Flash Flood Guidance
Issued by NWS
Issued by NWS
827 AWUS01 KWNH 250431 FFGMPD VAZ000-NCZ000-SCZ000-251029- Mesoscale Precipitation Discussion 1051 NWS Weather Prediction Center College Park MD 1230 AM EDT Wed Sep 25 2024 Areas affected...much of North Carolina, upstate South Carolina, and a small part of southern/southeastern Virginia Concerning...Heavy rainfall...Flash flooding possible Valid 250429Z - 251029Z Summary...Continued rounds of thunderstorms are expected to repeat/train across the discussion area through 08-09Z/4-5am Eastern. Rain rates exceeding 2 inches/hour at times are expected to result in at least localized flash flood concerns. Discussion...Over the last 2-3 hours, thunderstorms have focused along an axis extending from far northwestern South Carolina (near Spartanburg) east-northeastward through Raleigh/Durham and on to Roanoke Rapids. These storms were oriented parallel to west-southwesterly steering flow aloft, allowing for spots of localized training along the aforementioned axis. Additionally, enhanced low-level flow (around 25 knots across the Piedmont) were aiding in persistent low-level convergence along the axis while also maintaining 1000-1500 J/kg MLCAPE and 1.5-2 inch PW values within the pre-convective environment. These factors are continuing to support areas of 1-2 inch/hr rain rates at times that were threatening local FFG thresholds across the region (generally in the 1.5-2 inch/hr range - lowest in western and central North Carolina). This regime is expected to persist, with at least isolated flash flood potential materializing across the discussion area. A few spots of 4 inch rainfall totals are possible through 10Z. Some concern exists that the Raleigh/Durham area could experience heavier rain rates and urbanized flash flood potential overnight. Additional concerns exist across areas that have received 1-3 inch rainfall totals over the past 6 hours, where wet soils are likely to contribute to a greater risk for excessive runoff (especially in south-central/southeastern Virginia and central North Carolina). Moisture/instability profiles support redevelopment north of the primary convective axis (across northwestern North Carolina/southwestern Virginia) as well. Thunderstorms are expected to be a bit less focused in these areas (with lower potential for training/repeating). Isolated instances of flash flooding are still possible in this regime, however, especially where 1.5 inch/hr rain rates can materialize over sensitive/low spots. Cook ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...AKQ...CAE...GSP...MHX...RAH...RNK... ATTN...RFC...LMRFC...MARFC...SERFC...NWC... LAT...LON 37467723 36997655 36377659 35677725 35247924 34898198 35158287 35648240 36178142 36877979 37317834