Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Apr 16 2024 03:24:16 AWUS01 KWNH 160324 FFGMPD SDZ000-160730- Mesoscale Precipitation Discussion 0156...Corrected NWS Weather Prediction Center College Park MD 1123 PM EDT Mon Apr 15 2024 Corrected for Resent for spelling errors Areas affected...Western to South-central South Dakota... Concerning...Heavy rainfall...Flash flooding possible Valid 160250Z - 160730Z SUMMARY...Very high moisture flux over outflow boundary is resulting in efficient rainfall production and with slow forward propagation may pose higher rainfall totals (2-3") capable of inducing localized incident(s) of flash flooding. DISCUSSION...Rapid surface cyclogenesis is occurring just south of the Black Hills of SD where a 989mb low was noted. Very strong isallobaric wind response is generating very high southeasterly and easterly confluent low level flow across the central Plains into SDak. Upon this, moisture has been channeled into a tongue across northeast NEB angled into western NEB. Given surface winds of 30-35kts and 850mb flow and winds at the boundary layer of 50-60kts, moisture flux has been very strong. Initial rounds of thunderstorms generated cold pools from drier mid-level air in place subsequently resulting in favorably oriented outflow boundaries to the flow to support additional rapid convective development along the isentropic ascent. Combined with natural low level barrier in the Black Hills low level winds remain highly convergent resulting in sufficient moisture flux into the developing storms for fairly efficient rainfall production (updraft loading) given the overall drier environment. While UDX RADAR suggests modest hail generation, KDP field also supports downdrafts with fairly decent rainfall generation while supporting 1.5-2"/hr estimates. Forward propagation should be effective in eastward cell motions, but current trends suggest stronger mid to upper level divergence channel toward the northwest and north is supporting downshear updraft columns maintaining a bit longer duration for heavier rainfall to accumulate before the outflow boundary presses too far east and generates another updraft cycle further west. As such, north/south oriented lines of enhanced rainfall should be expected over the next few hours with slow eastward advancement before approaching shortwave from the southeast triggers a stronger complex further upstream robbing the best environmental moisture flux. As such a few lines of 2-3" totals are possible over the next 3-4hrs slowly advancing eastward into central SDak. While the soils have been dry, the shear magnitude of rainfall and naturally lower FFG values north of the Sand Hills, suggest these 2-3" totals in 1-3hrs may induce a localized flash flooding incident or two through 08z and considered possible. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5YsR6e8afWLcWAKUFqm9A_6WK_tSFUNhJe5tiL-ljbVq6qVb0xSQQkQolkEtrNaLqnA8= yLJQImVnOAgKPP1eA--9iv8$ for graphic product... ATTN...WFO...ABR...UNR... ATTN...RFC...MBRFC...NWC... LAT...LON 45210237 45080119 44099989 43499991 43290028=20 43370099 43720166 43600249 43340304 43470358=20 44050378 44830337=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .