Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Dec 17 2024 03:03:52 AWUS01 KWNH 170303 FFGMPD MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-170830- Mesoscale Precipitation Discussion 1176 NWS Weather Prediction Center College Park MD 1002 PM EST Mon Dec 16 2024 Areas affected...Southern Arkansas...Northwest Mississippi..Adj portionsOK, TX, LA... Concerning...Heavy rainfall...Flash flooding possible Valid 170300Z - 170830Z SUMMARY...The potential for continued back-building of weakening but training showers may present a low-end scattered incident or two of flash flooding through the overnight hours. DISCUSSION...GOES-E WV suite denotes an elongated trough/stream intersection extending from northeast Texas across the Delta Region of the MS River toward the southern Ohio Valley toward the tail end of the more amplified exiting flow across the Lower Great Lakes. GOES-AMVs confirm RAP analysis of this intersection extends the length of the broad right entrance to the 70-90kt 3H jet across the TN/OH valley. A small inflection/wave is highly divergent across NE TX providing the enhanced ascent pattern noted with strong cirrus filaments along the northern edge of the convective clusters across NE TX, AR into N MS/SW TN. The deep unidirectional flow extends back to central TX, where moisture is generally confluent before veering into solid isentropic ascent toward the upper level jet entrance. As such, CIRA LPW and RAP analysis show an enhanced pool of moisture starting to near 1.5" with the vast majority below 850mb. Surface analysis shows defined sagging cold front across AR, that is starting to sharpen, with warm sector southerly flow providing weak but sufficient surface convergence from 5-10kts. Strong convection with some weak QLCS features generally training along the boundary/deep layer moisture interface are fed upstream by pool of 1000-1250 J/kg of MUCAPE before diminishing rapidly toward N MS. Rates of 1.5-1.7"/hr are probable given moisture/unstable air and with training profiles may allow for streaks of 2-3" totals, though eastward along the line will see enhanced southeastward propagation. While soil conditions are fairly dry/generally recepible; they are starting to go a bit dormant and rates may be sufficient for localized pooling/enchained run-off.=20 As such flash flooding is considered possible.=20=20 While upstream convection appears to becoming a bit more fractured due to slightly weaker flow, the upper-level divergence/outflow channel is suggestive/supportive of back-building/isentropic ascent. Additionally, this mid-level wave is supporting some shortwave ridging across SW to south-central AR and backing propagation vectors to be be more northward allowing for greater potential for training cells through the next 4-5 hours. Hi-Res CAMs are inconsistent in the evolution overall convective activity/coverage...given the weakened upstream convergence, but ones that do have stronger convergence do depict a higher potential for training/back-building signal near areas that have already received the higher rainfall resulting in initial flash flooding warning. Confidence is high contingent on the evolution and so the risk for continued flash flooding across Texarkana toward the central LA/AR border is also considered possible through 09z (as signals further diminish through the entire hi-res CAM suite). Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4JL0cz_VHm3h9p4tVjTc76TK83nt1BoJs5dsXu1ORbV9cyx5DbBbMIFhfgvCHAe5i5sJ= CN4gz7US5su4YfGLjs8bzDY$ for graphic product... ATTN...WFO...JAN...LZK...MEG...SHV... ATTN...RFC...ABRFC...LMRFC...NWC... LAT...LON 34649054 34488968 33928946 33409022 33069166=20 32919259 32909333 32849406 33109473 33359479=20 33799453 33989415 34199346 34409209=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) .