Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 30 2023 06:01:50 AWUS01 KWNH 300601 FFGMPD MTZ000-IDZ000-WAZ000-301200- Mesoscale Precipitation Discussion 1008 NWS Weather Prediction Center College Park MD 200 AM EDT Wed Aug 30 2023 Areas affected...Portions of Northern WA and Northern ID Concerning...Heavy rainfall...Flash flooding possible Valid 300600Z - 301200Z SUMMARY...Heavy rainfall overnight and into the predawn hours of Wednesday may result in some flash flooding concerns near the more sensitive burn scar locations. DISCUSSION...GOES-W WV suite shows a strong and negatively-tilted upper trough advancing across the Pacific Northwest which is providing an enhanced axis of upper-level divergence and corresponding deep layer ascent across areas of northern WA and northern ID. This forcing coupled with rather anomalous moisture pooled over the region along with at least some very modest instability should favor some expanding areas of heavy rainfall, including some embedded convective elements that may be capable of producing rainfall rates that occasionally reach a 0.50" to 0.75"/hour. The 00Z HREF guidance shows a west/east axis of relatively stronger low-level moisture convergence setting up late in the night and through the early morning hours across northern WA and far northern ID while also coinciding with proximity of a developing 500/700 mb deformation zone, and this should help to yield the potential for locally more concentrated heavy rainfall. Expect there to be locally as much as 2 to 2.5 inches of rain going through the early morning hours where the heaviest rains tend to persist, and also with considerations of where some locally stronger orographics/upslope flow near some of the higher terrain sets up. These rains may result in some localized urban flooding concerns, but generally the flash flood threat will be confined to the more sensitive burn scar locations and especially given some of the occasionally heavier rainfall rates. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6LEuJf6lYlo1S7lI8GfROQ8vMnR0IHij8CBADEy9oxptMWfBF8-N5XAnvN-SlQHzJe7d= nVXZGMwEixbuzcwkSxPNzU4$ for graphic product... ATTN...WFO...MSO...OTX...PDT...SEW... ATTN...RFC...NWRFC...NWC... LAT...LON 49111886 49071734 48791609 48191527 47721507=20 47351519 47111598 47291686 47321840 47012007=20 47412090 48202108 48832050=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) .