Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat May 27 2023 17:06:59 AWUS01 KWNH 271706 FFGMPD NCZ000-SCZ000-272300- Mesoscale Precipitation Discussion 0355 NWS Weather Prediction Center College Park MD 106 PM EDT Sat May 27 2023 Areas affected...Southern NC...Coastal Northern SC Concerning...Heavy rainfall...Flash flooding possible Valid 271705Z - 272300Z SUMMARY...A developing conveyor belt of strong thunderstorms containing excessive rainfall rates >2"/hr may lead to areas of flash flooding this afternoon. DISCUSSION...GOES-16 is depicting thunderstorms off the southern NC and SC coasts have grown increasingly more intense over the past hour as the warm front lifts north. At 925mb, south to southeasterly winds on the east side of the storm off the GA coast are streaming north while northeasterly winds over southern NC converge with the aforementioned southerly component. This will act as an ideal convergence zone to allow more rounds of storms to develop. SPC RAP mesoanalysis shows and increase of 200-400 J/kg of MLCAPE just offshore over the past 3-hours. PWs from Myrtle Beach on north and east to Cape Lookout will range between 1.6-1.8" this afternoon, which combined with the steadily rising MLCAPE along the coast will be sufficient for hourly rainfall rates ranging between 2-3"/hr this afternoon. The instability and available moisture are not the only favorable factors for Excessive Rainfall this afternoon. RAP soundings for this afternoon show warm cloud layers as deep as 12,000ft in some cases and LCL-EL mean RH values >90%. These variables support approaching storms as being efficient rainfall producers. In addition, there will be as much as 30-40 knots of 0-6km bulk shear and 0-3km SRH values >300 m2/s2. Not only will these cells reside in a thermodynamically favored environment, but these cells may contain mesocyclones that are also more efficient rainfall producers. Lastly, the slow progression of the storm system and the large dome of high pressure to the north are likely to maintain this strong low-level convergence zone into the afternoon and evening hours, making it possible for segments of thunderstorms to potentially train over parts of the at-risk area. The 12Z HREF shows the best probabilities (20-30%) for >2"/hr rainfall rates will reside along the coastline from Bald Head Island to Cape Lookout. Similar rainfall rates are possible as far south as Oak Island and Myrtle Beach, especially if the barrage of strengthening cells to the south trains over these areas. The more heavily urbanized communities and poor drainage spots are most susceptible to flash flooding this afternoon. The flash flood threat may linger deeper into the evening over southeast NC where the steady diet of Atlantic moisture and lingering instability keeps the excessive rainfall threat around into tonight. Mullinax ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4YJirIt05eRqlIHxD-sI3dQz_fTeDqS3zxRve524aaDifOVy3JpN7gpeaoZf9m08viWd= 3esmMJ7alhsvCEz4SvUmBQg$ for graphic product... ATTN...WFO...ILM...MHX... ATTN...RFC...SERFC...NWC... LAT...LON 34867685 34637644 34277730 33797792 33567863=20 33227900 33227922 33387930 33667917 33977887=20 34207826 34647762=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) .