Flash Flood Guidance
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Issued by NWS
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895 AWUS01 KWNH 310055 FFGMPD MSZ000-LAZ000-ARZ000-310630- Mesoscale Precipitation Discussion 0352 NWS Weather Prediction Center College Park MD 854 PM EDT Thu May 30 2024 Areas affected...Central & Southern AR...Northern LA... Concerning...Heavy rainfall...Flash flooding possible Valid 310055Z - 310630Z SUMMARY...A narrow axis of unstable air downstream of decaying MCV in W AR, suggests slow moving efficient showers with potential for some stationary cells into overnight hours. Stronger thunderstorms capable of 2"/hr rates east and northeast of mature MCS entering N LA similarly pose potential for localized 2-3"+ totals and possible flash flooding incidents. DISCUSSION...A highly uncertain potential for highly focused/localized flash flooding may occur through the early overnight period across the discussion area. A rapidly decaying MCV, mid-scale shortwave from last night`s MCS continues to progress eastward into western AR at this time. Along/ahead of the wave through the southern and eastern quadrant, low to mid-level highly confluent and moisture rich air continues to wrap back toward the MCV with cells along the leading edge of the older outflow boundary continuing to slowly advance. Cells have modest but sufficient instability up to 1250 J/kg of MLCAPE and 20-25kt of moisture flux 1.5-1.75" TPW generally from central AR southward into west-central MS and northern LA. Cell motions will continue to be very slow as the dying MCV slides southeastward into the instability axis. This may allow for small pockets of enhanced deep layer convergence to support slow moving but deeper convection as suggested by a variety of Hi-Res CAMs including recent HRRR runs. This may support SHaRS-type flash flooding incident(s) with localized 2-3" totals resulting in possible flash flooding, which are difficult to pinpoint and highly dependent on some storm-scale interaction with the MCV downshear making confidence a bit lower. However, further south across northern LA and southern row of counties of central AR, flow intersects with the more mature MCS/MCV racing out of NE TX into NW LA; the effective warm front has slightly higher moisture and instability and with stronger convergence is supporting rates over 2"/hr. Cells have some meager training appearance through this axis in N LA to suggest a stripe of 2-3"+ totals are probably resulting in possible instances of flash flooding in the near term. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...JAN...LZK...SHV... ATTN...RFC...ABRFC...LMRFC...NWC... LAT...LON 35679303 35309220 33959128 32469112 31849171 32089342 33109342 33669301 34589324 35309347