Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Aug 12 2025 06:47:47 AWUS01 KWNH 120647 FFGMPD TXZ000-OKZ000-121200- Mesoscale Precipitation Discussion 0916 NWS Weather Prediction Center College Park MD 247 AM EDT Tue Aug 12 2025 Areas affected...West/Central Oklahoma into far Northern Texas Concerning...Heavy rainfall...Flash flooding possible Valid 120646Z - 121200Z Summary...Slow moving showers and thunderstorms will move across parts of Oklahoma and Texas through morning. Rainfall rates of 2-3"/hr are likely, which through this slow motion could produce 2-4" of rainfall and instances of flash flooding. Discussion...The GOES-E IR imagery early this morning indicates a new swath of cooling cloud tops north of a large convective complex moving from the Texas Panhandle to along the Red River Valley of the South. This fresh convection is associated with increasing convergence along the nose of a S/SE oriented, but modest, 10-15kt 850mb LLJ measured via regional VWPs and analyzed by the SPC RAP. Despite the modest intensity, this LLJ is favorably transporting robust thermodynamics northward to support this new convection, with PWs above 1.75 inches and MUCAPE exceeding 1000 J/kg. Into these thermodynamics, forcing for ascent is being provided via convergence along the aforementioned nose of this LLJ, but also synoptically downstream of a trough axis kicking slowly eastward from the High Plains, and an embedded shortwave moving into the region through the base of the trough. Additionally, a small but well placed 300mb jet streak over KS is leaving favorable RRQ diffluence to increase deep layer lift. The CAMs are generally struggling with the current increase of convective coverage, so confidence in evolution through morning is somewhat limited. However, there is some evidence in the recent NAM3Km and RRFS of handling this new convection a bit better, so these are used to help gauge the flash flood risk. As the LLJ gradually veers (but with some acceleration immediately downstream of the shortwave) it should continue to resupply favorable thermodynamics to support thunderstorms with heavy rainfall. At the same time, forcing for ascent will persist for several more hours before the LLJ veers too far to the west by morning, suggesting thunderstorms will continue to expand. Rainfall rates within this development should exceed 2"/hr at times as reflected by both HREF and REFS neighborhood probabilities, and with mean 0-6km winds of just 5-10 kts aligned with propagation vectors along the nose of this LLJ, regenerating and training cells with these intense rain rates are likely. Where the most pronounced training occurs, this could result in 2-4" of rainfall as reflected by the HREF/REFS PMM. While there is considerable uncertainty into the placement of this heaviest rainfall due to the lack of model agreement and some interruption of the flow possible from other convective clusters in the vicinity, the EAS probabilities indicate the best threat will be along and just south of this LLJ nose. Regardless of the exact placement, slow moving/backbuilding of these intense rain rates will pose a flash flood risk during the next few hours. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-zBZKlRcWbXq2Q11z1MiHkmTXWqytgupKL_nDayQEDtE3iHItqR-6Xvncg_gWfN5ykiC= LY1VQaGXJEOrJgHBBWDIDJc$ for graphic product... ATTN...WFO...AMA...FWD...LUB...OUN...SJT... ATTN...RFC...FWR...TUA...NWC... LAT...LON 36629994 36309878 35869772 35169699 34549686=20 34049707 33569747 33259812 33199891 33569973=20 33990014 34780031 35420050 36020077 36500118=20 =20=20=20=20=20=20=20=20=20=20=20=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .