Severe Thunderstorm Warning 47, NWS Tallahassee, FL

Area Forecast Discussion
National Weather Service Tallahassee FL
429 PM EDT Thu Mar 13 2025

...New NEAR TERM, SHORT TERM, LONG TERM, MARINE, FIRE WEATHER,
HYDROLOGY...

.NEAR TERM...
(Through Friday)
Issued at 332 PM EDT Thu Mar 13 2025

Showers with embedded thunderstorms are ongoing northwest of the
FL Big Bend as of around 4 PM ET, but will eventually make their
way into the FL Big Bend. The main threats are large hail and
isolated damaging wind gusts until activity dissipates between
8 PM and 10 PM ET. This is supported by lift provided by a stout
shortwave moving through aloft in conjunction with favorable
jet dynamics. Steep mid-level lapse rates and 500 hPa temps near
-20C are supporting the hail threat. Despite modest low to mid-
level lapse rates, the wind field aloft is increasing through
this evening, so we may begin to see more storms with isolated
damaging wind potential, as opposed to mostly hail producers
as of around 4 PM ET. Once this activity moves east into early
tonight, expect a drying trend, with fog taking center stage.

Much of the guidance supports fog development after midnight
across the region. The setup is favorable for areas of fog to
become dense between roughly 5 AM ET/4AM CT and 10 AM ET/9 AM
CT. If confidence increases, a Dense Fog Advisory would be
needed eventually due to impacts to Friday morning commute.

On Friday, dry weather is expected with Southerly winds increasing
by late morning, with gusts around 15 to 20 mph through the
afternoon. While the air mass remains modestly moist, expect lower
dewpoints during the aftn and evening closer to the I-75 corridor of
GA due to turbulent mixing. Lows tonight in the 50s and highs on
Friday around 80 degrees.

&&

.SHORT TERM...
(Friday night through Sunday)
Issued at 332 PM EDT Thu Mar 13 2025

A high-end severe weather outbreak is on the way for Saturday
night through about midday Sunday.

A strong upper level southern stream trough will be moving across
Texas on Saturday, with a strong and cyclonically curved speed max
working through the base of the trough. A surface cold front will
move from west to east across the region on Sunday, trailing from
a deep surface low passing well to the north. As the jet stream
crosses over the front and across a moderately unstable pre-
frontal air mass, there will be a prime setup for a QLCS
thunderstorm squall line to develop over the Lower Mississippi
Valley and make eastward progress. In advance of the line, a very
strong S-SW low-level jet of 50-60 knots will develop after
sunset on Saturday evening. Deep-layer bulk shear values around
55-70 knots will characterize the convective environment, and
low-level hodographs will be curved and long. With a squall line
such as this, damaging or destructive wind gusts will be the
result, with embedded tornadoes. If any discrete supercells kick
off in advance of the line, these would be concerning and have
potential for strong tornadoes.

This far in advance, timing should be treated with broad strokes.
Generally speaking, areas west of the Apalachicola and Flint
Rivers will be their main threat from about 8 pm to 3 am CT. East
of there to the U.S. 319 corridor, the pre-dawn hours on Sunday
are the concern. East of US Hwy 319, the main threat will come
from the near-sunrise hours through Sunday morning.

As storms move east across the 319 corridor, instability will
become weaker. This will hopefully take the worst punch out of the
severe event, but strong to severe storms will continue all the
way east through out service area on Sunday morning.

Otherwise, southerly gradient winds in advance of the squall line
will become strong. Non-thunderstorm wind gusts near 40 mph are
possible across most any county on Saturday afternoon and evening,
which is enough to cause light tree damage and spotty power
outages. Again, this is before the squall line arrives.

&&

.LONG TERM...
(Sunday night through Thursday)
Issued at 332 PM EDT Thu Mar 13 2025

Behind the cold front, high pressure at the surface and aloft will
fill in starting Sunday night. A drier air mass will arrive from
the west, and surface high pressure will pass directly overhead on
Monday night. With the air mass arriving more from the west than
the north, afternoon temperatures on Monday will merely cool off
to near normal. Great radiational cooling on Monday night will
bring most inland locations to see lows in the lower 40s, perhaps
even pockets of upper 30s.

Another broad and energetic upper trough will move across the
Southeast States next Wednesday and Thursday. This will bring the
next cold front, with potential for pre-frontal strong or severe
thunderstorms centered timewise around Wednesday night.

&&

.AVIATION...
(18Z TAFS)
Issued at 131 PM EDT Thu Mar 13 2025

Brief MVFR restrictions possible in TSRA this aftn and evening
at most terminals, with the exception of a PROB30 at VLD. TSRA
should end around 00Z, followed by IFR/LIFR at all terminals,
commencing between 06Z-10Z generally west to east and lifting
by 14Z. Expect most terminals should return to VFR by Noontime.

&&

.MARINE...
Issued at 332 PM EDT Thu Mar 13 2025

Southerly flow will freshen over the course of Friday and
Saturday, in advance of a severe thunderstorm squall line and cold
front late Saturday night and Sunday morning. In the pre-frontal
southerlies Saturday afternoon and evening, strong breezes with
near-gale gusts are expected. Behind the front late Sunday and
Sunday night, fresh to possibly strong northwesterlies and
northerlies will fill in. Winds will decrease on Monday, and
surface high pressure will move directly across the waters on
Monday night.

&&

.FIRE WEATHER...
Issued at 332 PM EDT Thu Mar 13 2025

Showers and thunderstorms are expected Thursday afternoon and
evening across much of the region. Hail, along with gusty and
erratic winds, can be expected with the stronger storms.

Dry weather returns for Friday, when high mixing heights and
brisk southerly transport winds, will lead to the potential for
pockets of high dispersion mainly north of I-10.

Strong southerly 20ft and transport winds will lead to high
dispersions on Saturday, with dry weather continuing.

&&

.HYDROLOGY...
Issued at 332 PM EDT Thu Mar 13 2025

Isolated flash flooding is possible on Saturday night and Sunday
morning, as a severe thunderstorm squall line moves across the
region. The line will make steady progress eastward, limiting
duration of intense rainfall rates and therefore rainfall amounts.
Most places are forecast to get about 1-1.5 inches of rain, which
would generally not cause issues. However, if any parts of the
line temporarily slow down, then isolated flash flooding could
result.

Minor coastal flooding is possible along the shoreline of
Apalachee Bay on Saturday night and Sunday morning. Strong
southerly winds in advance of the Sunday cold front will push
water onshore, particularly along the north and northeast side of
Apalachee Bay. The normal tide cycle will be amplified this
weekend due to the upcoming full moon, so a lot will depend on if
the peak onshore push of water can overlap with the normal high
tide. Where these two occurrences overlap, then minor coastal
flooding would become a possibility.

&&

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   56  79  58  79 /  40   0   0  10
Panama City   61  76  63  76 /  10   0  10  30
Dothan        58  80  59  83 /  10   0  10  40
Albany        55  80  57  82 /  20   0   0  10
Valdosta      54  82  59  84 /  40   0   0   0
Cross City    52  82  56  83 /  40   0   0   0
Apalachicola  61  71  63  72 /  10   0   0  10

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&

NEAR TERM...LF
SHORT TERM...Haner
LONG TERM....Haner
AVIATION...LF
MARINE...Haner
FIRE WEATHER...LF
HYDROLOGY...Haner

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