Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Aug 06 2023 21:20:48 AWUS01 KWNH 062120 FFGMPD MTZ000-WYZ000-IDZ000-070230- Mesoscale Precipitation Discussion 0878 NWS Weather Prediction Center College Park MD 520 PM EDT Sun Aug 06 2023 Areas affected...Central & Eastern ID...Southwest to South-central MT... Northwest WY... Concerning...Heavy rainfall...Flash flooding possible Valid 062120Z - 070230Z SUMMARY...Scattered to numerous above normal intense downdrafts are capable of 1-1.5" in 1-2hrs across complex terrain. Spotty flash flooding is considered possible. DISCUSSION...GOES-E Visible imagery depict scattered to numerous convective anvils across the Intermountain west of central ID, SW MT into NW WY. A remnant MCV in the Boise Range over W central ID is along the eastern edge of the positively tilted mid-level trough starting to swing through OR into SW ID. This is bringing broadly deep layer westerly flow through S ID into S MT/W WY and with it enhanced moisture, though not ideally overlapping through depth as noted in the CIRA LPW. 850-700mb moisture appears to be a bit further north along and north of toward the deeper layer deformation zone (generally in easterly flow); however, this appears to conflict with low 50s Tds in the region. However, an enhanced area of 700-500mb moisture is skirting through the Sawtooth, the Basin-Ranges of SE ID into central WY. Being south of the deformation zone/shear axis, brough near full morning to early afternoon sufficiently raising temps and increasing SBCAPEs across the area of concern. The upper-level shortwave providing modest DPVA (15-30kts from 7 to 500mb) and some weak divergence along the apex of weakly anti-cyclonically curved upper-jet appears to enhanced mountain circulation thunderstorms across much of central ID, SW MT and into NW Ranges of WY. While hail is likely erroneously enhancing rain-rates/totals in the MRMS, spots of .75-1"/hr are probable in these narrow downdrafts. Given the terrain, spots of higher than normal runoff may be inducing flash flooding conditions. MRMS Flash is depicting solid responses for those cells within good RADAR coverage, even if they are slightly enhanced by some hail contamination, this can provide some confidence of those intense rain-fall rates.=20=20 With time, further north and eastward propagation and expansion of thunderstorms is likely to occur, even at the edge of the deeper low level moisture gradient over SW to South-central MT, where weak cyclonic curvature is noted in deeper steering layer. This may enhance a few more minutes of duration of rates and as such, the risk of widely scattered 1-1.5" totals are possible, along with localized flash flooding concerns. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!79-Fo0vmafZa-VByqeH0xhG7duH46pep32e3nhxCV9rzIvOEbRWooxUVCypxcupoDlRu= JxlxBNX_hBIVzUutzi5fv_Y$ for graphic product... ATTN...WFO...BOI...BYZ...MSO...PIH...RIW...TFX... ATTN...RFC...CBRFC...MBRFC...NWRFC...NWC... LAT...LON 46671150 46430953 45680774 44650654 43420685=20 43180906 42821045 42111157 42091339 42551321=20 42901250 43291214 43481223 43551260 43231312=20 43111383 43201480 44181571 46091547 46601380=20 =20=20=20=20=20=20=20=20=20=20=20=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) .