Summary...Another round of life-threatening and locally
catastrophic flash flooding continues just inland from the central
Gulf Coast over southern Mississippi, Alabama and the Florida
Panhandle through midnight. Convergent rain bands with 2 to 4"/hr
rainfall rates are likely to persist with additional 4 to 8"+
forecast through midnight. Widespread flash flooding resumes, with
locally catastrophic impacts likely where these heavy rates
persist and overlap heavy rainfall from the past 12hrs. extreme
band persists occurs.
Discussion...As of 2330Z, two particularly heavy clusters of
thunderstorms are over southern MS and southern AL with hourly
rainfall of 2 to 3" estimated from KMOB with an eastward motion.
These developed in the lee of the previous slow moving line that
worked east over southern AL/FL Panhandle this afternoon. Rain
rates around 1.5"/hr are see on the eastern AL/FL border from the
last part of the original band. This activity is falling over
areas that already received 4 to 14" in the past 12hrs,
particularly over southern MS.
The remnant low from Arthur is over central AL with a trough and
focus for development extending southwest where this new
development is. Convergence along this boundary is occurring from
35kt SWly flow from the Gulf. PW of 2.4" is pooling along this
trough and will continue to feed very heavy rainfall.
Recent HRRR and RRFS runs indicate several more inches of rainfall
along this corridor through 04Z with estimates in the 4-8" range.
This will cause widespread considerable flash flooding with
locally catastrophic impacts, particularly where the highest
amounts fall and where any elevated amounts fall over areas that
already received multiple inches. CAMs indicate activity waning
after midnight, though that will need to be monitored as the
evening progresses given the slow motion of the Arthur remnants.
