Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon May 22 2023 00:12:41 AWUS01 KWNH 220012 FFGMPD MTZ000-IDZ000-ORZ000-WAZ000-220610- Mesoscale Precipitation Discussion 0321 NWS Weather Prediction Center College Park MD 812 PM EDT Sun May 21 2023 Areas affected...eastern WA/OR into western/northern ID and northwestern MT Concerning...Heavy rainfall...Flash flooding possible Valid 220010Z - 220610Z SUMMARY...Increasing coverage of thunderstorms will pose a localized flash flood threat across parts of eastern WA/OR into western/northern ID and northwestern MT. Peak rainfall rates of 1-1.5 in/hr will be possible through 06Z. DISCUSSION...Trends in thunderstorms across the Northwest have shown increasing coverage over the past hour as better ascent nears ahead of a negatively tilted upper trough seen on GOES West water vapor imagery. Through 2330Z, development has been noted over the Blue Mountains and back to the west over Lake County, in addition to a cluster of thunderstorms that has been expanding northeastward over southeastern OR. Also, across northeastern WA, two areas of thunderstorms were ongoing, first along the northern WA/ID border and second between the Okanogan River and Kettle Range. MLCAPE varied from 500-1500 J/kg across the region according to the 23Z SPC mesoanalysis and moisture was fairly anomalous for mid-May with PWAT values ranging from 0.6 to 1.1 inches. As the upper trough continues to edge eastward over the next 2 hours, storm coverage is expected to expand from OR into ID. Additional storm development will be possible from northern ID into northwestern MT ahead of ongoing storms advancing downstream. Storm coverage should expand as upper level divergence and diffluence likely increase over the region ahead of a jet streak over central OR, with recent GOES West DMVs measuring 60-70 kt but forecast by the RAP to increase to near 90 kt overnight. While 30-40 kt of flow at 500 mb should keep individual cells progressive toward the northeast, similarly oriented winds in the 1-2 km layer above the LCL should favor short term training.and repeating of storms over a few areas. Peak rainfall rates near 1 to 1.5 in/hr are expected with storm totals near 2 inches. While coverage is expected to remain isolated, elevated rivers/creaks/streams and above average soil moisture may increase potential for localized flash flooding, in addition to overlap with any recent burn scar regions. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7GV9NPMhqUKhc7_6kjBLzSfQvXhUQwzS8baCayKocg-SI9EMTv0eGgarOhSq7B14mHiB= uoz9BlXQN_jvWAftmUkmX60$ for graphic product... ATTN...WFO...BOI...MSO...OTX...PDT...PIH...TFX... ATTN...RFC...MBRFC...NWRFC...NWC... LAT...LON 49111775 48961469 48451324 47351281 45931322=20 44831454 43371679 42351837 42381933 43251922=20 44441836 45871788 46971716 47551725 47891791=20 47941935 48471947 49071889=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) .