Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 13 2025 14:27:21 AWUS01 KWNH 131426 FFGMPD NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-132025- Mesoscale Precipitation Discussion 0925 NWS Weather Prediction Center College Park MD 1025 AM EDT Wed Aug 13 2025 Areas affected...Portions of the Central Appalachians and Mid-Atlantic Concerning...Heavy rainfall...Flash flooding likely Valid 131425Z - 132025Z SUMMARY...Clusters of heavy showers and thunderstorms with locally extreme rainfall rates will tend to expand in coverage over the next several hours. Scattered areas of flash flooding will gradually become likely, and especially later this afternoon closer to the I-95 corridor of the Mid-Atlantic where an urban flash flood threat is expected to evolve. DISCUSSION...The latest satellite and radar imagery shows a band of heavy showers and thunderstorms moving into northern WV, and the latest trends show cooling cloud tops associated with this activity. This convection is associated with the southwest flank of mid-level vort energy going into the central Appalachians which is embedded within a very moist and moderately unstable environment. MLCAPE values across northern WV and western MD, and areas east of the Blue Ridge over the Mid-Atlantic, are locally on the order of 1000+ J/kg. However, the PWs are quite high and locally over 2 standard deviations above normal. In fact, the 12Z RAOB soundings from KPIT and KIAD showed PWs of 1.86 and 2.22 inches respectively with tall skinny CAPE profiles and elevated WBZ/freezing levels. This is strongly suggestive of a very efficient and tropical environment that will promote highly efficient processes for locally extreme rainfall rates that may reach well into the 2 to 3+ inch/hour range. Convection should tend to generally build in coverage over the next several hours as this vort energy advances off to the east across the central Appalachians and northern Mid-Atlantic region. This will support heavy showers and thunderstorms advancing east through central and northern WV, western MD and southwest PA in the near-term. However, as instability and convergent low-level flow becomes better established this afternoon east of the Blue Ridge and into the Chesapeake Bay region, there will likely be the development and expansion of very heavy showers and thunderstorms across much of northern VA, central to northeast MD and southern PA, including areas along the I-95 corridor from Washington D.C. to Philadelphia. The latest hires model guidance may be underplaying the rainfall potential given the level of moisture that is in place, and there will the influence of diurnal heating and orographics that will also support an uptick in coverage of showers and thunderstorms. Slow cell-motions and localized cell-training concerns coupled with locally extreme rainfall rates may support some localized rainfall totals of 3 to 5 inches. Areas of scattered flash flooding will become likely in time, and this will include an increasing urban flash flood threat near the I-95 corridor by later this afternoon. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_BDgP8HIv5WDq8BcVl3dNGRRle70i2vNKdHEmFfl2ZsQtkVHeh08Ox-BZ5pMJwmlNwHH= O9WllFgWJyH_VkEemcudl3o$ for graphic product... ATTN...WFO...AKQ...BGM...CTP...LWX...PBZ...PHI...RLX...RNK... ATTN...RFC...RHA...TIR...NWC... LAT...LON 41027601 40757482 39907456 39127511 38337647=20 37887805 37677977 37758073 38308145 39238129=20 39828054 40087923 40477767=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .