Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue May 13 2025 19:45:02 AWUS01 KWNH 131944 FFGMPD PAZ000-MDZ000-VAZ000-WVZ000-140100- Mesoscale Precipitation Discussion 0265 NWS Weather Prediction Center College Park MD 343 PM EDT Tue May 13 2025 Areas affected...South-central PA...Western MD...Eastern WV...Far Northwest VA... Concerning...Heavy rainfall...Flash flooding likely Valid 131945Z - 140100Z SUMMARY...Continued moderate rainfall with occasional weak embedded convective elements within strong orthogonal upslope ascent regime. Localized spots of additional 1.5-2.5" totals possible within broader .5-1" average by early overnight. DISCUSSION...A strong moist dynamic environment across the Allegheny section of the larger Allegheny Plateau in far NE WV, W MD into south-central PA is expected to persist through the evening with a very slow south to north advancement along the ridge lines. Highly anomalous warm conveyor belt with nearly all CIRA LPW layers at or above the 95th percentiles with maxima at the lowest sfc-850. Combine this with persistent, nearly orthogonal 35-40kts of 925-700mb winds per VWP is resulting in IVT values over 600-700 kg/m/s even without support of increased vertical potential from insolation. As a result localized totals have already been over 2-4" throughout the day in E WV/W MD and starting to reach 2-3" across Somerset county in PA. Slightly lower vertical exposure across the Blue Ridge, still spots of 1.5-2.5" have been observed. Additional rainfall will compound and expand ongoing flooding concerns through the complex terrain through 00z. GOES-E WV suite shows broad closed low across the Ohio Valley, though an eastward extension of the low/vorticity maxima is lifting across SW VA/S WV at this time, surface winds are backing in response to the height-falls and the 850mb trof is sharpening increasing directional convergence from more westerly return flow intersecting the 30-40kt WCB flow. Additionally, best diffluent region of the upper-level jet is starting to lift northward ahead of the 850mb trof with apex of the split along the Allegheny ridge as noted in the broad cirrus shield (starting to evacuate Northern VA/E WV. While there will be some insolation, the timing is likely limited across and north of I-64; with strong instability gradient noted in RAP analysis. Still, with the DPVA approaching and some temps rebounding into the low to mid-70s, modified sounding across central VA would support 500-1000 J/kg of MLCAPE that could be utilized in further ascent on the 850mb convergence line. Upstream convection along Albemarle/Augusta can be seen developing in this instability axis and with 700-500mb flow veered a bit, the cells should track NNW into the most affected areas with localized enhancements to the WCB moisture flux to support ..5-1"/hr rates for embedded convective elements through the complex terrain. Rapid refresh guidance (HRRR/RRFS/WoFS) are inconsistent in placement, as expected, but continues to support those embedded additional 1.5-2.5" totals within a broader field of .5-1" totals, likely to maintain on going flooding, slowly expanding coverage northward of flooding risk through the early overnight period. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7JuH7uIBN6Hk4gtCv49xg0SFGrGWdlXSzPyAf3UafcT3ldJyuLUcVihS8kR9-UGT6qGG= pEfuEAU1HlG0B0IGqmo0Gtg$ for graphic product... ATTN...WFO...CTP...LWX...PBZ...RLX... ATTN...RFC...MARFC...OHRFC...NWC... LAT...LON 41277830 41187740 40827691 40267683 38947785=20 38107867 38167922 38757974 39667966 40617905=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .