Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Sep 16 2025 08:33:16 AWUS01 KWNH 160833 FFGMPD VAZ000-NCZ000-161400- Mesoscale Precipitation Discussion 1090 NWS Weather Prediction Center College Park MD 432 AM EDT Tue Sep 16 2025 Areas affected...coastal southeastern VA and northeastern NC Concerning...Heavy rainfall...Flash flooding possible Valid 160831Z - 161400Z Summary...At least a localized flash flood threat looks to be increasing across coastal sections of southeastern VA and northeastern NC this morning. Increasing rainfall rates with hourly totals potentially reaching 3 inches are expected to impact a few coastal locations through 14Z. Discussion...08Z surface observations and shortwave IR imagery from GOES East showed a surface low centered about 65 miles east of Cape Hatteras. Over the past 6 hours, the surface low has been gradually lifting north to northwest while occasional mesoscale lows have appeared in the broader low level cloud swirl in satellite imagery. It appears the main surface low has been associated with the most recent burst of convection to its northwest, with area radar imagery showing reflectivity echoes crossing over Hatteras Island. SPC mesoanalysis data from 08Z showed the convective burst along the western edge of a MLCAPE bubble offshore within 1000-2000 J/kg, just east of the northern Outer Banks. Meanwhile, moderate to occasionally heavy rain has been observed over VA, to the southwest of Norfolk, with 1-2 inches reported since midnight. However, a lack of better instability has limited rainfall intensity for inland locations. Short term RAP guidance over the past 6-10 cycles has been in relatively good agreement with the current surface low position and supports the low tracking toward the northwest, closer to the Outer Banks, through 14Z. This movement makes sense given the low's placement relative to a closed mid-level low centered over the central NC/SC border. Even if the RAP is wrong, there is the potential for convectively induced mesovortices within convection that may reach the coast before dissipating. An expected northwestward movement of the surface low should support increasing MLCAPE from roughly Cape Hatteras to Virginia Beach with values of 500 J/kg to the north and up to ~1500 J/kg over Hatteras Island by 12-14Z. In addition, a primary axis of low level convergence to the northwest of the low center is expected to make it to the northeastern NC and southeastern VA coast with increasing rainfall intensities beneath favorably diffluent flow in the upper levels. Additional, weaker and more transient axes of low level convergence will be possible farther inland from the coast which could support increased rainfall intensities as instability increases later this morning. Earlier gauge observations had shown ~0.75 inches of rain in 15 minutes which would support hourly rainfall up to 3 inches. Expected hourly rainfall of 1 to 3 inches will be possible from portions of northeastern NC into southeastern VA which may result in localized flash flooding, especially over any urban locations. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_qFJKYsDtL4cZcV9URN8n6DzfJPHVrjrdZ4SrWpKuYZJT3MpZOotEOBGA3Yh_Nh-nYXj= iy_iNscaFNoTEa2lzNuZGzE$ for graphic product... ATTN...WFO...AKQ...MHX...RAH... ATTN...RFC...ALR...RHA...NWC... LAT...LON 37197676 37137627 36787569 35957506 35177532=20 35167600 35567677 36077735 36497755 37067729=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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .