Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon May 29 2023 01:09:01 AWUS01 KWNH 290108 FFGMPD NEZ000-SDZ000-290545- Mesoscale Precipitation Discussion 0371 NWS Weather Prediction Center College Park MD 908 PM EDT Sun May 28 2023 Areas affected...Southwest to Central SD...Ext Northern NEB... Concerning...Heavy rainfall...Flash flooding possible Valid 290115Z - 290545Z SUMMARY...Deepening thunderstorms along line are slow moving waiting for upstream height-falls/outflow boundary. Potential cell mergers/repeating tracks pose possible 2-3" totals and localized flash flooding. DISCUSSION...Regional RADAR mosaic and GOES-E fading visible imagery denote recent uptick in convective vigor along leading line of convection from Hughes to Mellette before arching west-southwest into the Sand Hills of NW Cherry County. Overshooting tops below -60C and numerous overshooting tops indicate the vigor, likely in response to increasing low level flow/convergence in response to approaching height-falls from the west given continued favorable right entrance outflow channel across west-central SD toward the north-northwest and near the center of the shortwave. The 20-25kts of sfc to 850mb flow is backed enough to intersect the western gradient of deepest moisture while remaining in the instability axis. Moisture flux convergence should support 1.5-1.75"/hr rates along the line.=20 This line is also starting to slow in forward progress, as approaching height-falls/outflow boundary is backing steering flow enough to increase duration, with some of the southern stronger cells oriented favorably to the mean steering to the east-northeast along the SD/NEB line. As such, local spots of 2-3" are possible over the next 2-4 hrs.=20 Upstream, stronger westerly/down-sloping flow enhanced by initial convection is resulting in sufficient convergence to develop new cells along the leading line from Fall River to Bennett county.=20 There is fairly solid forward progression with the new cells, but may align with prior convection and wetter ground conditions, in addition lower FFG values in this area naturally. As the outflow/cells reach the western edge of the leading line, cell mergers will allow for instantaneous uptick for localized sub-hourly rates to support 1-2" totals. Once the outflow/westerly wind surge presses east, the line should propagate quick enough to limit overall rainfall totals crossing into Gregory to Buffalo county (less than 2" totals) which should be below the increasing FFG values, reducing the potential into the early overnight period. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-dpzKyF6_eUAUf-BcfJWXZ8BAPBZvWcPAghwbMRtXjKght8UskDfpmGGGUTCPjnwJFoU= die3Gh3QZX4fbQ3uiTixpys$ for graphic product... ATTN...WFO...ABR...CYS...LBF...UNR... ATTN...RFC...MBRFC...NWC... LAT...LON 44450051 44369979 43859956 43129973 42860037=20 42860167 42710253 42910323 43360318 43680262=20 43850190 44010129=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) .