Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 232025
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
325 PM EST Mon Jan 23 2017

...Windy Conditions to Gradually Subside Overnight...

.Currently...
Afternoon surface analysis depicts an occluded strong low
pressure center (990 millibars) extending from the Appalachians to
the Virginia Capes. Weak high pressure was building into the
Plains states and lower Mississippi Valley in the wake of this
system. Aloft...the axis of a deep, negatively tilted trough is
has passed the Florida peninsula, with deep northwest flow over
our region in its wake. Wrap-around moisture and a PVA spoke are
creating an area of light showers over portions of southeast
Georgia, with measurable light rainfall occurring for locations
from Waycross north and eastward. Cold advection stratocumulus
blankets our region, but the back edge of this moisture is pushing
into western Georgia and the Florida panhandle, where skies are
clearing. Mostly cloudy skies and modest cold air advection has
kept temperatures today generally between 60-65 degrees, with
dewpoints generally in the 50s.

.Near Term (Tonight and Tuesday)...
The slow northward movement of the low pressure center near the
Mid-Atlantic coast will keep a tight local pressure gradient in
place through tonight. Westerly surface winds of 20-30 mph with
occasional gusts up to 40 mph will continue through sunset, and
thus a wind advisory remains in place area-wide through 6 PM.
Skies will clear from west to east during the evening hours.
Breezy winds will persist overnight and will become
northwesterly during the predawn hours, with lows falling into the
40s region-wide.

Flat ridging aloft will build into our region from the west on
Tuesday, with weak high pressure shifting southeastward from the
lower Mississippi Valley to the eastern Gulf of Mexico. Our local
pressure gradient will continue to loosen, with west northwest
surface winds decreasing to 10-15 mph by the late morning hours.
Full sunshine will counter weak cool air advection, with highs
reaching the mid and upper 60s for most locations, which is near
or slightly above late January climo.

.Short Term (Tuesday Night through Wednesday Night)...
High pressure will shift southward to a position over south FL
Tuesday night, with radiational cooling expected over northeast
FL. Meanwhile, the next trough aloft and associated cold front
resulting in southwest winds developing overnight for southeast
GA. Lows will fall into the 40s region-wide. High cloudiness will
increase ahead of the approaching cold front on Wednesday, but
rising heights and gradually deepening southwesterly flow will
boost highs into the mid 70s. The front will advance eastward
through the Florida panhandle and western Georgia on Wednesday
night. Low stratus may advect northward from the Gulf of Mexico
ahead of this front over north central and portions of northeast
Florida during the overnight hours. Showers will be possible after
midnight over southeast Georgia and the western Suwannee Valley.
Lows will run about 15 degrees above late January climo, with
55-60 expected for most locations.

.Long Term (Thursday through Sunday)...
Another frontal system will move through the area on Thursday
morning and afternoon. Weak southwesterly flow ahead of the cold
front will allow an increase in moisture, with low 60s dewpoints
returning to the area. There is a fair amount of shear, but
instability looks rather weak even during peak heating. A few
rumbles of thunder are possible mainly in the Suwannee Valley
early and the Coastal waters Thursday afternoon/evening. Dry
northwesterly flow will remain across the area for most of the
weekend, with a large upper level low across Canada forcing a few
shortwave troughs and weak cold fronts across the Midwest and into
the Southeastern US. The big story with this system will mainly be
the change coming in the form of temperatures. High temperatures
Friday onward may struggle to reach the 60s in most locations,
with low temperatures in the mid 30s across all but the far
southern zones. Frost and/or light freezes could be possible
across SE Georgia and far northern FL. Chances for showers could
return on Sunday, but for now, looks like any precip will remain
just along the far southern zones in Florida.

&&

.Aviation...
MVFR cigs from 1500-2000 feet, accompanied by a few light showers,
are anticipated at SSI through 23Z. Occasional MVFR ceilings of
2500-3000 feet will be possible at the Duval County terminals
through 00Z, with VFR ceilings of 3000-3500 feet expected at CRG
and SGJ. VFR conditions are expected at the regional terminals
after 00Z. Strong westerly winds will continue at the regional
terminals through around 03Z, with sustained speeds near 20 knots
and occasional gusts to 35 knots. Surface winds will become
northwesterly tonight, with speeds at GNV and VQQ decreasing to
10-15 knots with occasional gusts up to 20 knots. Stronger winds
sustained at near 15 knots will continue at SSI...SGJ...JAX...and
CRG overnight.

&&

.Marine...
Double barreled low pressure extending from the Appalachians to
the Virginia capes will move slowly northward along the Mid-
Atlantic and New England coasts tonight and Wednesday. A very
tight local pressure gradient will keep strong offshore winds in
place through tonight. A Gale Warning remains in effect for the
offshore waters beyond 20 nautical miles through tonight, where
frequent gusts to around 35 knots. A small craft advisory
continues for the near shore waters, where offshore winds will
occasionally gust to 35 knots early this evening. Offshore winds
will subside to Small Craft Advisory range (20-25 knots) in the
offshore waters on Tuesday, with caution conditions (15-20 knots)
expected near shore. Our local pressure gradient will rapidly
loosen by Tuesday afternoon and evening as weak high pressure
builds over the Florida peninsula. Winds and seas will subside
below caution levels by Tuesday night throughout the coastal
waters.

Offshore winds will increase in advance of the next cold
front on Wednesday night, with southwest winds increasing to small
craft advisory levels offshore and caution conditions near shore.
Small craft advisory conditions will continue offshore through the
frontal passage around noon on Thursday, and will then subside
slightly to caution levels by Thursday afternoon as winds become
northwesterly. Winds in the near shore waters will increase to
caution levels on Wednesday night and early Thursday in advance of
the front, falling to just below caution levels by late Thursday
in the wake of the front.

Rip Currents: Low risk due to strong offshore winds through
Tuesday. A long period ocean swell may create a moderate risk by
Wednesday.

&&

.Hydrology...
River Flood Warning issued for the Altamaha River near Baxley,
with possible warnings to come for more locations on the Altamaha
River, Satilla River and Alapaha River this week as heavy rains
drain into the SE GA river basins.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  45  67  43  74 /   0   0   0   0
SSI  47  66  49  70 /   0   0   0   0
JAX  47  69  46  74 /   0   0   0   0
SGJ  50  69  48  74 /   0   0   0   0
GNV  46  69  43  75 /   0   0   0  10
OCF  47  69  45  76 /   0   0   0   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory until 6 PM EST this evening for Alachua-Baker-
     Bradford-Clay-Coastal Duval-Coastal Nassau-Columbia-Flagler-
     Gilchrist-Hamilton-Inland Duval-Inland Nassau-Marion-Putnam-
     St. Johns-Suwannee-Union.

GA...Wind Advisory until 6 PM EST this evening for Appling-Atkinson-
     Bacon-Brantley-Charlton-Clinch-Coastal Camden-Coastal Glynn-
     Coffee-Echols-Inland Camden-Inland Glynn-Jeff Davis-Pierce-
     Ware-Wayne.

AM...Gale Warning until 4 AM EST Tuesday for Waters from Altamaha
     Sound GA to Fernandina Beach FL from 20 to 60 NM-Waters
     from Fernandina Beach to St. Augustine FL from 20 to 60 NM-
     Waters from St. Augustine to Flagler Beach FL from 20 to 60
     NM.

     Small Craft Advisory until 4 AM EST Tuesday for Coastal waters
     from Altamaha Sound to Fernandina Beach FL out 20 NM-
     Coastal waters from Fernandina Beach to St. Augustine FL
     out 20 NM-Coastal waters from St. Augustine to Flagler
     Beach FL out 20 NM.

&&

$$

Nelson/Elsenheimer/Peterson



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