Special Marine Warning 39, NWS Tallahassee, FL

Area Forecast Discussion
National Weather Service Tallahassee FL
214 AM EST Thu Feb 18 2021

.NEAR TERM [Through Tonight]...

The central CONUS longwave trough will gradually make eastward
progress today, forcing a frontal system into the Tri-State region.
The shortwave responsible for cyclogenesis in the western Gulf is
moving through the Midwest this morning, with an associated surface
boundary draped down the Appalachians to the surface low near the
mouth of the Mississippi. Late this afternoon through the overnight
hours, another shortwave will rotate through the base of the trough
and provide support for anafrontal rain and possibly elevated
thunderstorms before eventually forcing the entire frontal system
out of the region on Friday.

VAD wind data support model analysis of a large low-level jet across
the southeast associated with the surface low and latent-heat
release along the aforementioned boundary. For the moment, low-level
winds are backed ahead of the approaching surface low, but are
forecast to quickly transition to a more uni-directional regime
through the column as the low pulls northeast and the surface
boundary temporarily stalls across the region waiting on the arrival
of the secondary shortwave. This set-up would favor a greater
tornado potential this morning, followed by a greater threat for
damaging winds later this afternoon. This morning's convection will
have to fight the nocturnal inversion as it moves inland along the
Panhandle coast - at least until the airmass modifies enough to
support surface based convection. Nonetheless, isolated to scattered
storms will carry the potential for a tornado or damaging winds this
morning, especially along the immediate coast. Then, towards the
afternoon the threat for severe weather will spread inland and
transition to more of a damaging wind and possible hail potential,
with the overall severe potential lowering through the day.

Patches of rain will continue through the night associated with the
second wave, with slowly cooling temperatures behind the front.
Expect overnight lows to fall into the lower 40s across southeast
Alabama, but remain in the lower 60s in the extreme southeast Big
Bend.

.SHORT TERM [Friday Through Saturday]...

In the upper levels, a trough will move through the region Friday
and Friday night. On Saturday, nearly zonal flow will be in place.
At the surface, a cold front will be just southeast of the region
Friday morning. High pressure and a cool, dry air mass will move in
Friday afternoon/evening. Rain will linger behind the frontal
boundary Friday morning, especially east of a line from Albany,
Georgia to Tallahassee. By Friday afternoon, rain will be confined
to the Eastern Big Bend Counties and clouds will begin to clear out
in the west. POPs will be near zero Friday night and Saturday with
clear/sunny skies. Highs will be mainly in the 50s Friday and
Saturday. Lows Friday night will be in the 30s with freezing temps
expected for Southeast Alabama, Panhandle Florida (away from the
immediate coast), and much of Southwest Georgia.

.LONG TERM [Saturday Night Through Thursday]...

In the upper levels, nearly zonal flow will be over the region until
a shortwave moves through on Monday night. Nearly zonal flow will
return midweek and a ridge will build in late in the week. At the
surface, high pressure will be over the region Sunday. Southerly low
level flow will return on Sunday and another cold front will move
through on Monday. This weak cold front will likely be a dry frontal
passage with only a slight chance of rain forecast. Otherwise, this
forecast period will be dry. Highs will be in the 60s. Lows will be
in the 30s and 40s.

&&

.AVIATION...
[Through 06Z Friday]

Conditions will deteriorate to IFR/LIFR through the night, with
light rain or drizzle for most areas. Near sunrise, a line of
thunderstorms will near ECP and DHN and then move eastward through
the day. Behind this line a band of rain and possibly a few
thunderstorms will fill in and move east behind the initial line
through the remainder of the afternoon and evening hours. VFR is not
forecast during the TAF period.

&&

.MARINE...

Strong southerly winds will become northerly tonight as a cold front
moves through the region. A Small Craft Advisory is in effect until
Saturday morning. This weekend winds will be moderate and northerly
on Saturday and easterly on Sunday. Strong to severe storms will be
possible today. Dry weather is expected next week.

&&

.FIRE WEATHER...

Once the rain comes to an end on Friday, dry conditions will prevail
through the weekend. Red Flag conditions are not expected,
however.

&&

.HYDROLOGY...

Most local rivers are rising and many are in action or flood stage.
The Apalachicola River near Blountstown is in flood stage. The
Ochlockonee River is in minor flood stage near Thomasville and
Havana and in moderate flood stage near Concord. The Withlacoochee
River is in flood stage near Valdosta, Quitman and Foxborough.

Another slow moving system will bring rain (heavy at times) Thursday
through Friday morning. Forecast rainfall totals through Friday are
1 to 2.5 inches but stronger storms will produce locally higher
amounts up to 3 to 4 inches. River flooding will likely be worse by
this weekend. A Flash Flood Watch is in effect for all of the
Southwest Georgia Counties.

&&

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur (while following all local, state, and CDC guidelines) by
calling the office or tweeting us @NWSTallahassee.

&&

.PRELIMINARY POINT TEMPS/POPS...

Tallahassee   73  49  57  33  58 /  80  80  50   0   0
Panama City   70  46  56  34  58 /  90  80  20   0   0
Dothan        66  41  52  29  55 /  80  70  20   0   0
Albany        70  45  54  31  55 /  90  90  40   0   0
Valdosta      76  49  56  34  56 /  70  80  60   0   0
Cross City    78  57  64  36  61 /  30  70  70   0   0
Apalachicola  69  49  57  36  58 /  70  70  40   0   0

&&

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

GA...Flash Flood Watch through Friday morning for Baker-Ben Hill-
     Berrien-Brooks-Calhoun-Clay-Colquitt-Cook-Decatur-Dougherty-
     Early-Grady-Irwin-Lanier-Lee-Lowndes-Miller-Mitchell-
     Quitman-Randolph-Seminole-Terrell-Thomas-Tift-Turner-Worth.

AL...None.
GM...Small Craft Advisory until 7 AM EST /6 AM CST/ Saturday 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.

     Small Craft Advisory until 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.

&&

NEAR TERM...Harrigan
SHORT TERM...McD
LONG TERM...McD
AVIATION...Harrigan
MARINE...McD
FIRE WEATHER...Harrigan
HYDROLOGY...McD