Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 27 2025 00:47:56 AWUS01 KWNH 270047 FFGMPD UTZ000-IDZ000-ORZ000-270630- Mesoscale Precipitation Discussion 1014 NWS Weather Prediction Center College Park MD 847 PM EDT Tue Aug 26 2025 Areas affected...Southern Idaho...Far Northern Utah...Far Eastern Oregon... Concerning...Heavy rainfall...Flash flooding likely Valid 270045Z - 270630Z SUMMARY...Scattered incidents of localized flash flooding likely to continue through the early overnight period along the northern and eastern sides of larger scale mid-level cyclone. Additional totals of 2"+ possible, especially north and west. DISCUSSION...GOES-W WV suite shows core of large scale mid-level cyclone continues to lift northward and is currently centered in far NE NV with very impressive 150 degree highly diffluent upper-level jet pattern expanding across eastern OR into western MT before entering the core of the 80-90kt 250mb jet over the Northern High Plains. The sharpness of the ridging continues to provide very strong divergence pattern aloft across the Snake River Plain into the Salmon River Range and low level winds have responded, backed and accelerated through the Snake River Valley increasing convergence across southwest ID into the remaining core of greatest unstable air (1000-1250 J/kg of MLCAPE). Strong convective arc of overshooting tops can be seen across Boise/Elmore county extending north. Deep layer moisture to near 1.3-1.4" and 850-700mb winds to 15-20kt per VWP suggest flux will support 1.5-1.75"/hr rates locally. Slow cell motions in the core of the ridge aloft should allow for some duration where localized 1-3" totals are possible, which fits well toward the 90th percentile in recent WoFS run where qualitative assessment suggests maximum totals generally are just below that 90th percentile value and in some fairly close proximity. Given terrain and naturally low FFG values, this provides confidence that localized incidents of flash flooding are likely over the next few hours. Generally, convergence axis is expected to further lift northwest through the Snake Plain into eastern Oregon, though overall rates/totals should reduce out of the core of deepest overall moisture, but still remain a flash flooding risk. Further upstream, the warm conveyor belt and deep southerly moisture surge continues east of the deeper overall mid-level center through western UT into southeast ID, ongoing thunderstorms continue to burst through the cirrus canopy, through overall well of unstable air continues to reduce across UT into E ID/far W WY.=20 Overall trends should be diminishing over the next few hours with that instability/heating loss, but overall moisture and strength of flux convergence will allow for ongoing activity to be efficient (though likely a bit less than the stronger deeper cores further west) spots of additional 1-2" are probable and may induce similar localized incidents of flash flooding through the early overnight period. New thunderstorm activity is possible near/just east of the mid to upper level center as DPVA may locally back winds and tap smaller areas of remaining unmixed unstable air, but should be very isolated across northern UT and just over the border. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_MHlBDhPOkyBWvFdzWaUzeAGghjP6LzZPq54HPJXp5jeifzOQjDTKfVP5h4QadF5xnnc= mCMoB37fK6q0fEY9eu6hgjs$ for graphic product... ATTN...WFO...BOI...MSO...PIH...SLC... ATTN...RFC...PTR...STR...NWC... LAT...LON 45081489 44181284 43351173 42671123 41941113=20 41401174 41431359 42101407 42091623 42561769=20 44071815 44801778 45041678=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .