Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu May 11 2023 09:38:07 AWUS01 KWNH 110937 FFGMPD MSZ000-LAZ000-ARZ000-TXZ000-111535- Mesoscale Precipitation Discussion 0260 NWS Weather Prediction Center College Park MD 536 AM EDT Thu May 11 2023 Areas affected...Portions of Far Eastern TX...Northern LA...Central/Southern AR Concerning...Heavy rainfall...Flash flooding likely Valid 110935Z - 111535Z SUMMARY...Additional bands of showers and thunderstorms with extreme rainfall rates are expected going through the morning hours. Areas of flash flooding are likely, and some of it may be locally significant. DISCUSSION...The latest GOES-16 proxy visible satellite imagery shows a well-defined and slow-moving mid-level vort center/shortwave trough continuing to slowly drift northeast over the Arklatex region. This energy overnight has been favoring the development of showers and thunderstorms with extreme rainfall rates, and especially over parts of far eastern TX involving Nacogdoches County where MRMS data shows as much as 4 to 6 inches of rain has fallen. Meanwhile, multiple bands of convection also continue impact to impact areas of central and southern AR. A major driver of the activity early this morning is the convergent flow in the 925/700 mb layer around the southern and eastern flanks of the vort center and associated shortwave trough. Additionally, a southerly low-level jet of 30 to 40+ kts is in place and has been strengthening the moisture and instability transport into the region. In fact, the latest RAP analysis shows an impressive amount of instability pooled across eastern TX and much of western and southern LA, with MLCAPE values of 1000 to 2000+ J/kg. Meanwhile, PWs based off regional GPS monitors are upwards of 1.8 to 1.9 inches. Persistent southerly low to mid-level flow is expected to continue this morning up across the broader Lower MS Valley region, and this will favor a sustainable transport of moisture and instability into the southern flank of the aforementioned vort energy to help sustain the convective threat. The 00Z/06Z HREF guidance and several runs of the HRRR insist on the greatest concentration of convection becoming more focused over areas of northwest LA going toward 12Z and then continuing through at least 15Z. Locally very heavy rainfall totals are expected with an environment conducive for extreme rainfall rates (2 to 3+ inches/hour) and back-building/training convective cells. The latest CIRA-ALPW data shows notably robust moisture concentrations through the vertical column, and as mentioned in MPD #258, the 00Z RAOB from KSHV reflects a high wet-bulb freezing level which will favor enhanced rainfall efficiency with warm rain processes being dominant. Additional rainfall amounts of 4 to 6 inches will be possible where the cells locally backbuild and train over the same area. Isolated heavier amounts are possible. The heaviest rains are likely to be over northwest LA overall this morning, but additional heavy rains are expected across parts of central and southern AR as well. Flash flooding will continue to be likely, with locally significant flash flooding possible. The Little Rock and Shreveport metropolitan areas will need to closely monitor these convective trends over the next few hours as there is the potential for high-impact rainfall and flash flooding across these locations. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4fIvSSc595fcU6aSS8vRRPafo_eASHfl0Ctc7WHIK0852k1MhxOXoxtxIwRGDPx325xp= GXNTzVEV_RPZaSnPm5q_33g$ for graphic product... ATTN...WFO...JAN...LCH...LZK...SHV... ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC... LAT...LON 35969244 35459156 34219118 32479123 31289189=20 30919309 31119434 31939497 32909424 34269386=20 35569355=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) .