Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 09 2025 00:33:32 AWUS01 KWNH 090032 FFGMPD DEZ000-MDZ000-VAZ000-WVZ000-090530- Mesoscale Precipitation Discussion 0625 NWS Weather Prediction Center College Park MD 831 PM EDT Tue Jul 08 2025 Areas affected...Much of Virginia into the DelMarVa Concerning...Heavy rainfall...Flash flooding possible Valid 090030Z - 090530Z Summary...Showers and thunderstorms will expand in coverage and gradually shift southeast through the evening. Rainfall rates of 1-2"/hr are expected, which through training could produce 2-3" of rainfall. Flash flooding is possible. Discussion...The regional radar mosaic early this evening shows an uptick in convective development from SW Virginia through the Tidewater Region. Above this developing convection, IR satellite imagery indicates an expansion of cloud tops falling below -50C, indicatative of the continued strengthening thunderstorms. This convection is blossoming in response to ascent driven by low-level convergence along a surface trough, weak isentropic lift as the modest 850mb LLJ surges northeast, and modest upper diffluence within the tail of jet streak centered over New England. This pronounced lift is acting upon rich thermodynamics created via PWs measured by the SPC RAP analysis of 1.9 to 2.1 inches, well above the 90th percentile for the date, collocated with a plume of MLCAPE exceeding 2500 J/kg. During the next few hours, this trough should pivot slowly southeast, continuing to provide the needed ascent for thunderstorm development despite the wane of daytime instability combined with convective overturning. The continued convection will be additionally supported by a subtle increase in the LLJ (reaching as high as 20 kts) to provide persistent isentropic ascent and thermodynamic resupply thanks to MUCAPE remaining above 1000 J/kg. This LLJ at 850mb is additionally progged to veer to be more aligned to the boundary, supporting enhanced training as storms develop in the next few hours. Although there continues to be some disagreement in the CAMs about the timing and spatial extent of convection through the evening, with rain rates forecast via HREF neighborhood probabilities to have a 60% (30%) chance of exceeding 1"/hr (2"/hr), any training could produce 2-3" of rain with locally higher amounts. Any location that receives training of these intense rain rates this evening could experience runoff capable of producing flash flooding. The greatest risk, however, appears to be generally from Richmond east to the coast where 0-10cm soil moisture from NASA SPoRT is above the 95th percentile and 1-hr FFG is locally as low as 1". Additionally the enhanced instability in the vicinity of the warm waters of the Chesapeake Bay could enhance any convection as well as the potential for regenerative and repeating cells. Although the risk should wane nocturnally, at least for the next few hours flash flooding will remain a threat across this area. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5ZK0Y3jwGBWWbPYaO-agBK4kMalvJRkWti0MSZCVtGZwXrzZd_pyr2yHX2D9j_sf59UP= rCzoT0UsYPC5mICba8pW2kU$ for graphic product... ATTN...WFO...AKQ...LWX...PHI...RNK... ATTN...RFC...ALR...RHA...TIR...NWC... LAT...LON 38627659 38507513 37937503 37267543 36787678=20 36577880 36588054 36918121 37478056 37977885=20 38427742=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) .