370
AWUS01 KWNH 150732
FFGMPD
FLZ000-GAZ000-ALZ000-151230-

Mesoscale Precipitation Discussion 1013
NWS Weather Prediction Center College Park MD
330 AM EDT Sun Sep 15 2024

Areas affected...Far Southeast AL...Portions of the FL Panhandle

Concerning...Heavy rainfall...Flash flooding likely

Valid 150730Z - 151230Z

SUMMARY...Locally very slow-moving to occasionally stationary
thunderstorms with extreme rainfall rates continue to impact
portions of far southeast AL and the FL Panhandle. Additional
flash flooding is expected going through dawn, with locally severe
flash flooding impacts likely to continue in the near-term.

DISCUSSION...The latest radar imagery shows areas of very
slow-moving to occasionally stationary thunderstorms over far
southeast AL and portions of the FL Panhandle. The convection
continues to be focused along a low-level and nearly stationary
axis of focused moisture convergence within a relatively unstable
environment characterized by MUCAPE values of 500 to 1000 J/kg.
Somewhat high instability parameters are noted closer to the
Apalachicola area and the Gulf Coast where there is evidence of a
weak wave of low pressure focused along a quasi-stationary front.
Coinciding with this axis of instability is also still the
proximity of stronger kinematics as strong mid to upper-level flow
continues to overrun the region which is favoring some relatively
elevated effective bulk shear parameters, and especially over the
FL Panhandle.

PWs are on the order of 1.8 to 2.0 inches and this coupled with
the instability and shear magnitudes continues to favor an
environment conducive for very slow-moving thunderstorms with
extreme rainfall rates of 2 to 4 inches/hour. Marianna, FL (KMAI)
has picked up 5.90 inches of rain in just the last two hours from
05Z to 07Z from the cells moving very slowly westward across
Jackson County.

While the overall coverage of convection is limited, the cells
that are developing in this regime are very slow-moving and
occasionally stationary which is fostering extremely heavy
rainfall totals. The latest HRRR guidance, the 00Z NAM-Conest/FV3
LAM solutions from the HREF, and the 00Z NSSL MPAS solutions
continue to support small-scale areas of strong thunderstorms that
may yield an additional 3 to 6+ inches of rain going through dawn
across parts of far southeast AL and the FL Panhandle.

Areas of flash flooding are ongoing and additional small-scale
areas of flash flooding are likely to develop which will include
locally severe and life-threatening impacts where these heavier
rainfall rates and totals materialize going through dawn.

Orrison

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...BMX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON   31828565 31738517 31378497 30918488 30278463
            29958456 29678464 29628515 30018568 30838617
            31348625 31698603