Special Marine Warning 33, NWS Tallahassee, FL

Area Forecast Discussion
National Weather Service Tallahassee FL
1152 AM EST Mon Feb 15 2021

...ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO THIS
EVENING WITH DAMAGING WINDS AND A FEW TORNADOES POSSIBLE...

.UPDATE...

Squall line is taking shape to our southwest over the Gulf of
Mexico and current trends agree with the timing of the arrival
as early as 2 PM over SE AL and the Western FL Panhandle. Despite
the cool air mass this morning, the warm front is expected to
move rapidly north this morning and lead to sufficient instability
for severe thunderstorms. Please be weather aware this afternoon/
evening and have a way to receive warnings!

&&

.PREV DISCUSSION [1036 AM EST]...

.NEAR TERM [Through Tonight]...

Dramatic changes will take place over the next 24 hours as a very
dynamic system moves through the area. Currently across the area,
the boundary layer is cool and stable with light northerly surface
flow and temperatures in the 40s and 50s. However, looking out
across the Gulf, the oil platforms south of New Orleans currently
have mid 60s dewpoints, and this airmass will advect rapidly
northeastward later this afternoon ahead of a strong cold front and
wave of low pressure. The 00z NAM, GFS, and ECMWF all have mid 60s
dewpoints reaching into southern Georgia by the end of the day. This
is the key for the upcoming severe weather threat as instability is
the big question mark. Both low level and deep layer shear will be
plentiful with a strong low level jet and favorable upper level jet
dynamics. A strongly forced squall line is expected to develop west
of the area and rip across the area rapidly from west to east from
the mid afternoon hours through the evening hours. Assuming the
guidance is right that sufficient instability will return northward
ahead of it, then scattered severe weather seems like a decent bet
along the squall line with damaging winds and a few tornadoes
possible.

Behind the front, much colder air will briefly penetrate into
portions of southeast Alabama and adjacent counties late tonight
with lows possibly dipping into the mid 20s and wind chills dipping
into the upper teens.

.SHORT TERM [Tuesday Through Wednesday]...

A brief break from the persistent wet pattern is in store throughout
the short term. In the wake of Monday's frontal passage, our region
will experience a short period of CAA as winds become northwesterly.
This will bring clear skies through Wednesday morning with dewpoints
in the lower 30s. However, this is short lived, throughout Wednesday
afternoon winds transition to being easterly, cloud cover increases,
and dewpoints begin their climb ahead of the next frontal system on
Thursday. Overnight lows will be in the low to mid 30s across
most of the region, with only the FL Big Bend reaching the low
40s. Daytime highs on Tuesday will be in the upper 40s across SE
AL and around 60 across the SE FL Big Bend. On Wednesday highs
will generally be in the low to mid 60s.

.LONG TERM [Wednesday Night Through Monday]...

Throughout Wednesday night into Thursday morning we'll transition
from easterly flow back into southeasterly flow ahead of the next
frontal system on Thursday. In the process we'll see some impressive
return flow as dewpoints recover quickly from the last frontal
passage. Dewpoints will be going from the mid 40s to the mid 60s
across our northern counties between Wednesday evening and
Thursday afternoon (~18 hours). Throughout the day on Thursday a
piece of energy digs deep into the central plains allowing the
longwave trough trapped over the central US to finally budge. This
PV energy will move eastward bring with it enhanced upper level
support, through PVA, while putting our region under the right
entrance region of an upper level jet streak. In the lower levels,
the GFS has remained consistent with the placement of a 50-65 kt
LLJ across our CWA through frontal passage. Additionally, with
dewpoints in the mid to upper 60s and CAPE around 500-1000 J/kg
ahead of the front, all of the ingredients are present for the
potential for severe weather. The limiting factor here could
potentially be the lack of robust midlevel lapse rates. Once this
front exist the region Friday morning, we'll be freed from the wet
pattern that has dominated for the last week or so. We'll enter a
cool and dry period with mostly sunny skies through the rest of
the long term as we head into zonal flow.

Expect overnight lows to rebound after frontal passage. Overnight
lows will range from the mid 50s (before passage) to the lower 30s
(after passage), rebounding into the mid 40s by Monday morning.
Daytime highs will experience a similar pattern and will range from
the mid 70s (before passage) to the low to mid 50s (after passage),
rebounding into the upper 60s by Monday afternoon.

.AVIATION...

[Through 12z Tuesday] IFR to LIFR conditions will prevail through
most of the period with low ceilings and areas of fog. The
visibilities will improve later this morning, but the low ceilings
will persist. For late this afternoon into this evening, a squall
line of thunderstorms will race through the area ahead of a cold
front with gusty winds likely.

.MARINE...

As a cold front makes its way across our region this afternoon a
small craft advisory will go into effect until tomorrow morning.
Post-frontal passage, we'll experience a brief break in
precipitation through Wednesday afternoon. Winds and seas will
likely reach SCA criteria again ahead of the next frontal system on
Thursday.

.FIRE WEATHER...

Red flag conditions are not expected for the next several days.

.HYDROLOGY...

River flood warnings are in effect for the Withlacoochee above
Valdosta, the Ochlockonee River Concord (CR 12) and Thomasville (US
84), and the Apalachicola River near Blountstown.

Rainfall amounts over the next week will range from 1 to 3 inches
from the SE FL Big Bend (lower) to Southeast AL (higher). This will
occur from the next two storm systems on Monday and Thursday, and
could aggravate river flooding.

For more detailed information on specific river stages and
forecasts, visit: http://water.weather.gov/ahps2/index.php?wfo=tae.

.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   69  39  55  34  60 /  70  90   0   0  40
Panama City   66  32  52  35  63 /  90  30   0   0  30
Dothan        64  26  46  29  56 /  90  40   0   0  30
Albany        64  32  50  31  56 /  80  90   0   0  30
Valdosta      70  42  56  35  59 /  50  90   0   0  40
Cross City    74  51  62  39  67 /  50  90  10   0  50
Apalachicola  68  42  54  39  64 /  70  90   0   0  40

&&

.TAE WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Tuesday evening for Coastal Bay-
     Coastal Franklin-Coastal Gulf-South Walton.

GA...None.
AL...None.
GM...Small Craft Advisory from 4 PM this afternoon to 10 PM EST this
     evening for Apalachee Bay or Coastal Waters From Keaton
     Beach to Ochlockonee River FL out to 20 Nm-Coastal waters
     from Suwannee River to Keaton Beach FL out 20 NM.

     Small Craft Advisory until 7 AM EST /6 AM CST/ Tuesday for
     Coastal Waters From Ochlockonee River to Apalachicola Fl
     out to 20 Nm-Coastal waters from Mexico Beach to
     Apalachicola FL out 20 NM-Coastal waters from Mexico Beach
     to Okaloosa Walton County Line FL out 20 NM-Waters from
     Suwannee River to Apalachicola FL from 20 to 60 NM-Waters
     from Apalachicola to Mexico Beach FL from 20 to 60 NM-
     Waters from Mexico Beach to Okaloosa Walton County Line FL
     from 20 to 60 NM.

&&

UPDATE...LF
NEAR TERM...DVD
SHORT TERM...Oliver
LONG TERM...Oliver
AVIATION...DVD
MARINE...Oliver
FIRE WEATHER...DVD
HYDROLOGY...LF/Oliver