Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jun 28 2025 18:22:28 AWUS01 KWNH 281821 FFGMPD VAZ000-NCZ000-WVZ000-SCZ000-GAZ000-TNZ000-KYZ000-290030- Mesoscale Precipitation Discussion 0541 NWS Weather Prediction Center College Park MD 220 PM EDT Sat Jun 28 2025 Areas affected...Central Appalachians Concerning...Heavy rainfall...Flash flooding possible Valid 281830Z - 290030Z Summary...Slow moving showers and thunderstorms will rapidly increase in coverage across the Central Appalachians this afternoon. Rainfall rates of 1-3"/hr are likely within this convection, leading to pockets of 2-3" of rain with isolated higher amounts. Flash flooding is possible. Discussion...The GOES-E visible imagery this afternoon shows rapid growth of TCu from northern GA through central VA, primarily along the higher terrain of the Appalachians. These storms are pulsing up in an extremely favorable thermodynamic environment reflected by SPC RAP analyzed SBCAPE of 2500-3500 J/kg overlapping PWs above 1.7 inches. Morning forecast soundings across the area indicate long-skinny CAPE profiles and generally moist-adiabatic lapse rates through much of the column, which when combined with warm cloud depths approaching 13,000 feet suggests the environment will support efficient warm-rain processes. Although synoptic ascent is weak outside of modest upslope flow, which is reflected by weak winds from the sfc through 300mb, there will likely be scattered to numerous thunderstorms which form across the area through this evening. Convection will generally form along terrain features today. As these storms pulse and decay, remnant outflow boundaries will serve as additional foci for updrafts, leading to more numerous cells later this aftn/eve. Storm motions will be quite weak and chaotic as reflected by 0-6km mean winds of just 5 kts and variable but weak Corfidi vectors, suggesting cells will move little during their lifespan, and may at time stall when they become terrain-tied. With rain rates progged by the HREF to have a 20-25% chance of exceeding 2"/hr, and HRRR 15-min rainfall forecast to be as much as 1" (brief 4"/hr rates - supported by the efficient warm rain processes), these slow storms, especially during collisions/mergers or when storms become terrain tied, could lead to pockets of 2-3" of rain with locally higher amounts. The Central Appalachians have generally been dry the past 7-10 days as noted in the AHPS rainfall departures, but scattered storms in the past week have created some pockets of more than 200% of normal rainfall. This has led to areas of 3-hr FFG that is as low as 1-1.5"/3hrs, although FFG across much of the region is modest due to the general vulnerability of this terrain. The HREF 3-hr exceedance probabilities are very scattered and peak at just 10-20%, but the slow movement of these efficient rain rates atop generally sensitive terrain could result in at least isolated instances of flash flooding today. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_5I1_Zdh-v0uJ9uoyAiR1D_tmHe7sg0TUtvuLAMqBBnuTixMBo9ppn3IBlX0VD9trs3g= sRA8u4fsye79COmzrpKLfIM$ for graphic product... ATTN...WFO...AKQ...FFC...GSP...JKL...LWX...MRX...RAH...RLX... RNK... ATTN...RFC...ALR...ORN...RHA...TIR...NWC... LAT...LON 38707847 38457811 37717845 36927961 36168046=20 36138055 35468118 35028165 34608230 34558401=20 35018444 35808384 36858294 37748159 38368034=20 38677927=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) .