Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 18 2024 03:28:53 AWUS01 KWNH 180328 FFGMPD VAZ000-NCZ000-180800- Mesoscale Precipitation Discussion 0646 NWS Weather Prediction Center College Park MD 1128 PM EDT Wed Jul 17 2024 Areas affected...far southern VA, northern NC Concerning...Heavy rainfall...Flash flooding possible Valid 180327Z - 180800Z Summary...Regenerating thunderstorms along an outflow boundary will persist for several more hours before waning overnight. Rainfall rates of 1-2"/hr are likely, which could produce 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this evening shows thunderstorms blossoming along an outflow boundary (OFB) aligned across parts of northeast NC into southeast VA. This outflow will continue to dive slowly southward, interacting with increasing 850mb inflow from the S/SW at 20-30 kts. This low-level inflow will resupply elevated PWs as high as 2.3 inches northward, and also draw some higher MUCAPE of 1000-2000 J/kg into the area. These thermodynamics will allow for a continuation of intense thunderstorms despite nocturnal overturning of the surface based instability, with ascent into this environment aided by a shortwave approaching from the west and isentropic ascent of the 850mb winds atop the OFB. Local radars across the area are estimating rainfall rates as much as 1.5"/hr, and a few flash flood warnings are already in effect. The high-res CAMs are struggling with the ongoing activity, and really do not reflect well the potential evolution through the next few hours. However, the presence of the multiple mechanisms for ascent within the persistently favorable thermodynamics, combined with evaluation of recent radar trends, suggests this setup will support continued heavy rainfall into the overnight. Mean 0-6km winds are generally aligned to the OFB, but Corfidi vectors are becoming increasingly aligned anti-parallel to the mean wind on the veering LLJ. This indicates a greater potential for backbuilding and regenerating storms, which is already present via the KRAX WSR-88D. With rain rates likely (50-70% from the HREF) reaching 1-2"/hr at times, the enhanced training that will result from backbuilding cells moving along the OFB could result in 2-3" of rain with locally higher amounts above 4" possible. 7-day rainfall in this area has been slightly above normal according to AHPS, but 0-10cm RSM from NASA SPoRT is still only 30-40% from recent dryness. This has allowed FFG to generally remain elevated at 2.5-3"/3hrs, which only has a 10-20% of exceedance according to the HREF. However, CAMs are struggling, and the environment supports training of intense rain rates which could overwhelm the soils, especially in urban areas. This could result in instances of flash flooding through the next several hours. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6jacF6JfgmdMKh9gxvhFPmAwnO0h42ehl7pgCVze_GjKAcVOJzFAn_QBtygXmuSDi3cM= GxpgFT46wOeiavJm4aXW4ZE$ for graphic product... ATTN...WFO...AKQ...GSP...MHX...RAH...RNK... ATTN...RFC...MARFC...SERFC...NWC... LAT...LON 37077844 36907695 36687620 36387575 36057559=20 35617557 35547603 35557671 35567824 35567918=20 35708000 36018058 36458059 36877993=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) .