Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 27 2025 22:52:54 AWUS01 KWNH 272252 FFGMPD PAZ000-MDZ000-VAZ000-NCZ000-WVZ000-280400- Mesoscale Precipitation Discussion 0534 NWS Weather Prediction Center College Park MD 652 PM EDT Fri Jun 27 2025 Areas affected...Central Appalachians and interior Mid-Atlantic states Concerning...Heavy rainfall...Flash flooding possible Valid 272251Z - 280400Z Summary...Showers and thunderstorms are expected to increase in coverage along a stalled front through this evening. Rainfall rates within this convection will increase to 1-2"/hr, producing 1-3" of rain in just a few hours, with locally higher amounts possible. This rain falling atop saturated soils and sensitive terrain may result in flash flooding. Discussion...The fading GOES-E visible imagery this evening combined with the GLM flash-extent lightning density product indicate that convection is continuing to expand and intensify across the Central Appalachians and Mid-Atlantic. These storms are developing most robustly within areas not worked over by aftn thunderstorms, especially across VA and eastern WV where SBCAPE above 3000 J/kg is sampled by the SPC RAP analysis. This instability is working in tandem with PWs of 1.7 to 1.9 inches, well above the 90th percentile according to the SPC sounding climatology, to support intense rain rates. Into these thermodynamics, ascent is being produced by broad height falls downstream of a longwave trough axis to the west, modestly diffluent 300mb flow, and most impressively by upslope/isentropic ascent of the low-level winds emerging out of the SW. This SW flow is impinging into a stalled back door type cold front, creating an impressive theta-e and instability gradient into which storms are expected to strengthen. During the next few hours, convection over PA/WV should wane in response to nocturnal overturning within a lack of significant bulk shear. However, areas to the south from the Laurel Highlands through the WV Panhandle and into central VA are likely to become the focus for additional development. This is supported by the simulated reflectivity of the CAMs, including recent HRRR and RRFS runs. These solutions are favored as the evolution matches the conceptual model for the next several hours, with storms developing along the front and any outflows/mergers, and then tracking slowly along the aforementioned gradients. With rain rates expected to peak above 2"/hr (15-25% chance) and 15-min rainfall peaking above 0.75" according to the HRRR, slow and chaotic storm motions of just around 5 kts could result in 1-3" of rainfall with locally higher totals. This region has experienced well above normal rainfall the past 10 days, as evidenced by AHPS rainfall departures that are in some places 150-300% of normal. This has produced widespread 0-40cm soil moisture above the 95th percentile, further compromising FFG below the natural sensitivity of the region due to terrain. This further reflects the concern through early tonight as slow moving torrential rain rates result in rapid runoff and potential instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7o1o6Sm_X2AtsGzhseKab0cgQ5SlAV01Qg54KovfYKg9zmCIiRgVDzT9IatSxH--d9Bh= rj6Kj4Kg_GiOwka4BZIkcoc$ for graphic product... ATTN...WFO...AKQ...CTP...LWX...PBZ...RAH...RLX...RNK... ATTN...RFC...ALR...RHA...TIR...NWC... LAT...LON 41497931 41257868 40247835 39277838 38087830=20 37487817 36857828 36537863 36617936 37008018=20 37668078 38748089 39978071 41068002=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) .