Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 21 2023 12:27:31 AWUS01 KWNH 211227 FFGMPD IDZ000-ORZ000-WAZ000-211830- Mesoscale Precipitation Discussion 0958 NWS Weather Prediction Center College Park MD 826 AM EDT Mon Aug 21 2023 Areas affected...Eastern Oregon...West-central Idaho... Concerning...Heavy rainfall...Flash flooding likely Valid 211230Z - 211830Z SUMMARY...Sharp/stationary deformation zone with persistent highly anomalous moisture flux and occasional embedded convective elements capable of 1"+/hr. Localized spots of 2-3" are possible through 21z, resulting in flooding and possible localized flashy conditions at times.=20 DISCUSSION...GOES-W WV depicts nearly full transition of Hilary to a classic baroclinic cyclone with impressive baroclinic leaf developing across N CA into Oregon with broad shortwave ridging expanding over the area of concern and expanding anticyclonic cirrus arching through the entrance to the 110+kt 3H Jet along the western US/Canadian boarder. This is providing strong vertical ascent across the region, while the core of deep layer moisture associated with Post T.C. Hilary has been lifting through western NV toward the region. Concurrently, low level flow through the Snake River Valley in ID has backed with 700mb accelerating to over 25kts from the southeast (increasing to 50kts in the next few hours). Low to mid-60s surface Tds and overall total PWats increasing to over 1.3", perhaps as high as 1.5", which would be at or near local record values using surrounding RAOB history but is nearly 5-6 standard deviations from monthly averages. While mid-level temperature profiles are fairly moist adiabatic, there is still some warm air advection to support some weak mid-level unstable air with MUCAPE values near 500 J/kg.=20 Given the strength of moisture flux convergence into the strengthening deformation/frontogenetical band from NW NV to east-central OR into north-central ID, a broad shield of precipitation is forming along the band with KCBX already showing some embedded convective elements along the the upwind edge at this time. Those elements are likely to settle further north but begin to remain relatively stationary with cell motions likely to be along the arch to support training potential. Those small convective cores are likely to support rates up to 1" maybe 1.25"/hr within the broader .25-.33"/hr shield. Given duration of 3-6+ hours, spots of 2-3" are possible. Orographic ascent across the SE facing terrain is a bit more atypical, especially given the deeper moisture that may expose topography/channels/creeks that have not experienced these types of rates and may result in increased mud flows as well. These rates, totals and topography are likely to induce at least highly localized flash flooding conditions through the late morning into early afternoon period.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_AQIjusrB3lqd_TDitGJx0jMTiLdb7Qb3ifwVo0U7uzn94Mb-oCRLdFTriMy-oRySpYY= mJ3AJ9mnGUQOq8MJuvZ7Vvc$ for graphic product... ATTN...WFO...BOI...MSO...OTX...PDT... ATTN...RFC...CNRFC...NWRFC...NWC... LAT...LON 46661518 45811499 45051531 44041616 43251690=20 42681743 42261793 42081855 42241902 43171930=20 44281883 46021727 46641620=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) .