Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Aug 07 2024 16:00:23 AWUS01 KWNH 071600 FFGMPD NCZ000-SCZ000-072100- Mesoscale Precipitation Discussion 0826 NWS Weather Prediction Center College Park MD 1159 AM EDT Wed Aug 07 2024 Areas affected...Coastal Plains of North Carolina and northern South Carolina Concerning...Heavy rainfall...Flash flooding possible Valid 071558Z - 072100Z Summary...Spiral rain bands around Tropical Storm Debby will periodically pivot onshore through the evening. Rainfall rates within these bands will likely reach 2-3"/hr at times, resulting in corridors of 2-4" of rain through training. Flash flooding is possible. Discussion...Tropical Storm Debby is clearly evident on GOES-E visible imagery this morning drifting slowly off of the South Carolina coast. Although significant dry air has worked in towards the center of Debby, GOES-E WV imagery shows a channel of extremely moist air noted as well by CIRA experimental sfc-850mb PW above the 99th percentile. Within this plume of higher moisture, which has PWs measured by recent NUCAPS satellite soundings of around 2.5 inches, bands of rainfall have intensified and are streaming N/NW around Debby. Although they have generally struggled to advect onshore due to modest instability noted via the SPC RAP analysis of 500-1000 J/kg, a steady increase in the last 3 hours of this MLCAPE is allowing for more widespread coverage of stronger reflectivity to spread onshore. Recent radar-estimated rain rates from KMHX WSR-88D have reached as high as 1.5"/hr, leading to a few pockets of 1-2" of rain in the last 3 hours according to MRMS. Confidence in the evolution the next several hours is somewhat uncertain due to how poorly organized Debby looks right now, but the CAMs do indicate that convection should continue to stream onshore within the pivoting bands, and eventually expand onshore. This is supported not only by the CAMs simulated reflectivity, but also by the ingredients as PWs rise to nearly 2.75" this aftn in conjunction with increasing destabilization. The placement of any given band is challenging to identify even at short time scales, but intense rain rates of 2"/hr (HREF neighborhood probabilities 30-40%) or more (HRRR 15-min accumulations as much as 0.75") within any of these bands could cause flash flood instances, especially within any more pronounced training where 2-4" of rain is likely. The potential for flash flooding will be most likely across urban areas or where soils are fully saturated (NASA SPoRT 0-10cm RSM above 98%) from recent heavy rains associated with Debby. Additionally, although confidence is a bit lower, a more consolidated region of heavy rainfall may develop just west of the broad center of Debby along a surface trough and where an instability gradient is progged to sharpen. If this occurs, more continuous moderate to heavy rain rates could train N to S, potentially across the Pee Dee or Lowcounty where rainfall has already been significant. If this occurs, it could enhance the flash flood threat across this area as well, separate from the spiral bands pivoting onshore to the north. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7xeeE6HMIrK7BX5NUOs-TbjRIZXXiZhEveQPf29CRUBbtQ01CtgbyVtSXBMYSWn2ZBIl= 5fTpHGA90MJQyWKXJOuoT74$ for graphic product... ATTN...WFO...AKQ...CAE...CHS...ILM...MHX...RAH... ATTN...RFC...SERFC...NWC... LAT...LON 36177600 36007558 35577537 35127557 34447677=20 33857795 33687866 33417905 33237933 32917982=20 32958011 33298031 33708034 34088011 34377969=20 34687914 35237840 35637753 36027673=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) .