Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Dec 26 2024 18:57:14 AWUS01 KWNH 261856 FFGMPD LAZ000-ARZ000-TXZ000-OKZ000-270100- Mesoscale Precipitation Discussion 1193 NWS Weather Prediction Center College Park MD 156 PM EST Thu Dec 26 2024 Areas affected...Northeast TX...Southeast OK...Far Southwest AR... Concerning...Heavy rainfall...Flash flooding possible Valid 261900Z - 270100Z SUMMARY...Reducing instability, rainfall efficiency; but slower moving cells with some training pose spots of 2-3" and widely scattered possible flash flooding through evening. DISCUSSION...The window for excessive rainfall inducing localized flash flooding is starting to close due to multiple factors; one being convection moving into areas of higher FFG, though still equally saturated in the 0-40 cm layer with NASA Sport RSM still in the 60-70% range. The second is reducing moisture flux and available instability. Yet, a training steering profile still remains as well as potential for stationary cells near the pivoting deep layer cyclone over Northern Texas toward 00z. Currently, regional RADAR mosaic and GOES-E suite of imagery show the decaying convection along the effective 850-700mb warm front across NW LA/SW AR angling back to the developing deep layer pivot of the cyclone over the central Red River Valley between North and Northwest Texas. Strong height-falls as the upper-level jet and 5H trough swing more negative tilt across central to northeast Texas; the effective 850mb cold front is aligning to the surface and is pressing much faster eastward to the south. A mid-level dry slot/descent channel is starting to pinch in proximity to Falls, Robertson and Bell county and the LLJ is starting to take a more branched appearance as the confluent flow increases convective activity along the trailing convergent southwesterly flow and effectively severs the best deep layer moisture transport along and ahead of the effective 850mb advancing front.=20 Currently, the window is still open and MUCAPE values 750 J/kg nosing toward 1000 J/kg are still within access and ascend through the western branch of the TROWAL to maintain/promote convective activity across the Heart of Texas region. The southerly backing 30kt flow is supporting 1.25" total PWats mainly below 700mb to providing solid flux convergence for efficient rainfall production for the next few hours with rates of 1-1.25" slowly diminishing with time. Deep layer steering at the nose/left rotor of the developing dry slot may allow for cells to angle sufficiently for some short-term SW to NE training from Freestone/Navarro county region to Red River/Cass counties over the next 4-6 hours. As the dry slot severs the connection rates will drop below 1"/hr and overall totals will reduce to less than the rising FFG values in far NE TX, reducing the potential for low-end flash flooding conditions. A secondary risk may start to occur near the pivot of the deep layer cyclone as it crosses North Texas toward 00z. Steepening lapse rates and remaining modest pooled moisture and convergent flow along the southeast quadrant may spark a few narrow core convective cells. Deep layer steering will be near zero near the center of the low, allowing for Subtle Heavy Rainfall Signature (SHaRS) events with 1-1.5"/hr rates falling over areas having recently experienced prolonged moderate shield precipitation across the Red River Valley and across into S OK. These would be very spotty in nature, but the intensity of the rates in such a small area could pose a localized flash flooding risk as well. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6UeAJSEdlBDof7NCT1FAGCfMmd71AcYjg4AgLFxxQkSypyZ3Uumopuv5xMQCBmxZvgts= T2blZsW2fz5MmAwGwxQv8HU$ for graphic product... ATTN...WFO...FWD...OUN...SHV...TSA... ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC... LAT...LON 34419525 34109433 33619364 32979395 32289460=20 31229645 32409692 33729715 34299646=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) .