Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Sep 10 2023 15:20:04 AWUS01 KWNH 101519 FFGMPD MDZ000-VAZ000-NCZ000-WVZ000-TNZ000-KYZ000-102100- Mesoscale Precipitation Discussion 1051 NWS Weather Prediction Center College Park MD 1117 AM EDT Sun Sep 10 2023 Areas affected...Much of WV...W & SW VA...W MD...W NC...Far NE TN...Far E KY... Concerning...Heavy rainfall...Flash flooding possible Valid 101515Z - 102100Z SUMMARY...Short but intense downpours with sub-hourly totals of 1-1.5" and localized storm totals of 2"+ across saturated soils and steep grades suggest possible scattered incidents of flash flooding this afternoon. DISCUSSION...GOES-E WV suite depict the stagnant upper-level trof centered over the Appalachian Mountains continues to fill slowly but provide weak but sufficient corridor for enhanced lift and anomalous moisture again today. The most compact shortwave at least at 600-500mb is lifting across SW VA into S WV at this time, but SWIR/Visible imagery still denotes a mid-level wave (850-700mb) further south anchoring the base of the longer-wave deep layer trof across the central Smoky Mountains. This leaves an axis of deformation and confluence across central WV to W MD and W PA. Slow erosion of valley fog/stratus is burning away and temperatures are starting to respond rising into the 70s. Moist adiabatic profiles can quickly become unstable with SBCAPEs over 2000 J/kg even with small adjustments to the profile. Limited cap suggests 16-17z initiation along this confluence/convergence axis with best heating. Deep layer moisture is also remains pooled with values still AoA 1.5" through depth and with 11-13kFT of warm cloud layer, there should be solid warm cloud processes for quick rainfall efficiency to those updrafts. So the concern is even first cycle updrafts could produce a quick burst of 1-1.25" in 15 minutes. Given limited flow/shear, pulse style should dominate so totals up to 2" may 2.5" would be very localized but could easily overwhelm the saturated soils with very limited or no infiltration. Given naturally lower FFG in the sloped terrain enhanced by those saturated soils, scattered incidents of flash flooding are possible.=20=20 Cold pools should support favored eastward outflow propagation into better unstable air, likely kicking off additional updrafts, though deeper steering may limit eastward extent, relative to further south of the shortwave where 700-400mb steering veers back to westerly. Still, places in closest proximity between the low to mid-level vorticity center in NW NC and the exiting 500mb wave into WV have increased potential of some stationary cell motions for highest overall totals, but this is too difficult to nail down precise locations given storm scale interactions that will unfold into the afternoon hours... so spots across the eastern slopes of the Smokies into NW NC/SW VA remain under similar flash flooding risk and are incorporated into this MPD. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!669jkooSvCHK0Gdz2Yuyjeu5Jqm7SdubAvsBJR1BT1B2EdcY3K-eln2Tj3xIDLHKvXop= oG3bi1hlOJXGJEu-sgDZ3PE$ for graphic product... ATTN...WFO...GSP...JKL...LWX...MRX...PBZ...RLX...RNK... ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC... LAT...LON 39677924 39667857 39397824 38797833 38297905=20 37638000 36838038 36178070 35338229 35138284=20 35158332 35318353 35688336 35968295 36378268=20 37188262 37758227 38218183 38648129 39208055=20 39577987=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .