Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 27 2023 21:00:40 AWUS01 KWNH 272100 FFGMPD NVZ000-CAZ000-ORZ000-280245- Mesoscale Precipitation Discussion 0358 NWS Weather Prediction Center College Park MD 500 PM EDT Sat May 27 2023 Areas affected...Northern CA...Northwest NV... Concerning...Heavy rainfall...Flash flooding possible Valid 272100Z - 280245Z SUMMARY...Favorable upper-level pattern supports back-building/redeveloping thunderstorms. Atypically intense rain-rates and potential for repeating through the afternoon/evening suggest localized flash flooding may be possible. DISCUSSION...GOES-W WV suite and RAP analysis denote an exiting vorticity center over SW ID slowly sliding east-northeast, while a mature compact closed low sits west of the mouth of the Columbia River dropping south. This leaves the area of concern within a region of favorable shortwave ridging/diffluence aloft for favorable broad scale ascent pattern. At the surface, atypically higher moisture has filtered through the northern Sacramento Valley into the the higher terrain/plateaus of N CA/NW VA with Tds in the low to mid-40s. Steep but also fairly moist mid-level profile are supporting unstable airmass with 500-1000 MLCAPEs across the area of concern. Destabilization and convective development has already started along the Trinity Range ridge and through the Northern Sierra Nevada and across the NW Basin and Range of NV. Deep aatfairly unidirectional flow is supporting some potential for some repeating in the short-term. Though rates are likely to be .5"/hr initially.=20=20 CIRA LPW denotes a ribbon of enhanced moisture from 850-500mb sliding through NW CA at the leading edge of DPVA from the digging compact low to the north. This upstream forcing is expected to maintain, while deeper layer moisture flux will enhance rainfall efficiency through the late afternoon, particularly further west across N CA. Steering flow should also slacken with some potential of low-level (850-700) cyclongenesis while still allowing favorable up-slope flow out of the valley for filtered additional low level moisture. Incidents of thunderstorms with ..75"/hr rates and slow motions suggests localized but scattered 1-1.5"/hr rates. As such, localized flash flooding is considered possible, especially if thunderstorms occur in complex, steep terrain.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!94jLdcseIWDCuPbMsC7bx88Y-fM9ttMldHHx8dxybN6qYotHgvY0rof00pY30J2hZGfo= fJHu6-OE5o5TYCG3HLK3SlQ$ for graphic product... ATTN...WFO...EKA...LKN...MFR...REV...STO... ATTN...RFC...CNRFC...NWRFC...NWC... LAT...LON 42362143 42041952 41431848 40461808 39551939=20 39602044 40172144 40532234 40662265 40892308=20 41442326 42082298=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) .