Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 04 2023 19:19:06 AWUS01 KWNH 041919 FFGMPD WYZ000-IDZ000-050100- Mesoscale Precipitation Discussion 0861 NWS Weather Prediction Center College Park MD 318 PM EDT Fri Aug 04 2023 Areas affected...Southern Idaho...Western Wyoming... Concerning...Heavy rainfall...Flash flooding possible Valid 041920Z - 050100Z SUMMARY...Slow moving intense rainfall with widely scattered 1-1.5" totals across rough terrain possibly inducing localize incidents of flash flooding through the evening hours. DISCUSSION...GOES-E WV suite depicts main larger scale deep layer cyclone starting to slide eastward across the top of the large scale ridge out of MT/WY toward the Dakotas. Upstream, enhanced by yesterday's convection, the old comma head continues to elongate/stretch back across the Northern Intermountain West into the Columbia River Valley, with a core of enhanced vorticity across NE OR across the the southern Boise and Sawtooth mountains of south-central ID. This allows for a corridor of enhanced moisture and low level flow (850-700mb) across the Basin & Range Mtns of far southern ID into Wyoming and Jackson Ranges and further east entering the southwestern influence of the larger scale cyclone. Enhanced 4-6C 700mb Tds and 15-25kts of west to easterly flow within nearly full sun insolation through the morning has resulted in increasingly unstable environment. Localized convergence along the ranges has sprouted narrow but potent up/downdraft cores across SE ID into West central WY. Given LPW of .5" in the 700-500mb layer and totals near .75" rates could peak around 1"/hr. Deep layer steering should allow for potential for one or two repeating cores, but given narrow nature only a few spots may see 2 rounds of the most intense, though totals up to 1.5" are still probable. Given this widely scattered areas of flash flooding are possible especially given rougher terrain. Cloud cover was a bit reduced over the far southern Boise/Sawtooth ranges, that a few deeper thunderstorms were able to develop south of the main deeper layer moisture confluence axis noted with more prolonged/gentler rates throughout the morning. Being along the northward portion of the axis, deep layer steering is a bit more limited closer to the 500mb vorticity center/shear axis, so duration may be a bit longer than south of the Snake River Plain, but may exhaust localized instability a bit faster, though upslope flow from the clearer valley floor, could help too. So there is some uncertainty toward longevity for those cells, but enough for similar widely scattered possible instances of flash flooding, as well. Downstream, winds are slightly faster and have some northward confluence from the mean upper-low's circulation over NE WY, prolific cloud cover has likely limited instability in spots, but a few scattered updrafts where clearing manifested are possible to result in heavier rain. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5YPHp46ZK1p7b6aksef7rBDIHz05uGn5Ocw_rsZjdd-rEHXNF_z-MAFm8v0CSoXa0-0N= 0P0NIqFynwSUZ_VRak3yBNg$ for graphic product... ATTN...WFO...BOI...MSO...PIH...RIW... ATTN...RFC...CBRFC...MBRFC...NWRFC...NWC... LAT...LON 44491536 44461461 44331378 44231303 44271209=20 44321107 44010982 43430869 42980806 42470771=20 42020791 42010938 42021093 42001268 42031461=20 42401476 42701301 43041267 43301296 43221357=20 43201458 43261564 43771604 44241602=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) .