AWUS01 KWNH 040937
FFGMPD
FLZ000-GAZ000-ALZ000-041535-

Mesoscale Precipitation Discussion 0856
NWS Weather Prediction Center College Park MD
536 AM EDT Fri Aug 04 2023

Areas affected...Eastern Alabama through Southwest Georgia into
North Florida

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

Valid 040935Z - 041535Z

SUMMARY...Repeating heavy thunderstorms expected to shift
southeast from northern Alabama through mid-morning. Reinforcement
of ample moisture and instability should lead to max hourly
rainfall of 2 to 3" over areas that have been fairly dry over the
past week. However, due to the extended duration of this heavy
rain, flash flooding is likely.

DISCUSSION...Mid-level impulses rounding a ridge axis extending up
the middle of the Great Plains has allowed organized thunderstorms
lines to develop in a rather narrow corridor over western TN and
northern AL with further upstream activity extending through
southeast MO. Hourly rainfall estimates from KHTX are up to 2.0 to
2.5" over portions of northern AL as of 0920Z.

Anti-cyclonically driven westerly low level flow of 15kt is
reinforcing a pool of high moisture (PWs of 2 to 2.2", 2 sigma
above normal) extending southeast from northern AL through
southern GA and upstream from a stationary front a little to the
southwest. An instability gradient is along the southern AL/GA
border with MUCAPE ranging from 500 to 2000 J/kg across southern
GA. The NW to SE orientation of the moisture axis, instability
gradient, and stationary front is parallel to the NWly 22kt deep
layer mean flow which means repeating activity can be expected to
continue as activity shifts southeast through mid-morning.

The 00Z ARW is performing admirably with this current and
generally features 1 to 2", with local maxima of several inches,
over the discussion area through 15Z. Given the heaviness already
seen and expected continued training, there is a likelihood for
max hourly rainfall of 2 to 3". Given FFG is generally 2.5 to 3"
in one hour over this relatively recently dry land, the risk of
exceeding FFG is considered likely and could reach scattered
coverage.

Jackson

ATTN...WFO...BMX...FFC...HUN...JAX...TAE...

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

LAT...LON 33898622 33878500 32918396 31638196 30948184
30298223 29918264 29928321 30178358 31128514
32898656 33888710

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