Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Apr 20 2024 20:05:04 AWUS01 KWNH 202004 FFGMPD LAZ000-TXZ000-210200- Mesoscale Precipitation Discussion 0166 NWS Weather Prediction Center College Park MD 404 PM EDT Sat Apr 20 2024 Areas affected...South-Central through Eastern Texas Concerning...Heavy rainfall...Flash flooding possible Valid 202003Z - 210200Z Summary...Showers and thunderstorms expanding across portions of eastern Texas this afternoon will intensify through the evening and begin to train to the northeast. Rainfall rates of 1-2"/hr, possibly higher at times, are expected within this strengthening convection. This will result in 2-3" of rain with locally higher amounts up to 5", possibly resulting in instances of flash flooding. Discussion...The regional radar mosaic this afternoon indicates a rapid expansion of showers and thunderstorms across eastern Texas from near the LA/TX border southwest through portions of south-central Texas. Rainfall rates within this fresh convection have been estimated via local WSR-88Ds to be up to 1"/hr already, with regional mesonet observations measuring as much as 1/3 of an inch in 20 minutes. This development is being fueled by a combination of synoptic ascent through increasing upper diffluence in the tail of a 130kt upper jet streak, modest PVA in the vicinity of weak mid-level impulses moving through the flow across TX, and increasingly impressive low-level convergence along the front. Additionally, some isentropic upglide is occurring as the 925-850mb flow surges out of the Gulf of Mexico and atop the stationary boundary. This deep layer ascent is working upon a favorable thermodynamic environment for heavy rain characterized by PWs as high as 1.8", around the 90th% according to the SPC sounding climatology, and MUCAPE above 3000 J/kg. As the afternoon progresses, the high-res guidance is very consistent depicting a strong signal for an expansion of heavy rainfall across this area. Recent runs of the HRRR, ARW, and ARW2 all indicate that an axis of heavy rain will develop along and just north of this stationary front, likely responding to the persistent mesoscale ascent occurring there in the otherwise pronounced synoptic lift. Mean 850-300mb winds are progged to remain progressive at 20-30 kts, but will also be favorable aligned with the Corfidi vectors, suggesting an enhanced training threat as storms build back into the greater instability and lift ENE. With rain rates likely peaking above 2"/hr at times as reflected by both HREF neighborhood probabilities and the HRRR sub-hourly fields, this will likely cause stripes of 2-3" of rain, with locally as much as 5" possible noted by HREF 54"/6hr neighborhood probabilities reaching 20-30%. FFG across the region is quite high at generally 3"/1hr and 4"/3hrs, which is responsible for capping HREF FFG exceedance probabilities at just 20-30%. However, there is an axis of higher 40cm soil moisture noted via NASA SPoRT from just west of Houston up towards the ArkLaTex. While flash flooding is possible in most areas where these heavy rain rates train most efficiently, instances are most likely should the rain fall across these more saturated soils. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7oFb5SqJuy66VOfCVHIoWsFSki2OfVAjAigJTUt4-90q8IXfFtAhqFz1o-iShAueo-5r= NBu25Dceh7xWQMR-E_AjtYU$ for graphic product... ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV... ATTN...RFC...WGRFC...NWC... LAT...LON 31959462 31709384 31169358 30499374 29949427=20 29549529 29079646 28319777 28089802 28039844=20 28229869 28789868 29449846 30149790 30929717=20 31699595=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) .