Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Aug 06 2023 00:48:02 AWUS01 KWNH 060047 FFGMPD MNZ000-IAZ000-NEZ000-SDZ000-060700- Mesoscale Precipitation Discussion 0875 NWS Weather Prediction Center College Park MD 847 PM EDT Sat Aug 05 2023 Areas affected...Eastern SD...Northeast NEB...Western to Central IA...Far Southwest MN... Concerning...Heavy rainfall...Flash flooding possible Valid 060100Z - 060700Z SUMMARY...Likely continued flash flooding into overnight period across NW IA and near warm sector. Additional spotty areas of possible flash flooding in proximity and east of the upper-low where embedded convective cells would be slow moving or repeating. DISCUSSION...GOES-E suite of imagery shows center of mid to upper stacked cyclone still remains over the center of SD. However, stronger lobes of vorticity are starting to elongate the wave and likely to wobble the system toward the south-southeast in through the overnight period. The western lobe is starting to shift southward and is supporting height-falls across NW NEB starting to press the cold front eastward out of the Sand Hills, it is preceded by another weak wave that has produced a surface trof that extends from YKN to OFK to GRI and south. Solid southerly flow ahead of the boundary continues aid moisture/most unstable air pooling through the Missouri Valley toward the warm front that extends from LRJ to DNS, ADU and south. Very strong moisture convergence has locked that boundary in place and continues to support strong convective development along it, particularly across NW IA where ongoing flash flooding is likely to be exacerbated with upstream redevelopment from aforementioned approaching clustered thunderstorms ahead of the pressure trof. Deep moisture of 1.7-2" remained pooled along and north of the front toward the center of the upper-low through an effective TROWAL in Eastern SD. Instability is likely to diminish slowly with loss of daytime heating, but MLCAPE of 1500-2500 J/kg remains available for stronger thunderstorms likely to merge/congeal along the warm front into the early overnight period. Continued efficient warm cloud rain processes will support 2"/hr rates, that may increase to over 2.5"/hr with cell mergers over W IA. Spots of additional 3-4" are probable through the deep moisture axis/along the warm front likely to maintain flash flooding risk through 06z, while a spot of 5" still remains possible. Further north, elevated instability arcs through the TROWAL in E SD, deep layer flow is a bit more unidirectional limiting best/enhanced convergence. MUCAPE of 500-1000 J/kg may spark scattered to widely scattered embedded thunderstorms, updrafts are likely to be narrower than further south in NEB/IA, but could support localized 1-1.5"/hr rates and it in this slow moving flow regime, isentropic ascent may allow for narrow stripes of back-building resulting in a scatter shot pattern of spot of 2-3" across E SD through 06z. As such, flash flooding is more conditional here and likely to be on the lower end of coverage and intensity in comparison to southward, but a remaining risk nonetheless. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_mIsLOgNPa6YFQ0mh3hDbTpPyDfU0FOh_X8kGULoSYlccJKKo49HX8WpqaCDFthVPCBR= 9b70KVsoJg7fQEB4o1W8hy0$ for graphic product... ATTN...WFO...ABR...DMX...FSD...OAX... ATTN...RFC...MBRFC...NCRFC...NWC... LAT...LON 45049851 44939722 44499635 43589509 42829438=20 41629371 40979494 41189645 42209694 43239759=20 43869888 44499907=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) .