Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 21 2023 22:51:56 AWUS01 KWNH 212251 FFGMPD KSZ000-NEZ000-220350- Mesoscale Precipitation Discussion 1089 NWS Weather Prediction Center College Park MD 651 PM EDT Thu Sep 21 2023 Areas affected...southern NE/northern KS Concerning...Heavy rainfall...Flash flooding possible Valid 212250Z - 220350Z Summary...The expansion of strong to severe thunderstorms will pose a localized risk of flash flooding across portions of northern KS into southern NE over the next 3-5 hours. Rainfall rates of 1-2 in/hr with totals of 2-4 inches (locally higher rates/totals possible) are expected. Discussion...Local radar imagery from KGLD showed a slow moving supercell just west of McCook, NE at 2215Z, located just east of a triple point defined by an effective quasi-stationary front extending ESE from just south of McCook into eastern KS, and a dryline extending SSW from Hitchcock County, NE. The quasi-stationary front was reinforced by scattered convection and rain-cooled air to its north with SPC mesoanalysis data from 22Z indicating 2000-3000 J/kg MLCAPE from southwestern NE into north-central KS along with slightly anomalous PW values of 1.2 to 1.5 inches east of the dryline to the central NE/KS border. Thunderstorms have been attempting to become established within the warm sector over western KS, in the vicinity of I-70, but could be fighting low level inhibition and/or weak subsidence in the wake of a subtle shortwave moving across the central KS/NE border. RAP guidance is forecasting an increase of the 20-30 kt VAD wind sampled 850 mb flow into the into the 40-45 kt range by 01Z just north of the KS/NE border. Increased low level overrunning of the rain-enhanced stationary front and/or outflow boundaries will likely support the maintenance and local expansion of ongoing thunderstorms with potential clustering and evolution toward the east over the next couple of hours. Thunderstorms coverage south of the quasi-stationary front is a bit more uncertain but to the north, the main question for flash flooding will be the speed of storms. A quicker forward progression downstream will obviously limit the flash flood threat but favorable jet divergence/diffluence aloft over southern NE combined with merging and short term training of cells should promote the potential for 1-2 in/hr rainfall rates with localized potential for 2-4 inches (locally higher) through 04Z. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8W_m0w8zIWlSKaQXq_WlTM5GvRWmGF-0G55Da3_GmMjvRt150a4ZTKZWVOUlXpJV_44l= 93dwY1IKo4BfboS0_C2FX-E$ for graphic product... ATTN...WFO...DDC...GID...GLD...ICT...LBF...TOP... ATTN...RFC...MBRFC...NWC... LAT...LON 41289920 41129853 40379805 39669787 38969818=20 38759946 39030014 39450032 39740044 40180111=20 40920050=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) .