Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue May 16 2023 17:41:00 AWUS01 KWNH 161740 FFGMPD VAZ000-WVZ000-OHZ000-KYZ000-162300- Mesoscale Precipitation Discussion 0304 NWS Weather Prediction Center College Park MD 140 PM EDT Tue May 16 2023 Areas affected...Central and Eastern KY...Southern WV... Southwest VA... Concerning...Heavy rainfall...Flash flooding possible Valid 161740Z - 162300Z SUMMARY...Efficient rainfall producing thunderstorms on the cusp of individually exceeding FFG values, but scattered training incidents are probably leading to stripes of 2-3" rainfall totals and possible flash flooding, particularly into early evening as they progress into complex terrain of the central Appalachians. DISCUSSION...GOES-E WV suite depicts an elongated/shearing shortwave(s) feature across the Ohio Valley with favorable right entrance ascent pattern over northern KY. A surface inflection near SDF advances along a warm front where differential heating from cloud cover generally north of the boundary has limited instability, but is starting to increase to 2000-2500 J/kg of SBCAPE across the warm sector in central KY, which is impressive given fairly moist adiabatic lapse rates. TDs in the mid to upper 60s even filtering into the western slopes of the Appalachians resulting in 1.5-1.75" total PWat values available.=20 Solid convergence along the trailing cold front has sparked stronger updrafts supporting moisture load to support 1.5-2"/hr rates. Forward propagation is quick, likely limiting duration for any given up/downdraft, so repeating/training profiles will be required to reach totals to induce flash flooding. Two factors are working favorably for scattered incidents of training and possible flash flooding. The first: the orientation of deep layer flow is becoming more unidirectional and flat from west to east based on WV suite pattern trends as well as VWP suite through the steering layer across KY. The cold front is already starting to flatten to the flow across the upwind edge from Butler to Hart county, but localized cold pools may help for other instances further north near the triple point. The second factor are increasing TCu across the warm sector of southern Central and Eastern KY, where possible weak rotating updrafts may increase isallobaric enhanced moisture flux convergence, resulting in rates up to 2"/hr (though 1-1.5" may fall in less than 30 minutes, per HRRR 15-minute QPF). As such, streaks of 2-3" totals are possible over the next few hours in the area of concern.=20 Hydrologically, soil conditions are drier than normal across central KY and so FFG values are a bit higher and likely harder to be exceeded in all but the longest duration (2.5-3" totals), but as the cell progress eastward after 21z, lower FFG (<1.5/hr or <2/3hr) and more complex terrain should be easier to exceed. This would also be in place across portions of E KY, S WV and SW VA that have seen .5-1" in rainfall from earlier warm frontal thunderstorms. Scattered incidents of flash flooding are more likely over these areas, but are not certain given cell motions remain fast, so multiple rounds are still likely required. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-3oBeJfrULy0fIMuB4ca3uc5e2ibmzWMAIzl_hFD0SY5F16cazHSAMCC_Li8-YQxtJ8q= L7VRT4gf2QQ1ubnmBDpbjp8$ for graphic product... ATTN...WFO...ILN...JKL...LMK...MRX...RLX...RNK... ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC... LAT...LON 38478299 38318144 37958019 37477999 36868026=20 36638104 36688313 36668494 36718597 36858683=20 37358668 37798582 38398421=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) .