Flash Flood Warning 17, NWS Tallahassee, FL

Area Forecast Discussion
National Weather Service Tallahassee FL
751 PM EDT Wed Apr 10 2024

...New AVIATION...

.NEAR TERM...
(Through Thursday)
Issued at 149 PM EDT Wed Apr 10 2024

Near: A large mid-upper trough will continue progressing across the
southeast with an attendant surface low currently situated over
western MS. This low should begin occluding to the northeast through
the remainder of today. Southeasterly flow is persisting and will
continue through the duration of the event advecting deep moisture
across the area. As the low occludes, a cold front will extend into
the CWA and serve as the primary forcing mechanism for storms
beginning this afternoon lasting through tomorrow afternoon. Two
rounds of severe are possible with this setup with the first being
the QLCS propagating toward our area and the second occurring
Thursday morning through the afternoon.

For the first part of this system beginning momentarily, the low-
level jet will continue strengthening as the upper trough amplifies
with 850mb winds reaching 70+kts. This will increase bulk shear
substantially across the area with values reaching 60-70kts out of
the west-southwest. Notably large looping hodographs are evident
across the area with high SRH nearing 400m2s2, perhaps higher
locally if surface winds remain out of the southeast. The main
caveat with this setup is instability with MLCAPE values seemingly
struggling to reach 500J/kg as a result of cooler midlevels. Sine
cloud breaks are evident, indicating that instability could rebound
somewhat ahead of the line. Regardless, a high-shear low-CAPE event
appears likely as low-level streamwiseness of the hodographs (0-3km)
is quite textbook, resulting in a tornado threat for the majority of
the area despite meager buoyancy. A couple strong tornadoes (EF-2+)
are also possible across our SE AL and FL Panhandle counties. A
damaging wind threat is also likely given the strong low-level wind
field with this system.

Storms will then dissipate as a brief lull in the LLJ takes place
before ramping up once again with 850mb winds in excess of 70kts as
the cold front traverses the area early tomorrow morning. Storms
will then reinvigorate along the cold front, perhaps maintaining
semi-discrete features as westerly effective shear in excess of
55kts overspreads the region. It appears that a frontal feature will
be lifting over the FL Panhandle and Big Bend as the MCS to the
north dissipates, resulting in instability increasing with MLCAPE
reaching around 1000-1500J/kg and SRH reaching around 400m2s2. This
is indicative of an increasing tornado threat, some possibly strong
(EF-2+), with a particular emphasis for our westernmost FL Panhandle
counties west of the Apalachicola River. A damaging wind threat and
perhaps some hail is also possible as lapse rates steepen with a
push of cooler air aloft steepening lapse rates.

A failure mode exists with the second round of storms. If the
antecedent convection to the north over our SE AL and SW GA counties
produce stronger outflow than forecast, the air farther south may
stabilize enough inland to inhibit convection substantially.
Regardless, an all-hazards threat exists across all of our counties
this afternoon through tomorrow afternoon, especially for our SE AL
and FL Panhandle counties.

WPC currently has all of our SE AL counties, portions of our SW
GA counties, FL Panhandle counties, and portions of our inland FL
Big Bend counties outlined in a Moderate Risk (3/4) for excessive
rainfall with nearly all of our CWA outlined in a Slight Risk
(2/4) for excessive rainfall, excluding the easternmost FL Big
Bend. More on this below in the Hydrology section.

Overnight lows will drop into the mid to upper 60s with highs
tomorrow in the upper 70s to low 80s.

&&

.SHORT TERM...
(Thursday night through Friday night)
Issued at 149 PM EDT Wed Apr 10 2024

Cold front and upper low exits eastward Thursday night with
surface high pressure translating from east Texas into southern
Alabama by Friday night. Decreasing clouds are on tap Thursday
night with sunshine plentiful Friday. Highs will be in the
mid/upper 70s Friday and lows in the upper 40s to lower 50s each
morning.

&&

.LONG TERM...
(Saturday through Tuesday)
Issued at 149 PM EDT Wed Apr 10 2024

Surface high pressure slides off the east coast this weekend while
mid level ridging builds across the eastern third of the US in
response to an upper low racing over the desert southwest at the
beginning of the next work week. Mid level flow will remain mostly
from the northwest, despite a mid level trough moving across the
midwest. The strength of the ridge will deflect the trough to the
north leaving fairly tranquil conditions in the extended. High
temperatures will reach for the mid/upper 80s early next week and
lows will bottom into the mid/upper 50s.

&&

.AVIATION...
(00Z TAFS)
Issued at 742 PM EDT Wed Apr 10 2024

Poor flying conds to continue for much of this TAF period thanks
to widespread SHRA/TSRA with embedded heavy rain, gusty winds,
and low cigs/vsbys (IFR-MVFR). Evening radar has the bulk of the
convection affecting ECP/DHN/ABY. Another round of storms is
expected overnight into the morning hrs and looks to pose a
severe threat from west to east ahead of a front. Used the latest
HRRR to help time the onset of +TSRA via tempo groups. Weather
improves tmrw after FROPA, but gusty west winds are expected.

&&

.MARINE...
Issued at 149 PM EDT Wed Apr 10 2024

A line of strong to severe thunderstorms is currently moving along
the southern Alabama Gulf coast into the coastal waters and is
moving eastward around 40 knots and is expected to reach our
coastal waters towards late afternoon west of Mexico Beach.
Strong winds, frequent lightning, and isolated waterspouts are
possible.

Southeast to south winds increase tonight in advance of a
vigorous cold frontal passage on Thursday. Southerlies are likely
to peak as gales tonight and early Thursday, or at least exhibit
frequent gale-force gusts. Following the cold frontal passage on
Thursday, a shift to strong westerlies is expected. Winds will
start to decrease on Thursday night, but it will take until
Saturday or Saturday night for the churned-up Gulf waters to
settle down. High pressure will pass east across the waters on
Saturday night.

&&

.FIRE WEATHER...
Issued at 149 PM EDT Wed Apr 10 2024

Storms are expected to exit the area by tomorrow afternoon
leaving a wetting rain behind. Following the passage of a cold
front, transport winds 25-30mph out of the west will overspread the
region tomorrow with mixing heights reaching up to 5000ft. This will
yield high to very high dispersions areawide tomorrow afternoon.
High dispersions areawide are also possible on Friday as elevated
transport winds persist out of the northwest. MinRH will drop to
around 40-60% tomorrow afternoon with 30-50% possible Friday.
Otherwise, there are no fire concerns at this time.

&&

.HYDROLOGY...
Issued at 149 PM EDT Wed Apr 10 2024

Potentially significant flash flood event expected to unfold
across the region this evening and into Thursday. Model guidance
has been fairly consistent in showing a corridor of 4-6 inches of
rain from the Florida Panhandle northeastward into Southwestern
Georgia. Isolated heavier amounts are anticipated to be as high as
8-9 inches in some spots, which if falling urban areas would lead
to considerable flash flooding. While these rainfall amounts are
most likely across the western half of the region, lighter amounts
of 2-4 inches are expected mainly east of the Flint/Ochlockonee
River basins and could still produce localized flash flooding. For
this reason nearly the entire region is under a flood watch.

In addition to the flash flood threat, riverine flooding will occur
in the days ahead. Should the widespread QPF verify, then we'd be
looking at the potential for moderate river flooding on our flashier
river basins like the Pea and Choctawhatchee Rivers in SE Alabama
and the Kinchafoonee Creek in Lee County GA. Depending on where the
rainfall develops further east, we could see minor riverine flooding
in the Ochlockonee, Apalachicola, and Withlacoochee Rivers as well.

For coastal flooding, opted to issue a coastal flood warning from
Wakulla County eastward to Dixie County. The tide around 4 am ET
Thursday morning is not quite aligned with the peak surge, so with
it being a bit offset, water levels may not get quite as high as
possible, but the strong winds behind the squall line will be
sufficient to produce enough surge combined with a higher high tide
around 2 pm ET to produce water levels of 2 to 4 feet above normally
dry ground within the warning area. A coastal flood advisory has
been issued for areas in Franklin County where water levels should
be slightly less.

&&

.SPOTTER INFORMATION STATEMENT...

Spotter activation is requested. Spotters should safely report
significant weather conditions and/or damage by calling the
office or tweeting us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...
Tallahassee   79  66  80  54 /  30 100  80   0
Panama City   76  66  74  58 /  70  90  20   0
Dothan        79  65  75  51 /  80 100  10   0
Albany        80  66  78  52 /  30  90  60   0
Valdosta      82  68  81  54 /  10  80  90   0
Cross City    82  66  77  55 /  10  30  90   0
Apalachicola  73  67  74  59 /  40  90  60   0

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through Thursday afternoon for FLZ007>019-026>028-
     108-112-114-115-118-127-128.

     Wind Advisory until 2 PM EDT /1 PM CDT/ Thursday for FLZ011-013-
     016>019-026.

     Wind Advisory until 11 AM EDT /10 AM CDT/ Thursday for
     FLZ007>010-012-014-015-027-114-115-118-127.

     Wind Advisory from 2 AM to 2 PM EDT Thursday for FLZ028-029-034-
     128-134.

     High Rip Current Risk through late Friday night for FLZ108-112-
     114-115.

     High Surf Advisory until 5 AM EDT /4 AM CDT/ Friday for FLZ108-
     112-114.

     Wind Advisory until 10 AM CDT Thursday for FLZ108-112.

     Coastal Flood Advisory until 8 PM EDT Thursday for FLZ115.

     High Surf Advisory from 2 AM to 2 PM EDT Thursday for FLZ115.

     Coastal Flood Warning until 8 PM EDT Thursday for FLZ118-127-128-
     134.

GA...Flood Watch through Thursday afternoon for GAZ120>131-142>148-
     155>161.

     Wind Advisory until 2 PM EDT Thursday for GAZ123-125-127>131-
     142>148-155>161.

AL...Flood Watch through Thursday afternoon for ALZ065>069.

     Wind Advisory until 1 PM CDT Thursday for ALZ068-069.

GM...Gale Warning until 3 PM EDT Thursday for GMZ730-755-765-775.

     Gale Warning until 10 AM CDT Thursday for GMZ750-752-770-772.

&&

NEAR TERM...Worster
SHORT TERM...Scholl
LONG TERM....Scholl
AVIATION...IG3
MARINE...Scholl
FIRE WEATHER...Worster
HYDROLOGY...Godsey

Preliminary Local Storm Report
National Weather Service Tallahassee FL
704 PM EDT Wed Apr 10 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0653 PM     Tstm Wnd Gst     5 NE West Bay           30.35N 85.80W
04/10/2024  M49 MPH          Bay                FL   ASOS

            ASOS station KECP Panama City reported a
            wind gust of 49 MPH.

&&

KO

Preliminary Local Storm Report
National Weather Service Tallahassee FL
725 PM EDT Wed Apr 10 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0600 PM     Tstm Wnd Dmg     1 NE Dothan             31.23N 85.38W
04/10/2024                   Houston            AL   911 Call Center

            911 Call Center reported a tree down at
            Beulah and Webb.

&&

KO

Preliminary Local Storm Report
National Weather Service Tallahassee FL
748 PM EDT Wed Apr 10 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0600 PM     Tstm Wnd Dmg     2 NNW Webb              31.29N 85.29W
04/10/2024                   Houston            AL   911 Call Center

            Corrects previous tstm wnd dmg report from 1
            NE Dothan. 911 Call Center and EM reported a
            tree down at Bill Yance Rd in Webb across
            both lanes.

&&

KO

Preliminary Local Storm Report
National Weather Service Tallahassee FL
818 PM EDT Wed Apr 10 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0540 PM     Tstm Wnd Dmg     3 E Santa Rosa Beach    30.39N 86.17W
04/10/2024                   Walton             FL   Dept of Highways

            Florida Highway Patrol live traffic report
            indicates power lines are down and the Clyde
            B Wells bridge is currently shut down.

&&

KO

Preliminary Local Storm Report
National Weather Service Tallahassee FL
850 PM EDT Wed Apr 10 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0840 PM     Flash Flood      1 SW Rehobeth           31.12N 85.45W
04/10/2024                   Houston            AL   Emergency Mngr

            EM reported two roads with 3-4 inches of
            water running across them in Rehobeth, AL in
            Houston County.

&&

KO

Preliminary Local Storm Report
National Weather Service Tallahassee FL
855 PM EDT Wed Apr 10 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0840 PM     Flash Flood      1 ESE Gulf Resort Beach 30.21N 85.87W
04/10/2024                   Bay                FL   Emergency Mngr

            EM reported water on the road near a
            construction site along Front Beach Rd.

&&

KO