Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 29 2024 17:52:32 AWUS01 KWNH 291752 FFGMPD PAZ000-MDZ000-VAZ000-DCZ000-WVZ000-292350- Mesoscale Precipitation Discussion 0944 NWS Weather Prediction Center College Park MD 151 PM EDT Thu Aug 29 2024 Areas affected...Central Appalachians into the Piedmont of the Mid-Atlantic Concerning...Heavy rainfall...Flash flooding likely Valid 291750Z - 292350Z SUMMARY...Developing and expanding areas of slow-moving showers and thunderstorms are expected going through the afternoon and early evening hours. Given slow cell-motions and heavy rainfall rates up to 2 inches/hour, scattered instances of flash flooding will be likely. DISCUSSION...The midday GOES-E GeoColor satellite imagery along with LightningCast data shows convective initiation taking place across the higher terrain of the central Appalachians as strong diurnal heating promotes increasing surface-based instability along with corresponding terrain-induced circulations for convective development. Away from the terrain across the Piedmont of the Mid-Atlantic, there is still some low-level CINH in place, but MLCAPE values here have risen to as high as 1500 J/kg, with satellite imagery showing plenty of strong solar insolation that will drive increasing instability over the next several hours. Scattered to broken areas of showers and thunderstorms will initially be focused over the higher terrain of the central Appalachians including the Blue Ridge from central PA down through western MD and into much of eastern WV and western VA. However, there will gradually be the development of convection farther east into portions of the Piedmont from south-central PA down through central VA by later this afternoon. This will be aided by proximity of a backdoor cold front that has been gradually settling south across the coastal plain but is becoming quasi-stationary near the eastern slopes of the Blue Ridge. The airmass especially in the boundary layer is quite moist with the latest surface observations showing dewpoints in the low to mid-70s. However, the CIRA-ALPW data shows this moisture concentration extending well up into the 700/500 mb layer as well. Additionally, the CIRA-ALPW is showing evidence of some weak shortwave energy/MCV activity advancing east-southeast across southeast OH and heading for the central Appalachians. Between the improving thermodynamic environment, localized frontal convergence, upslope flow into at least the eastern slopes of the higher terrain including the Blue Ridge, and approaching upstream vort energy, convection will be on the increase in terms of coverage and intensity over the next several hours. Rainfall rates will be capable of reaching 2 inches/hour rather easily with the stronger storms, and with expectations of slow-moving cells and locally terrain-focused convection, some rainfall totals by early this evening may reach 2 to 4 inches with isolated heavier amounts. These rains will likely result in scattered instances of flash flooding which may eventually including impacts east of the Blue Ridge but along and west of the urbanized I-95 corridor from Baltimore, MD down through Washington D.C. on down to Richmond, VA. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9f145iJ-ktb_ZP99gLGOZ1opAJQErWXmkRmEWVjndPJaT27Z1-897buX1ApigoGzFjjs= aLdmdtTnM4EVOtBCNXtuXX4$ for graphic product... ATTN...WFO...AKQ...CTP...LWX...PBZ...RLX...RNK... ATTN...RFC...MARFC...NERFC...OHRFC...SERFC...NWC... LAT...LON 41897810 41757712 40677679 39277680 37937723=20 37197804 36917872 36797991 37268079 37928082=20 38778002 39727942 41197886=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) .