Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 27 2025 16:52:18 AWUS01 KWNH 271652 FFGMPD PAZ000-MDZ000-VAZ000-WVZ000-272300- Mesoscale Precipitation Discussion 0527 NWS Weather Prediction Center College Park MD 1251 PM EDT Fri Jun 27 2025 Areas affected...Eastern WV...Western and Northwestern VA...Western PA...Far Western MD... Concerning...Heavy rainfall...Flash flooding likely Valid 271700Z - 272300Z SUMMARY...Incidents of flash flooding, potentially significant, are likely to increase over the next few hours in complex/steep terrain.=20 DISCUSSION...GOES-E Visible imagery shows well defined CAD due to back-door cold front dropping through the Mid-Atlantic this morning. The cold front has pressed to just south of the VA/NC boarder and has banked up through the Blue Ridge toward the Eastern Continental Divide Ridge in the wind field but the stratus deck leaves about 25-50 miles of gap of clearing with strong Td gradient even a few more miles further into the stratus deck. As such, surface Tds to low to mid-70s are pooled along the front from SW NY across W PA into the central Appalachian Range. As further insolation occurs temperatures are rising into the low to mid-80s and modified (deeply saturated) 12z RAOB profiles from PBZ and RAP suggest solid MLCAPEs of 2000 J/kg are probable toward peak in the next hour or two even with a narrow-skinny profile.=20 Total moisture profiles remain above normal in the 1.75-2" range.=20 Upstream, the tail end of enhanced moisture and low-level southwesterly speed max provided enough ascent to break out a cluster of thunderstorms which is starting to develop southward into SE OH; this is a timing of enhanced upslope flow from the west with increased moisture/higher theta-E air downstream of the main upper-level trof over the Great Lakes. This will combine with strengthening upslope flow from the moist post-frontal 'cold' air damming (CAD) further strengthening moisture flux convergence to break out scattered to numerous thunderstorms across W PA toward E WV/NW VA. This is likely to persist throughout the afternoon into evening given upstream trof strength and approaching height-falls. So while deep layer steering may lead to eastward propagation into the stable air across central PA into the Capital District region, favorable upstream redevelopment/flanking line support is probable for multiple up/downdraft cycles with main motions driven by cold pools/outflow likely southward into west-central VA/SE WV through the evening hours. Total deep layer moisture, strong updraft/unstable environment will support solid flux to support 2"/hr rates and given the aforementioned motions this may support localized totals of 2-4" in short-duration. Given complex cell motions and shear rainfall intensity expected, an incident or two of considerable to significant flash flooding is plausible as well. Given naturally lower FFG values due to complex terrain, flash flooding is considered likely; yet, recent heavy rainfall will further limit infiltration to the saturated deeper soil profiles, especially in SW PA where 0-40cm soil moisture remains well into the 90th percentile.=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6tCpTMK-blfFSlmSnb5X2ivIL_Eei3kCEC7Y139eCbDnU8GpvmGbYuV65-PFrzjTKTEh= tk2ooJI7YemysqXdbLvCxzY$ for graphic product... ATTN...WFO...CTP...LWX...PBZ...RLX...RNK... ATTN...RFC...ALR...RHA...TIR...NWC... LAT...LON 41917883 41507851 40387890 39577797 39037791=20 38607814 37817889 37098013 37348123 38178071=20 39687991 40358027 41198027 41617949=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) .