Severe Thunderstorm Warning 121, NWS Tallahassee, FL

Area Forecast Discussion
National Weather Service Tallahassee FL
648 AM EDT Thu Apr 13 2023

...New AVIATION...

.NEAR TERM...
(Today through Friday) Issued at 348 AM EDT Thu Apr 13 2023

An upper low and attendant surface low will continue to lift out
of the Gulf of Mexico this morning into the afternoon. Additionally,
the associated warm front will continue to lift north across the
CWA as the day progresses beginning with a large swath of stratiform
rain before bringing strong to severe storms across the area with
the main hazards being a few tornadoes and damaging wind gusts.

Much of the area has been upgraded to a Slight Risk via the SPC
with the entire CWA inside a 2% tornado threat and a 5% tornado
threat encompassing most of our SW GA counties. A 15% damaging
wind risk has also been outlined over just about the entire CWA.
In the morning hours as the surface low moves onshore, a triple
point feature appears to develop which may generate enough forcing
for a few storms to form near our western FL Panhandle counties.
In addition, low level shear will be noticeably higher versus
other areas within the CWA due to surface wind backing near the
triple point region which is evident in the hodographs and
localized 0-1km SRH ranging from 200-300m2/s2. However, this may
be short lived as models depict the instability advecting north at
a slow pace resulting in the storms either maturing briefly
before encountering stable air or struggling to mature as a whole.
Regardless, a brief tornado appears possible in our FL Panhandle
Counties.

In our SE AL and SW GA counties, the environment will be much more
favorable for severe storms in the afternoon and early evening
hours. Models indicate a large area across our SW GA counties into
our SE AL counties where 3CAPE ranges from 100-200J/kg with 0-3km
LR's averaging around 7.5C/km. However, despite the small hodograph
size, they remain quite curved in the lower levels generating 0-3km
SRH values around 100-200m2/s2 and 0-3km bulk shear around 25kts.
Supercells appear possible in this environment with a few tornadoes
possible.

Isolated showers and thunderstorms appear possible into the evening,
though coverage will be quite limited. Surface winds will clock to
southwesterly through Saturday morning which will help retain some
moisture in the area. Upper ridging will build back in and mix out
the clouds, bringing in clearer skies come Friday evening.

&&

.SHORT TERM...
(Friday night through Saturday night)
Issued at 348 AM EDT Thu Apr 13 2023

Weak upper level ridging is forecast for Saturday but will
gradually be pushed out of the region as a trough over the MS
River Valley moves east. Ahead of this trough, models depict a
shortwave that forms over the Gulf. Current forecast suggests much
of the region will remain dry through the morning, with chances
for showers and thunderstorms possible for SE AL, the FL
Panhandle, and the W portion of the FL Big Bend. NBM seemed to do
a decent job highlighting the possibility of precipitation since
no model or ensemble has the same solution.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 348 AM EDT Thu Apr 13 2023

Ensembles and guidance show a trough and associated cold front
moving through the SE on Sunday. This should bring a decent shot
at showers and thunderstorms to the region. Guidance doesn't look
too favorable for severe weather at this time, but we're starting
to get in range of the CAMs so that could change. Behind the
front, high pressure returns leading to dry weather for the first
half of the work week. Cooler overnight temperatures will be
briefly observed as lows 40s and 50s. Highs bounce from the upper
70s to low 80s Sunday, to the mid to upper 70s on Monday, and then
back into the upper 70s to mid 80s for Tuesday and Wednesday.

&&

.AVIATION...
(12Z TAFS)
Issued at 648 AM EDT Thu Apr 13 2023

Winds will start the period southeasterly and continue to
clock to southerly into the evening tonight. Vis will drop
periodically across all sites as showers and thunderstorms will
impact all sites throughout the day with ceilings dropping to
borderline IFR CIG's. Some sites such as KTLH, KVLD, and KECP may
drop to IFR however it has been left above due to some uncertainty.
MVFR conditions are currently being observed across all sites as
ceilings continue to drop. Conditions at all sites will briefly
improve at 00Z, however dense fog is possible across all sites early
Friday morning. There is uncertainty in how dense the fog may be
given surface winds may be slightly higher than what is depicted at
the moment.

&&

.MARINE...
Issued at 348 AM EDT Thu Apr 13 2023

Winds are gradually switching to the south via buoy 42039 but are
still producing gale force gusts. Expect winds to fall to high end
Small Craft Advisory near daybreak with occasional gales gusts
occuring for a bit. For the rest of today, bands of thunderstorms
are forecast, with potential for brief wind gusts to 50 knots and
waterspouts. Winds and seas will more quickly decrease later in
the day with winds generally remaining light and southerly through
the weekend. A cold front will move across the waters on Sunday.

&&

.FIRE WEATHER...
Issued at 348 AM EDT Thu Apr 13 2023

Deep moisture associated with an incoming surface low will
spread over the region today. Scattered showers and thunderstorms
will occur across the entire area today into the morning on Friday.
High dispersions are expected today in our FL Panhandle counties, SE
AL counties, and our south-central GA counties. High dispersions
across the entire area will also be possible on Friday.

&&

.HYDROLOGY...
Issued at 348 AM EDT Thu Apr 13 2023

The rain forecast has decreased again with rain abouts generally
ranging from 0.40 to 0.80 inches of rain along and west of the
Apalachicola and Flint rivers while areas east are generally
around 0.25 to 0.75. The exception being Taylor, Lafayette, and
Dixie counties where amounts range from 0.00 to 0.25 inches of
rain. The Excessive Rainfall Outlook from WPC has been trimmed
back as a result removing the SE FL Big Bend from the Marginal
Risk. There is still quite a bit uncertainty that we will get any
flooding as it heavily depends on how the bands of showers and
thunderstorms set up today. This could lead to nuisance flooding
and perhaps very localized flash flooding. Confidence remains low
on timing and placement of precipitation bands.

The next chance for rain arrives late into the weekend as a weak
shortwave trough followed by a cold front moves through the
region. This may bring some showers and thunderstorms to the
region but there are no flooding concerns with this system at this
time.

Rivers remain in good shape.

A note on coastal flooding, the area of concern is Apalachicola.
Tides peaked around 1.02 feet today and seemed to have a 2.3 ft
anomaly couple of hours ago. If this remains around 2 feet we
could see minor coastal flooding at Apalachicola later this
afternoon. Confidence is low but it will need to be something to
watch as winds shift from the east to the southeast and south.

&&

.SPOTTER INFORMATION STATEMENT...

Spotter activation is requested. Spotters should safely report
significant weather conditions and/or damage (while following all
local, state, and CDC guidelines) by calling the office or tweeting
us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   80  62  81  58 /  80  20  10   0
Panama City   77  65  76  64 /  80  40   0   0
Dothan        77  59  77  55 /  90  30  10   0
Albany        78  59  77  57 /  90  50  10   0
Valdosta      81  62  80  58 /  90  20  10   0
Cross City    83  63  80  59 /  50  20  10   0
Apalachicola  76  66  75  65 /  70  30   0   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through late tonight for FLZ108-112-114-
     115.

GA...None.
AL...None.
GM...Small Craft Advisory until 8 AM EDT this morning for GMZ730-765.

     Small Craft Advisory until 11 AM EDT /10 AM CDT/ this morning
     for GMZ750-752-755-770-772-775.

&&

NEAR TERM...Worster
SHORT TERM...KR
LONG TERM....KR
AVIATION...Worster
MARINE...KR
FIRE WEATHER...Worster
HYDROLOGY...KR

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