Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 08 2024 20:38:18 AWUS01 KWNH 082038 FFGMPD MDZ000-VAZ000-NCZ000-WVZ000-SCZ000-090230- Mesoscale Precipitation Discussion 0838 NWS Weather Prediction Center College Park MD 437 PM EDT Thu Aug 08 2024 Areas affected...Eastern Slopes & Foothills of Central and Southern Appalachians... Concerning...Heavy rainfall...Flash flooding possible Valid 082035Z - 090230Z SUMMARY...Strong moisture flux/upslope with broad areal average of ..5-1"/hr rates with occasional embedded 1.25-1.75"/hr particularly from NC north to E WV will induce rapid run off and potentially significant flash flooding conditions through the evening.=20 DISCUSSION...The center of T.S. Debby is close to crossing the SC state line into NC just east of Charlotte. Regional RADAR mosaic depicts a broadening downstream southeasterly onshore flow regime with numerous bands, increasing to as far north as the Chesapeake Bay area (a subsequent discussion will cover this area); while increasing deformation zone stratiform region continues to expand along and east of the spine of the Appalachians from Upstate SC to southwestern VA. Low level flow is starting to become more parallel to the terrain across the Carolinas given placement/orientation of the low to mid-level cyclone shifting north through central NC. The reduction of upslope component is starting to take effect as showers are reducing in intensity/coverage...though a few more hours (22-00z from south to north) of .5-1"/hr rates will continue to compound ongoing flooding conditions in the Carolinas before shifting northward. Across SW VA into central VA, the angle of sfc to 850mb flow is easterly with 30-35kts but is likely to veer slightly with time as the center of the low shears/shifts northward after 00z. Total Pwats through the layer are 2.25" are near 3.0 standard deviations from the mean and combined with strength of flux convergence with fairly good orthogonality to the ridge lines, should support enhanced rainfall rates of .75- 1.25"/hr. Broad totals of 2-3" in 3-6hrs are likely to induce flash flooding conditions is much of the slopes of the terrain given most areas are below 2"/3hr and 3"/6hr. Stronger banded convection across the Piedmont will have potential to lift into the terrain but will be highly localized but given weaker instability/vertical depth, short-term rates up to 2"/hr are possible and raise localized spots up to 4-5". This enhanced total in shorter duration will provide the greatest risk for considerable to significant flash flooding conditions, but will be more scattered in nature along though most probable in VA though 03z.=20=20=20=20=20=20 Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_ho6d29TDYmQlxJSMbBbVaLBYODg8izy1L9TIe4pUga8BHQ2g8tkOF1GFds2cFUPHnFJ= _TfSIjAs6kcpd3mPzAnmkjQ$ for graphic product... ATTN...WFO...GSP...LWX...RAH...RLX...RNK... ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC... LAT...LON 39617854 39517758 38537806 37967848 37087924=20 36247994 35678050 35158106 34788172 35028213=20 35998189 36678149 37578036 38607951=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) .