AWUS01 KWNH 121858
FFGMPD
ALZ000-130055-

Mesoscale Precipitation Discussion 0998
NWS Weather Prediction Center College Park MD
258 PM EDT Thu Sep 12 2024

Areas affected...central to northern AL

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

Valid 121855Z - 130055Z

SUMMARY...A relatively focused/narrow axis or multiple axes of
heavy rain are expected to set up from central to northern AL
through 01Z. Rainfall rates of 1 to 2 in/hr are expected early on,
increasing potentially to about 3 in/hr on an isolated basis
toward 00Z. Flash flooding is considered likely with rainfall
totals potentially in the 3-5 inch range by 01Z.

DISCUSSION...18Z surface observations placed T.D. Francine around
20 miles east of GWO tracking toward the north near 10 kt.
Combining visible imagery with surface observations helped place a
warm front which extended from eastern AL into western AL,
southeastward into the FL Panhandle with mostly overcast skies to
its northeast along with one or two bands of moderate to heavy
rain. Broken cloud cover southwest of the warm front was allowing
sufficient solar insolation to support a nose of MLCAPE between
500 and 1000 J/kg over southwestern AL via the 18Z SPC
mesoanalysis. Low level convergence near the warm front in the 0
to 1 km AGL layer was fairly pronounced over west-central AL, with
ESE winds between 40-50 kt at 925 over central AL and
southwesterly winds of 20 kt in the warm sector at Mobile Bay (via
area VAD wind plots). Meanwhile, precipitable water values were
sampled across the region between 1.8 and 2.1 inches at 17Z via
GPS data.

The warm front is forecast to lift slowly northeastward through
00Z as continued daytime heating likely supports the advancement
of 1000+ J/kg MLCAPE northward into portions of central AL. While
some lowering magnitudes are expected as Francine continues to
track north, low level convergent flow will continue to support 1
or more axes of heavy rain into the late afternoon and early
evening over central to northern AL, oriented NNW to SSE, similar
to the mean steering flow which will allow for periods of
training. The environment supports rainfall rates of 1-2 in/hr,
but increasing instability through the afternoon and the approach
of left-exit region divergence within a 70-80 kt upper level jet
max forecast to strengthen and advance eastward from the lower
Sabine River Valley 00Z should help to increase rainfall
intensity. Increased forcing for ascent may allow training to
support rainfall rates near 3 in/hr by early evening. Localized
totals of 3 to 5 inches may occur through 01Z, potentially
overlapping with urban centers, including the Birmingham
metropolitan region. While not expected to be widespread across
central to northern AL, a couple areas of flash flooding will be
likely.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4fc5RrvpJY1Pj-Rsb_NL4RmSGIw4PkkDwSgE0L66pX5Gs9jJQF334tIOxJkoHpXQrp3s=
vHtuK6k9veqiFKy1HgX8Gis$  for graphic product...

ATTN...WFO...BMX...HUN...MOB...

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

LAT...LON   34858765 34358654 33558619 32458610 32048655=20
            32008735 32608779 34268797=20

=3D =3D =3D
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