Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 26 2024 05:52:45 AWUS01 KWNH 260552 FFGMPD VAZ000-WVZ000-261030- Mesoscale Precipitation Discussion 1061 NWS Weather Prediction Center College Park MD 152 AM EDT Thu Sep 26 2024 Areas affected...eastern WV into central VA Concerning...Heavy rainfall...Flash flooding possible Valid 260548Z - 261030Z SUMMARY...A few areas of training will maintain a flash flood over the next 3-4 hours, but decreasing instability is expected to diminish the threat by 10Z. Peak rainfall rates of 1 to 1.5 in/hr are expected. DISCUSSION...Scattered showers and thunderstorms remained as of 0530Z across central/western VA into eastern WV. MRMS-derived rainfall rates over the past 2 hours have been peaking in the 1 to 1.5 in/hr range, mainly near areas of mesoscale rotation. Cells were being driven along the leading edge of moisture transport/warm air advection along an anomalous moisture plume extending well northward of Hurricane Helene located in the southern Gulf of Mexico. Low level upslope flow was also a factor with 20-30 kt of 925-850 mb oriented from the SSE, focused into the Blue Ridge and Appalachians Mountains, located beneath diffluent flow aloft to the east of an upper low positioned over the Lower OH Valley. A few factors are expected to influence flash flood potential over the next few hours. While a few pockets of south to north training and repeating are ongoing from eastern WV into western and central VA, instability has been...and will continue to fall...through the remainder of the night. A low level anticyclone off of the central Mid-Atlantic coast is forecast to shift eastward which should allow for veering of the low level flow in VA, with winds becoming oriented more parallel to the axis of terrain. While precipitable water values will remain high (1.5 to 2.5 standard deviations above the mean) and highly localized instances of higher rain rates may remain by 10Z, the overall threat is expected to diminish later this morning. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_2MzV1xwHkH74tyNhg-PRtf5AHCekb-1piLPcB9LunPN8SIIowq52t5W8RXcl3h8N5FG= AGIUlQs6EECw3Ti_eoZE5Zc$ for graphic product... ATTN...WFO...LWX...PBZ...RLX...RNK... ATTN...RFC...MARFC...OHRFC...SERFC...NWC... LAT...LON 39317873 38997788 38317828 37597878 37447924=20 37437971 37478029 37738058 38018053 38398036=20 38797995 39177930=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) .