Flash Flood Guidance
Issued by NWS
Issued by NWS
850 AWUS01 KWNH 151604 FFGMPD FLZ000-ALZ000-MSZ000-LAZ000-152200- Mesoscale Precipitation Discussion 1014 NWS Weather Prediction Center College Park MD 1203 PM EDT Sun Sep 15 2024 Areas affected...north-central MS to southern MS/AL and western FL Panhandle Concerning...Heavy rainfall...Flash flooding possible Valid 151602Z - 152200Z SUMMARY...Areas of training are expected to develop from the central Gulf Coast into southwestern AL and central/eastern MS through 22Z. Rainfall rates of 1 to 3 in/hr are likely, which may result in localized areas of flash flooding. DISCUSSION...At 1530Z, visible satellite imagery showed thick cloud cover over much of central to northern MS while skies over southern MS into the Mobile Bay region had only scattered clouds. A low located in the 925-850 mb layer was identified over south-central MS via area VAD wind plots with very slow movement over the past few hours. Low level ESE winds of 20-30 kt were present to the east of the low over eastern portions of MS into AL while wind speeds dropped off to the west along the AR/MS border down to Mobile Bay. A combination of speed and directional low level convergence was supporting a broken axis of mostly warm topped showers from northeastern MS down to the offshore waters of MS/AL with increasing development noted across the southern/clearer-sky regions. The environment was very moist with area 12Z soundings indicating precipitable water values of 1.6 to 2.0 inches and wet bulb zero heights between 13-14 kft. SPC mesoanalysis data from 15Z showed that MLCAPE of 500 to 1500 J/kg was focused from the central MS/AL border, southward to the Gulf Coast from central LA to the FL Panhandle, with higher values toward the south. Daytime heating is expected to expand the coverage of 500 to 1500 J/kg MLCAPE across the region but likely keeping the better instability focused over southern areas where greater solar insolation is expected. Scattered showers and thunderstorms will likely increase through the afternoon with cell movement following the general flow around the MS low. However, slow movement and training will be possible with cells that form along the low level convergence axis from north-central MS to the southern MS/AL border, where lower topped cells will have a motion roughly parallel to the axis of convergence. Stronger low level convergence is expected from central to northern MS where greater coverage of rain is expected but lower instability may cap rain rates below 2 in/hr. Farther south, rainfall rates may get as high as 3 in/hr due to the greater instability combined with potential for slow movement but coverage will likely be more isolated compared to up north. Portions of this region have been anomalously wet over the past several days, but other portions have missed out on the bulk of rainfall and are nearer to average. At least localized flash flooding will be possible through the afternoon. Otto ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...BMX...JAN...LIX...MEG...MOB... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 34089005 34078912 33328834 31958748 30698644 30098675 29918785 29998896 30388928 31508959 33139025