Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Oct 28 2023 04:06:18 AWUS01 KWNH 280406 FFGMPD TXZ000-281005- Mesoscale Precipitation Discussion 1165 NWS Weather Prediction Center College Park MD 1204 AM EDT Sat Oct 28 2023 Areas affected...Portions of North and Central TX Concerning...Heavy rainfall...Flash flooding likely Valid 280405Z - 281005Z Summary...Areas of flash flooding to continue overnight with additional localized totals of 3-5"+ possible (on top of recent estimated rainfall as high as 3-6", locally). Some flash flooding may result in significant to extreme impacts locally (particularly across more urbanized areas). Discussion...Scattered showers and thunderstorms continue across portions of North and Central TX tonight, along a near a slow moving cold front that remains draped across the region. Short term totals in association with the most intense convection have been quite prolific over the past several hours, with MRMS rainfall estimating localized rates of 1-3"/hr. These rates are being achieved through highly efficient warm rain processes, as evident by the 00z FWD sounding which indicated freezing levels of nearly 16k feet (with a nearly saturated column below, per low-level RH of 84%). In addition, the mesoscale environment across the greater region is characterized by MU CAPE of 750-1250 J/kg, precipitable water values of 1.4-2.0 inches (generally between the 90th percentile and max moving average, per FWD sounding climatology), and a zone of low-level frontogenesis/warm air advection (maximized near 925 mb). Scattered areas of flash flooding are ongoing and are likely to continue through early morning, given that 3-6" localized totals have occurred over the past 3-6 hours. In addition, 2-5" totals (with localized higher amounts) have been widespread across the region of the past 2-3 days, so soils remain quite saturated (per NASA SPoRT-LIS 0-40 cm soil moisture at or above the 90th percentile). In addition, streamflows are generally above normal to much above normal, with some at records levels for the day (per USGS streamflow data). With all of that said regarding antecedent conditions, it will not take much additional rainfall to cause significant issues. The 00z HREF depicts a rather concerning picture overnight, suggesting relatively high odds for 3-5"+ additional localized totals (per 40-km neighborhood method with 3" and 5" exceedance probabilities ranging from 20-60% and 10-30%, respectively). The HREF probability matched-mean suggests that localized additional totals are likely to be on the order of 3-5", which would certainly cause additional areas of scattered to numerous flash flooding (and possibly some significant to extreme flash flooding, should these totals coincide with areas that have already recently received 3-6" of rainfall). Hourly runs of the HRRR since 21z have been fairly dispersed with QPF, suggesting anywhere from 1-2" totals to 3-6" totals (depending on the run). The HREF guidance is about equally dispersed, with some members indicating totals closer to the 1-2" range. Even so, these additional totals are enough to exacerbate ongoing flash flooding, though 3-5" additional totals seem more likely (given the ongoing observational trends and highly favorable environment for efficient heavy rainfall). Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!61jAxN41pYYNXCazbAX1qfWfM_KdaQHpzJUAvRUyvs-D0A4_GjnWv1uUl1T5APslHuYD= WSiYpRNPP7gyPSGXHQWb5QA$ for graphic product... ATTN...WFO...FWD...SHV...SJT... ATTN...RFC...LMRFC...WGRFC...NWC... LAT...LON 33379566 32649518 32109566 31059732 31139943=20 32029959 32599850 33109681=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) .