours has been in the 0.25 to 0.50 inch range. Water vapor imagery showed a closed mid to upper-level low centered about 250 miles to the WNW of SFO with strongly diffluent flow located east and southeast of the low center. The closed low was tracking toward the southeast, helping to keep the occluded/cold front moving along in a fairly progressive fashion but short term heavy rain was still impacting portions of the CA coast. While the progressive nature of the occluded/cold front is expected to continue through the night given no upstream impulses observed on water vapor imagery to indicate stalling or slowing of the front, locally intense short term rainfall rates are still expected for portions of the CA coast into the Transverse Ranges later tonight. Despite some wavering up/down, peak IVT values of 400-500 kg/m/s are likely to remain fairly steady through 09Z along the coast and locations just inland but any instability should remain low (<250 J/kg), lowering convective potential. Nonetheless, strong forcing and low level winds becoming orthogonal to the axis of the Transverse Ranges should favor hourly rainfall totals over 0.5 in/hr at times within the axis of highest IVT, with localized hourly totals near 1 inch possible. Farther north, the duration of heavy rain is expected to be shorter, limiting storm total rainfall into the 1 to 2+ inch range. The Transverse Ranges will see the greatest potential for rainfall totals in the 2 to 3 inch range through 09Z (although spotty totals just over 3 inches may occur) along with the longest duration of 0.5 in/hr rates, perhaps as much as 2-3 hours for any given location within the terrain. The relatively quick addition of 2-3 inches may result in excess runoff for a few locations from the south-central CA coast into the Transverse Ranges with the axis of heavy rain forecast to be located just west the Los Angeles metro at 09Z. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5-IFI0v51ZDhhmCnxtl0R9joyQ_87WXGbDATjXAq5gOX1qbxzb_RBIQlekRRQsHMjIoC= 4R6dDwAOe4QM9cTNUiRhohc$ for graphic product... ATTN...WFO...HNX...LOX...MTR... ATTN...RFC...CNRFC...NWC... LAT...LON 36382169 36312154 35872109 35592066 35482044=20 35282015 35081977 34931948 34821925 34801891=20 34801874 34721844 34361848 34011886 34221964=20 34432071 35292145 36032186 36262184=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .