Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 12 2023 04:48:02 AWUS01 KWNH 120447 FFGMPD MSZ000-LAZ000-ARZ000-TXZ000-121030- Mesoscale Precipitation Discussion 0702 NWS Weather Prediction Center College Park MD 1247 AM EDT Wed Jul 12 2023 Areas affected...Southern Arakasas...Northern Louisiana... Concerning...Heavy rainfall...Flash flooding likely Valid 120445Z - 121030Z SUMMARY...Flash Flooding likely overnight with spots of 5"+ with considerable/life-threatening impacts possible. Intense, slow moving/stationary thunderstorms within a favorable back-building environment. DISCUSSION...A classic warm advection convective complex flash flooding event has a high probability of unfolding through early morning with back-building and training in proximity to compact slow moving shortwave. GOES-WV depicts a well formed shortwave over west-central AR with well defined outflow channel across NE AR into N MS placing the wave and area of concern within the right entrance of 30-40 kt 3H jet streak providing solid ascent and maintenance of the shortwave. Currently the shortwave is elongated from NE to SW with the base rotating through the Red River Basin near SE OK/Texarkana, providing some lift and strengthening of the LLJ. VWP at SHV denotes modest veering through depth, but 850mb flow has increased to 20-25ks orienting quite favorably to the instability axis across NE TX and surface trof across NE LA to SE LA. Isentropic lift across the boundary from the southwest abruptly backs and slows into the 850-700mb trof across west- central to ESE AR also generally aligning with reduced CINH.=20 CIRA LPW denotes enhanced moisture pooled through depth along this axis with upper 70 sfc Tds and low to mid 60s at 850mb, resulting in 2.1-2.4" total PWat values. Given 2000-2500 J/kg of MUCAPE, updraft strength and moisture flux should support very intense rain-fall rates with 2-4"/hr rates possible in the core of downdrafts. 03z HRRR even denoted some 2-2.5" 15-minute totals will become increasingly possible across S AR especially around 08-10z.=20 Proximity to the mid-level shortwave, has reduced mid-level flow, sufficient for evacuation to reduce pulse convection/downdrafts collapsing upon updrafts but only about 10-15kts. In addition, with veered 850-700mb flow of 20-35kts, upstream convergence should support a quite favorable back-building environment from far SE OK along the upwind edge. Additionally, placement of the 500-300 jet outflow, shows some divergence in the flow to suggest, propagation will be southward increasing the angle between the two vectors reducing forward motions overall, for increased duration.=20 Combined with upstream redevelopment, there are strong signals for very high rainfall totals through 12z this morning with the bulk of Hi-Res CAMs supporting 3-6" across the area of concern with some hints of even higher localized totals. 00z HREF 6hr rainfall exceeding 5" are as high as 60-70% across S AR, which could be into northern LA given some spatial uncertainty. As such, flash flooding is going to be likely across much of the MPD area of concern, while confidence is higher than normal for localized significant flash flooding event to unfold through early morning. =20=20=20=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_9ioMhxh5cUZbQ4HF5owu21uierIiXg4-RUxMSu0uqndSahas0jJV597UjtlPnna8Jzc= 5jPfGBZ8kSw0WNikVoK2IcE$ for graphic product... ATTN...WFO...JAN...LZK...SHV... ATTN...RFC...ABRFC...LMRFC...NWC... LAT...LON 34509353 34369211 33879114 32669127 32289191=20 32399312 32739390 33169423 33619425 34199408=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .