Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 18 2023 22:33:01 AWUS01 KWNH 182232 FFGMPD WVZ000-OHZ000-KYZ000-INZ000-190400- Mesoscale Precipitation Discussion 0760 NWS Weather Prediction Center College Park MD 632 PM EDT Tue Jul 18 2023 Areas affected...North-central to Northeast KY...Southern OH...Western WV... Concerning...Heavy rainfall...Flash flooding possible Valid 182230Z - 190400Z SUMMARY...Widely scattered incidents of flash flooding are possible this evening across the central Ohio Valley along and north of the MCS. DISCUSSION...Regional RADAR depicts a mature MCS with well defined bow echo racing across south-central KY and Middle TN into N AL.=20 Goes-Visible imagery and 22z surface obs show the surface front is dropping south across W PA bisecting OH into Southeast IND before flattening back toward OLY/LWV. A very moist/unstable air mass remains trapped between the two dominating features with ample deep layer moisture of 1.8 to 2.2" of TPW from W WV back to the MCV/surface wave near SDF. The trapped air very near the cyclonic book-end has recently rapidly convected with cooling tops below -65C under the strength of moisture convergence. Cells will be capable of 2.5"/hr as the cells slide eastward; this will be generally slower than the mean-flow given small divergence in the 500-1000mb thickness field. Favorable orientation for repeating suggest possible spots of 3-4" over the next few hours is becoming possible across central KY.=20 Downstream...broad west-southwest WAA flow along ahead of the wave, gently intersecting the cold front supporting convergence for scattered thunderstorm development with increased clustering near and east-southwest of the front in S OH, starting to increase in W WV. Upper-level divergence remains strong across the area with favorable anti-cyclonic curvature aloft enhanced by prior MCS activity this morning into afternoon to support further evacuation aloft and efficient updraft maintenance through the early overnight period. While deep layer flow is fairly strong to support forward propagation, sufficient thunderstorm rotation is supporting increased moisture flux and Bunkers right mover propagation vectors suggest a 5-10kt reduction in forward speed with best rotation. Though moisture/instability is less than near the MCV, the cell mode and moisture convergence should support 1.75-2"+/hr rates. Proximity to the cold front will allow for increased opportunity for some repeating. As such, isolated spots of 2-3" are possible, across S OH into W WV, where FFG values are generally lower allowing these totals to trigger possible incidents of flash flooding over the next few hours. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_zl3lHkLqOdXeWprmDbdITHM8ZzxhNJ8zZjjSFyC-VosKD4JuFCrYd2Uw3taNgA463IG= 86kO9xXmn6TgohbWOT6NmMM$ for graphic product... ATTN...WFO...ILN...JKL...LMK...RLX... ATTN...RFC...OHRFC...NWC... LAT...LON 39718334 39628202 39238040 38598060 37948112=20 37458223 37388317 37368450 37408555 37538637=20 37948660 38408632 38728568 38988512 39518438=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) .