Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Sep 24 2023 05:35:18 AWUS01 KWNH 240535 FFGMPD LAZ000-MOZ000-ARZ000-TXZ000-OKZ000-KSZ000-241130- Mesoscale Precipitation Discussion 1100 NWS Weather Prediction Center College Park MD 128 AM EDT Sun Sep 24 2023 Areas affected...eastern OK...west-central AR...far southeast KS...southwest MO...far northeast TX Concerning...Heavy rainfall...Flash flooding likely Valid 240530Z - 241130Z Summary...Additional areas of flash flooding are likely with repeating/training of 1-2"/hr rainfall rates. Locally significant to catastrophic flooding is possible, as additional localized 3-5" totals are expected to partially overlap with areas that have already seen 2-5" of rainfall. Discussion...Deep convective activity continues to proliferate across portions of the Southern Plains into the Lower MS Valley during the early overnight hours, producing strong to severe storms and scattered instances of flash flooding. This convection is occurring within a fairly narrow (but distinct) warm sector, extending just ahead of a slow moving cold front extending from central OK into far southeastern KS. Storms have mainly been cluster in two separate areas, including eastern OK and southwestern MO. More recently, storms have begun forming between the gap and are in the process of attempting to organize into a larger MCS. In the meantime, storms have favored localized repeating and backbuilding, which has lead to 1-2"/hr rainfall rates accumulating to 2-5" totals over the past 3-6 hours. Continued organization of convection is expected through the early morning hours, likely resulting in additional heavy rainfall over areas that have already seen flash flooding, as well as into areas downstream in west-central AR into southeastern OK and the Ark-La-Tex. This convective organization will be supported by a strengthening low-level jet with associated moderate to strong moisture transport, as well via the right-entrance region of a peculiar subtropical jet streak that oriented directly equatorward (steered by a anomalous ridge over northern Mexico and an upper-level low and positively-tilted trough, which includes Post-Tropical Cyclone Ophelia, over the Mid-Atlantic and into the eastern Gulf of Mexico). Otherwise, the mesoscale environment within the aforementioned warm sector is characterized by decreasing (but still significant) ML CAPE of 500-2500 J/kg, PWATs of 1.6-2.2 inches (between the 90th percentile and at or above the max moving average, per surrounding LZK/SGF/OUN sounding climatology), and impressive effective bulk shear of 25-45 kts. The 00z HREF suite is in rather good agreement concerning expected QPF going forward, and is notably much farther south and in line with convective trends relative to the prior (12z) run. This output suggests potential for additional localized amounts of 1-3" over areas that have already seen heavy rainfall and resulting flooding, as well as new localized totals of 3-5" farther downstream into southeastern OK, west-central AR, into the Ark-La-Tex. These totals would suggest relatively high odds (20-40%) of exceeding 10-yr average recurrence interval (ARI), per a 40-km neighborhood probability via the HREF (with the highest probabilities centered near Fort Smith), as well as notable odds (10%) of exceeding 100-yr ARIs over east-central OK (near where the highest rainfall of 3-5" has already occured). This certainly suggests that continued (and new) scattered flash flooding is likely, and some flooding may become rather significant to catastrophic locally (particularly across east-central OK into west-central AR, where the most consistent training of convection may occur). It is also worth noting (and reiterating) that southwest MO has seen a fair amount of flash flooding as well, and the HREF does not seem to be handling that area as well. More recent HRRR runs have handled that convection better, which concerning depict the potential for an additional localized 3-5" across this region (including Springfield) as well. Current convective trends are supportive of this scenario, though (hopefully) realized additional totals will be closer to the 1-3" range as convection gradually becomes a bit more progressive and cold pool dominate. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6CCqm69GXHhAYki-buZ5EA6JeYTgJpcPwrCGAkrmne5kGf1lw8vnpsYNkJJDEpQrw4aM= 1CdG--x9QtKTW0siNlSrKmk$ for graphic product... ATTN...WFO...FWD...LZK...OUN...SGF...SHV...TSA... ATTN...RFC...ABRFC...LMRFC...MBRFC...NWC... LAT...LON 37579411 37579366 37339285 36799208 36349188=20 35719198 35059225 34369283 33869322 33109325=20 32819432 33589536 34599636 35629701 36129626=20 36539564 36959511 37349472=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) .