Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 20 2023 13:57:37 AWUS01 KWNH 201357 FFGMPD TNZ000-KYZ000-ILZ000-MOZ000-ARZ000-201811- Mesoscale Precipitation Discussion 0770 NWS Weather Prediction Center College Park MD 956 AM EDT Thu Jul 20 2023 Areas affected...Far Western KY...Northwest TN...Southern IL...Southeast MO Concerning...Heavy rainfall...Flash flooding likely Valid 201356Z - 201811Z Summary...Showers and thunderstorms are expanding in coverage across southern Missouri this morning. Gradual eastward translation of this activity atop compromised soils will cause additional flash flooding over the next several hours. Discussion...Regional radar mosaic over the last hour depicts an expanding area of showers and thunderstorms with 1-2"/hr rates across southern MO in the vicinity of an east-west stationary front analyzed in the region. This activity remains tied to a pocket of enhanced 925-850 mb moisture convergence impinging along the surface front, beneath an area of enhanced diffluence and right entrance forcing with a 250 mb speed max over IL. The 12z sounding out of SGF in the vicinity of the activity reveals an environment ripe for efficient warm rain production, including a saturated tall-skinny CAPE profile (NCAPE ~.17), 1.87 PWAT (around the 90th percentile), and a warm cloud layer around 12,000 ft. Although some dry westerly flow is noted to the south of the complex, SPC mesoanalysis shows a bullseye of 3000 J/kg MUCAPE and 100 mb mean mixing ratios ~16-18 g/kg downstream of the storms. In all, this should support continued maintenance and expansion of this activity as it moves eastward over the next several hours. Thus, the concern is for this activity to propagate and locally train atop areas which were hit hard from yesterday's extreme rainfall event, particularly atop western KY. Individual CAM guidance from overnight has performed very poorly with placement and coverage of this activity, with recent runs of the HRRR having the best handle (albeit too slow and tries to kill the activity off too quickly), which limits confidence in specifics. However, there is a signal noted in the experimental time-lagged RRFS guidance which shows a 70% chance of 3" of rainfall through 18z across western KY and northern Tennessee. The HREF also shows a 10-15% signal for 10 year ARI exceedance, and 5-10% chance of 100 year ARI exceedence through 18z across western KY and portions of central TN (although this is based on the overnight hi-res whihch has performed poorly). However, given the high degree of saturation from yesterday (1-3 HR FFGs around 1-2"), it would not take much to cause issues going into this afternoon, which makes flash flooding considered likely through the next several hours. Asherman ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4brGmLz9NrzYv2C6sIt5W8s7LF2-usY5K7kjmhGwbYs32VEO515wm2P7HNSVlImTruvd= R3Iy5eDGvdd8nY6fXO5Mw5k$ for graphic product... ATTN...WFO...LMK...LSX...MEG...OHX...PAH...SGF... ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC... LAT...LON 38199146 37868859 37248654 36808602 36108596=20 35588636 35618752 36178911 36409018 36809177=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) .