Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Oct 28 2023 09:47:26 AWUS01 KWNH 280947 FFGMPD ARZ000-TXZ000-OKZ000-281545- Mesoscale Precipitation Discussion 1166 NWS Weather Prediction Center College Park MD 546 AM EDT Sat Oct 28 2023 Areas affected...portions of northeast TX & the ArkLaTex Concerning...Heavy rainfall...Flash flooding possible Valid 280945Z - 281545Z Summary...Scattered to numerous flash floods likely to continue through morning with issues broadening in scale with time.=20 Additional localized totals of 2-5" expected. Locally significant and life-threatening impacts are likely, particularly east and southwest of Dallas-Forth Worth. Discussion...Convection has become more organized over the past few hours along a stalled front, orienting linearly from west-southwest to east-northeast along the frontal zone east and southwest of the Dallas-Fort Worth metro area, with additional convection trying to fill in farther afield. Localized totals are adding up to as much as 6-12"+ per radar estimates. This has resulted very saturated soils (per NASA SPoRT-LIS 0-40 cm soil moisture at or above the 90th percentile), as well as elevated streamflows (mostly above normal to much above normal, with some at records levels for the day, per USGS streamflow data). Organizing and broadening convection is a significant concern, given the antecedent conditions and ongoing localized hourly rainfall up to 3"/hr (per MRMS estimates). The recent uptick in organization, coverage, and intensity can likely mostly be attributed to the diurnal strengthening in the low-level jet which has had some aid from disturbances aloft moving out of northern Mexico into Texas, providing significant moisture transport, warm-air advection, and associated frontogenesis. Instability remains sufficient for organized convection on the mesoscale, with a sharp gradient of 100-1000 J/kg of ML CAPE (and more broadly available MU CAPE of ~1000 J/kg). Tropospheric moisture remains at significantly elevated levels as well, ranging from 1.5-2.0" (generally between the 90th percentile and max moving average, per FWD sounding climatology). Freezing levels ranging from 15-16k feet allow for ample warm rain processes via collision-coalescence (as the column from 1000-700 mb remains saturated and entirely above 0C). Mesoscale guidance depicts a significant flash flood situation where heavy rain has already fallen, with a broadening reach of flood concerns as convective coverage increases and that convection attains some level of organization. Additional hourly totals to 3" and localized totals to 5" are possible anywhere within the MPD area, which would be most impactful across areas that have already seen 3-12" of rainfall overnight. Scattered to numerous flash floods are likely to continue across the region through mid-morning, with little movement in the frontal zone and slow, gradual weakening of the low-level jet with time (eventually decreasing the moisture transport and associated baroclinic forcing). Locally significant to extreme flash flooding is likely to continue in areas that have already seen notable rainfall -- flash flood emergencies cannot be ruled out -- while new flooding impacts begin to crop up in nearby areas that have had somewhat limited rainfall thus far. Churchill/Roth ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!51wh2OcgbIX_R3xewuzkLFmcQjiEs9FJQ-W2BcdVxf1t5sCsKYZNc9cDv1TGhzSBSQtV= cOUS_p708sZVqrzLimR2JDo$ for graphic product... ATTN...WFO...FWD...LZK...OUN...SHV...TSA... ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC... LAT...LON 34899431 34759374 34379329 32959429 31599667=20 31459694 31279787 31509847 32389827 33479693=20 34509534=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) .