Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 23 2024 05:14:04 AWUS01 KWNH 230513 FFGMPD VAZ000-NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-231000- Mesoscale Precipitation Discussion 0703 NWS Weather Prediction Center College Park MD 113 AM EDT Tue Jul 23 2024 Areas affected...Southern Appalachians Concerning...Heavy rainfall...Flash flooding possible Valid 230513Z - 231000Z Summary...Showers and thunderstorms will expand and train across the Southern Appalachians overnight. Rainfall rates of 1-2"/hr are likely, which could produce 1-3" of rain and instances of flash flooding. Discussion...The regional radar mosaic tonight shows reflectivity associated with strengthening convection expanding from northern AL into Upstate SC and western NC. This activity is forming within continued robust thermodynamics, and recent PWs as measured by GPS are 1.7-2.0 inches, overlapping a ribbon of MUCAPE of 1000-2000 J/kg. Forcing for ascent into this environment is being provided through the LFQ of a subtle jet streak arcing out of AR, PVA downstream of a weak mid-level perturbation noted in WV imagery lifting across TN, and low-level upslope/convergence on locally backed 850mb winds. Together, these features have resulted in a rapid expansion of the convective coverage, with radar-estimated rain rates rising to 1-1.5"/hr on KGSP and KHTX. The HRRR is slowly catching on to the expanded convective coverage, but the 00Z NAMNest seems to be initializing the best, with some support from the ARW2 as well. These models suggest that convection will continue to expand until the low-level flow veers again more to the WSW around 08Z-09Z. Before that time, the slightly backed flow will transport more substantial instability and PWs northward into the region, with more favorable upslope flow also occurring, to support additional convective development with rainfall rates reaching 1-2"/hr as progged by modest HREF probabilities. Additionally, mean 0-6km winds that are generally aligned to weak (5-10 kts) propagation vectors indicate the likelihood for training, and possibly some slower storm motions where terrain can influence updrafts. Where this occurs, total rainfall of 1-3" is likely, with locally higher amounts possible. This region has been wet recently as noted in AHPS 7-day rainfall that is 200-400% of normal. This has lowered FFG to 2-2.5"/3hrs across areas that are already generally more sensitive due to terrain. Although HREF FFG exceedance probabilities are minimal, likely due in part to a lack of model agreement and under-forecasting the current activity, anywhere the more intense rain rates train could result rapid runoff and flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5QNYTvS9bW_19LrTx5jviMScMe6CCZDq9t5uj27rPeVPhcfFLx_uYXI7ZoS3rixoikDm= n38HpZLEcOd5vcGtTUoFIcY$ for graphic product... ATTN...WFO...BMX...FFC...GSP...HUN...MRX...OHX...RNK... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 36838234 36768180 36568159 35868156 35078192=20 34648265 34468346 34398448 34358556 34428626=20 34658667 35058640 35668511 36198413 36708330=20 =20=20=20=20=20=20=20=20=20=20=20=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) .