Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Nov 08 2022 05:56:45 AWUS01 KWNH 080556 FFGMPD CAZ000-081500- Mesoscale Precipitation Discussion 1115 NWS Weather Prediction Center College Park MD 1255 AM EST Tue Nov 08 2022 Areas affected...Central California Coastal Ranges... Concerning...Heavy rainfall...Flash flooding possible Valid 080600Z - 081500Z SUMMARY...Scattered shallow thunderstorms along/ahead of sharpening cold front pose localized rates up to .75"/hr and 1.5-2" totals in 1-3 hrs posing possible localized flash flooding risk, especially near recent burn scar/complex terrain. DISCUSSION...GOES-W WV suite depicts a very broad well curved long-wave trof across the eastern Pacific with the center axis of the trof nearing the NW California coast. The primary center near 40.5N126.5W has three distinct shortwave features rotating around it with the most mature starting to lift up and pivot just south of 40N near 125W; while an upstream shortwave is starting to take shape at the right exit/nose of the 130kt 3H jet reaching the base of the longwave at this time. The binary interaction between this pair of shortwaves is allowing for the surface low to dig southeastward helping to build the pivot point of the low to mid-level circulation just offshore of S Mendocino/NW Sonoma county. Broad diffluence aloft as the jet rotates will allow for continued favorable UVVs and promote a tightening of the sfc to boundary layer convergence ahead of the height-falls, increasing low level moisture profiles up to .75" of total PWat ahead of the front. Modest Tds warmer low levels will be over-run by CAA from negative tilting of the larger scale trof aloft will enhance steepening lapse rates and expand the modest 250 J/kg of CAPE analyzed now toward a broader field with 500 to 600 J/kg available through 12z.=20 GOES-W 10.3um animation is already showing some of expanding mid-level cirrus tops of the shallow developing convection along/ahead of the front while GLM has seen a slow uptick in lightning strikes, including cells near Monterrey Bay and points west. It is these cells that will increase in coverage and with increasing low level moisture flux (40-50kts; 80-90 degrees) as the cold front sharpens will increase rainfall efficiency of the cells, slightly more the further south and east with time. As the front makes landfall in the 09 to 12z time, northern less efficient cells will have slower cell motions perhaps even hanging up along southwest facing orography increasing duration, including as far north as coastal Marin/Sonoma county. Stronger cells with capability of .75"/hr rates will be more scattered but more progressive across the southern Santa Cruz mountains and across the Santa Lucia range from 12z to 15/16z reaching southern SLO county. 03z HRRR solutions even suggest rates of .3-.4" in 15 minutes are possible. As such, isolated spot totals of 1.5-2" are possible in the mid-ground between faster moving cells further south and slower less efficient cells north with possible repeating cells...this looks to be around Monterrey Bay from 12-15z. Given the short-term intensity, isolated flash flooding conditions are considered possible, especially in steep, reduced vegetation topography including recent burn scars. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5LiBRLfP9ozYbNcMDk5r3dWrnToCs3z7n2yzCuc1tzO21_nifN7s1MLSPxaVzlvnvHcV= ik8VljTyJcv7-UsdllmFc54$ for graphic product... ATTN...WFO...LOX...MTR... ATTN...RFC...CNRFC...NWC... LAT...LON 38722315 38372283 37962244 37352196 36912140=20 36562101 35952067 35352030 35242065 35312102=20 36022173 36962243 37562266 37822295 38462347=20 38702359=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) .