Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri May 30 2025 21:46:12 AWUS01 KWNH 302144 FFGMPD NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-OHZ000-310343- Mesoscale Precipitation Discussion 0337 NWS Weather Prediction Center College Park MD 543 PM EDT Fri May 30 2025 Areas affected...Portions of the Central Appalachians and the Mid-Atlantic Concerning...Heavy rainfall...Flash flooding likely Valid 302143Z - 310343Z SUMMARY...Heavy rainfall will become more concentrated heading through the evening hours across portions of the central Appalachians while also spreading across the interior of the northern Mid-Atlantic. Some embedded thunderstorm activity will favor enhanced rainfall rates, and scattered areas of flash flooding will become likely this evening. DISCUSSION...The latest GOES-E IR/WV suite shows a very strong shortwave trough amplifying across the OH Valley and into the central Appalachians, with a well-defined comma-head/deformation zone currently seen crossing through southeast OH, northern WV and southwest PA. This is driving a deepening wave of low pressure toward the Mid-Atlantic states, with recent surface observations showing a strengthening low center moving east-northeast across far northern VA to the east of KOKV and northwest of KIAD. A quasi-stationary front is seen oriented east of this low center across northern VA/southern MD and through the Delmarva region. The airmass ahead of this strong shortwave is modestly unstable, with warm-sector MLCAPE values of 500 to 1000 J/kg, but there is nose of elevated instability that is wrapping north of the front and into areas of eastern WV through northern MD and far southern PA. Over the next few hours, this elevated axis of instability will combine with strong DPVA, strengthening isentropic ascent, and a related corridor of enhanced frontogenetical forcing for an axis of heavy rainfall to move east out of the central Appalachians and across the northern Mid-Atlantic. Already radar and satellite imagery shows an axis of heavy rainfall with embedded strong thunderstorms impacting northern WV and southwest PA, with this activity moving east toward the MD/WV Panhandles. Meanwhile, downstream areas near the stationary front and into the warm sector will be seeing convection expand in coverage as better instability and strong shear profiles combine with backing low-level flow/surface convergence for an organized convective threat. The latest hires guidance including the 18Z HREF suite, the HRRR, and the experimental WoFS runs favors northern WV/southern PA and northern MD with the heaviest rainfall this evening with a focus on areas near and to the north of the surface low track. Rainfall amounts across this region of 3 to 4+ inches will be possible. However, areas of central and northern VA and into the Delmarva and eventually southern NJ will see bands of convection capable of producing rainfall rates of 1 to 2 inches/hour, with some spotty 2 to 3+ inch rainfall totals possible here. Scattered areas of flash flooding are likely this evening, and this will include a threat to a few metropolitan areas including Washington, D.C., Baltimore, MD, Harrisburg, PA and Philadelphia, PA. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5C0lO_jdg_3w1ZKljP2pV-cdevq6SnWxhCvmGetT1PpsMfljS_8u3Vm4vzHbyou0kX63= d4tmPAqj5p3M0oErw055jYA$ for graphic product... ATTN...WFO...AKQ...BGM...CTP...LWX...OKX...PBZ...PHI...RLX... ATTN...RFC...RHA...TAR...TIR...NWC... LAT...LON 41187479 40607411 39567443 38427606 38137690=20 38077809 38257902 38997961 39258052 39618097=20 40208093 40677977 40717817 40867657=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) .