Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 171000
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
500 AM EST Tue Jan 17 2017

...Dense Fog Advisory through Mid-Morning for Most of Southeast
Georgia and Portions of Northeast Florida...

.Currently...
Early morning surface analysis depicts high pressure (1027
millibars) centered off the Mid-Atlantic coast. A frontal boundary
is wedged along the Appalachians to the southwest of this surface
ridge. Meanwhile, a cold front extends from the western Great
Lakes southward to the lower Mississippi River Valley.
Aloft...robust ridging remains centered near Mexico`s Yucatan
peninsula, which has deflected a potent shortwave northeastward
into the Great Lakes region. Patches of high cirrus clouds are
streaming eastward along the northern Gulf Coast states. Dense fog
covers much of southeast Georgia, with sea fog remaining in place
over the adjacent coastal waters. Dense fog is in place over
portions of northeast Florida, with fair skies for most of north
central Florida. Temperatures and dewpoints as of 09Z generally
range from 55-60, except 50-55 over north central Florida.

.Near Term (Today through Wednesday)...
Our region will remain under the influence of the deep-layered
ridge centered over the northwestern Caribbean Sea through
Wednesday. This ridge will flatten somewhat by late Wednesday as a
shortwave trough currently near the western Great Lakes pivots
eastward and moves off the Mid-Atlantic coast. In response to this
pattern, surface ridging will shift southward over the western
Atlantic waters, causing our local winds to gradually veer
tonight and Wednesday. A dry and subsident air mass will prevail
through tonight, with fog being the main forecast challenge. High
resolution short term guidance suggests that fog currently
blanketing southeast Georgia and the Interstate 10 corridor in
northeast Florida will expand southward down the St. Johns River
basin early this morning. Fog should dissipate over most locations
by the mid-morning hours, with lingering sea fog possible over
coastal southeast Georgia through noon. Sea fog may linger
throughout the day over the near shore Georgia waters. Once fog
dissipates this morning, unseasonable warmth will continue over
our region under mostly sunny skies, with periods of high cirrus
advecting over our area from the west and a flat cumulus field
developing this afternoon. Inland highs will be near 80, which is
15-20 degrees above mid-January climo. The daily record at Alma,
set on this date in 1949, will be in jeopardy.

A light southwesterly flow in the low levels may promote fog
formation over inland areas initially during the overnight hours,
with fog likely advecting into coastal locations during the
predawn hours. Sea fog may also linger over the near shore
Georgia waters as dewpoints remain near or slightly above surface
water temperatures, or around 60 degrees. Periods of mostly thin
cirrus will continue to move eastward through our region
overnight, but this should not impact fog formation
significantly. Lows will again only fall to the 50s, which is
10-15 degrees above mid-January climo.

A frontal boundary will push into the southeastern states on
Wednesday. This boundary will likely stall just to the north of
the Altamaha/Ocmulgee Rivers as shortwave energy departs eastward
off the Mid-Atlantic coast. Meanwhile, another shortwave will
eject northeastward from the desert southwest into the southern
Plains states. This weather pattern will induce a deepening
southwesterly wind regime locally, with deeper moisture advecting
over our region from the west during the afternoon. The front
moving into Georgia may provide just enough forcing to support
isolated shower development over inland southeast Georgia during
the afternoon hours. Otherwise, not much change will occur, with
early morning fog dissipating and a deeper afternoon cumulus
field perhaps resulting in highs just a degree or two cooler than
today.

.Short Term (Thursday through Saturday)...
Thursday will likely be our last dry day as the upper level
pattern starts to shift. Heights begin falling in response to an
upper level low across the Central US. A weak shortwave will cross
the area Thursday night and begin our chances for precipitation.
With little to no instability, this will likely just remain just
showers, and will probably be confined mostly to the FL Panhandle
and Southern Georgia. On Friday, chances dip a bit further south
into NE Florida as heights fall with a shortwave trough crossing
the Tennessee Valley. Despite heights rising some on Saturday, the
pattern continues to be unsettled through the weekend. A warm
front looks to setup along the FL/GA border, and southwesterly
flow aloft will keep a steady stream of moisture in place.
Thunderstorms look pretty likely as surface based CAPE values are
near 1000 J/kg during the afternoon hours. 0-6km Bulk shear values
of around 40 to 50kts, and a weak shortwave could be enough for
some strong to severe thunderstorms.

.Long Term (Sunday through Tuesday)...
Heights will fall rapidly on Sunday as a very deep upper level
trough approaches the region and a surface low pressure system
develops across the southern Mississippi Valley. Models in pretty
good agreement with the development of this system, and its track
across the Southeast. Widespread rainfall and scattered
thunderstorms are possible as the cold front moves into SE Georgia
and NE Florida sometime on Monday. Right now, it appears there
will be a fair amount of shear (50-70kts of 0-6km Bulk Shear) as
the upper level trough passes through and a fair amount of
moisture off the Gulf out ahead of the front. The models still
differ some on the timing though, and that could make the
difference as to whether there will be enough instability for more
of a thunderstorm event rather than just widespread rainfall. High
temperatures on Tuesday will likely be below normal (mid 60s), but
this cooler weather will likely be rather short lived as upper
level ridging begins to build again behind the trough.

&&

.Aviation...
VLIFR conditions will prevail through 13Z at SSI and the Duval
County terminals. VLIFR conditions are expected to develop at SGJ
and GNV between 10Z-11Z, and should persist through around 13Z.
Conditions should improve to IFR by 14Z, with VFR conditions
expected at the northeast Florida terminals by 15Z. Confidence is
lower in visibility improvements at SSI during the late morning
hours due to dense sea fog, so please check for TAF updates and
amendments. Fog may redevelop at the terminals during the
overnight hours tonight, mainly after midnight.

&&

.Marine...
Dense Sea Fog continues over the near shore waters adjacent to
southeast Georgia during the predawn hours. Sea fog may expand
into the near shore waters adjacent to northeast Florida early
this morning, mainly for the waters north of St. Augustine. Sea
fog may linger into tonight over these waters. Otherwise, high
pressure will remain positioned to the northeast of our waters
today, with our local pressure gradient remaining weak enough to
result in sea breeze development over the near shore waters this
afternoon. Meanwhile, a cold front will enter the southeastern
states tonight, resulting in offshore winds developing that will
persist through Wednesday night. This boundary will move close to
the southeast Georgia waters on Thursday, but should stall just to
the north of our region. A stronger series of cold fronts will
approach our area from the west this weekend, with offshore winds
expected to strengthen somewhat beginning on Friday. However, wind
speeds and seas should remain below caution criteria through at
least Saturday night.

Rip Currents: A lingering long period easterly ocean swell will
keep a moderate risk in place at the northeast Florida beaches
today. A low risk is anticipated for the rest of the week.

&&

.Climate...

Record Highs for today
JAX 84/1943...GNV 87/1943...AMG 79/1949...SSI 77/1974

Record highs for January 18th
JAX 83/1937...GNV 85/1937...AMG 79/1952...SSI 77/1952

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  79  56  76  57 /   0  10  10  10
SSI  75  55  74  58 /  10   0  10   0
JAX  80  56  78  57 /  10   0  10  10
SGJ  77  58  76  58 /  10   0   0  10
GNV  79  53  78  56 /   0   0   0  10
OCF  79  55  79  57 /   0   0   0  10

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Dense Fog Advisory until 9 AM EST this morning for Baker-Coastal
     Duval-Coastal Nassau-Inland Duval-Inland Nassau.

GA...Dense Fog Advisory until 9 AM EST this morning for Appling-Bacon-
     Brantley-Charlton-Coastal Camden-Coastal Glynn-Inland
     Camden-Inland Glynn-Pierce-Ware-Wayne.

AM...Dense Fog Advisory until 9 AM EST this morning for Coastal
     waters from Altamaha Sound to Fernandina Beach FL out 20 NM.

&&

$$

Nelson/Enyedi/Elsenheimer



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