AWUS01 KWNH 130049
FFGMPD
ALZ000-130645-

Mesoscale Precipitation Discussion 1000
NWS Weather Prediction Center College Park MD
848 PM EDT Thu Sep 12 2024

Areas affected...Northwest to Southeast Alabama...

Concerning...Heavy rainfall...Flash flooding possible

Valid 130050Z - 130645Z

SUMMARY...Regenerative thunderstorms along the front will continue
to repeat/train northward across central to northwest Alabama.=20
Focused banding to produce 2-4" streaks resulting in scattered
possible flash flooding through overnight period.

DISCUSSION...Post-tropical cyclone Francine continues a
north-northwest track and is nearing the Mississippi Delta
southwest of Memphis this hour.  Stronger theta-E gradient
analysis is helping to determine frontal structures to define a
narrow warm sector across southwest Alabama; however, higher Tds
are pooling along southeast AL/central FL panhandle, to slightly
enhance instability fields along the effective warm/stationary
front.  This boundary extends from a triple point near KTUP and
crosses through TCL to SEM and between GZH and K79J.  Stronger
return easterly component flow across the FL panhandle into SE AL
is also advecting the higher Tds in the low levels resulting in
the nose of deeper moisture across SE AL toward MGM.  The dry slot
through 700mb is out of the SSW and covers much of the warm sector
of SW AL but helps to steepen lapse rates across central AL
providing higher potential vigor.  Proximity to the eastern
gradient between the regimes along the front will likely continue
to be the area of greatest convergence and rainfall potential
given highest flux.=20


Instability is solid at about 1000+ J/kg but given the strength of
low level directional shear, some updrafts have been getting
sheared before greatest depth is achieved and 10.3um EIR loop
shows this with limited cold tops and orphaned cirrus canopies
racing northeast.   Still, the low level flux convergence given
0.9-1" in the Sfc-850mb layer through the length of the effective
warm front allows for efficient rainfall production with 1-1.5"/hr
short-term rates while allowing more of a south to north cell
motion given depth only is about to 850-750mb.

The potential for redevelopment along the strong but stationary
front will allow for repeating/training elements with streaks that
may align to support localized 2-4" totals.  As such, localized
flash flooding will continue to be possible, given likely limited
movement of the boundary and continued flux as the circulation
moves northwest directionally parallel to the frontal orientation.
 This may further pull the effective cold front back west or allow
for return wrap around moisture to over-top the convergence zone
across NW AL as well, expanding the potential for an incident or
two further up the effective warm frontal zone overnight.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!40hw24sZaVbexQr5LEp1y4Ae-rlWlvyWMZUT6nRKTkBeUBN4DveBR_UkotyvTvJQ2O8j=
TiA4cP9T3PjCMP80TEjd2KQ$  for graphic product...

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

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

LAT...LON   34938736 34548660 33698604 32968568 31548542=20
            31108614 31318684 31958737 32708775 33438796=20
            33908807 34418813 34838802=20

=3D =3D =3D
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