Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 160158

Area Forecast Discussion
National Weather Service Jacksonville FL
858 PM EST Sun Dec 15 2019


Sfc high pressure is off the southeast U.S. coast and will continue
pushing eastward through early this week. A warming regime is
slowly getting underway as winds at the sfc have come around to the
east and just above the sfc winds are east and becoming southeast
to south by 12z Monday. Lows tonight as not cold as last night
but 40s to lower 50s anticipated, warmest readings near the coast
due to a light east to southeast wind. Tweaked min temps down
based on trends. Warming regime especially noted Monday with
highs in the upper 70s to near 80. Main challenge again is fog
forecast for tonight and continued to show patchy to areas of fog
for later tonight, with some locally dense fog likely for locations
inland from the coast. Best fog potential appears to be from
around I-95 westward to Highway 84 in southeast GA and to near
I-75 in northeast FL.

Southeast winds near 10 kt expected rest of tonight with seas
around 2-4 ft mainly from east swells at 8 to 10 seconds. No
significant changes to the forecast are needed.



.NEAR TERM [Through Tonight]...

Seasonally cool, clear skies and another round of fog as surface
high pressure centered over the local area builds offshore
through tonight. Low level winds will go calm inland tonight while
near the coast and over the coastal waters winds will veer more
SE as the ridge center builds offshore. This transition will
moderate temperatures and increase low level moisture with lows
expected to be about 5-10 deg warmer tonight compared to last
night. After midnight, conditions are favorable for shallow ground
fog to develop inland once again with the focus area first
developing near the I-95 corridor and spreading inland and to the
NNW across inland SE GA through sunrise where patchy dense fog was

.SHORT TERM [Monday Through Tuesday Night]...

Warm southerly flow develops Monday with a rebound in temperatures
above normal values rising into the mid to upper 70s inland as the
surface high shifts farther offshore of the SE Atlantic coast.
Aloft, upper level flow backs SW with increasing high cirrus from
the west Monday afternoon into Monday night. Dry conditions will
prevail until Tuesday as the next frontal system approaches from
the west. Dynamical forcing across the local area will be much
weaker compared to the last system as the parent surface low
tracks well to the north and the strongest dynamics aloft lag the
deepest moisture and low level lift near the cold front. There is
a low potential for isolated t`storms Tue afternoon and Tue
evening with meager low level instability 500-1000 J/kg focused
across our southern FL zones south of GNV to SGJ per the GFS where
0-6 km bulk shear near 40 kts by 00z. Cold front clears SE GA Tue
afternoon and settles across NE FL Tue night with lingering clouds
through Tue night. Above climo temps continue into Tue ahead of
the front with some locations across NE FL nearing record highs in
the lower 80s. Temps cool into the 40s for most areas Tue night
trailing frontal passage.

.LONG TERM [Wednesday Through Sunday]...

WED & THU...Dry with below normal temperatures with an inland
freeze expected Wed night. Post-frontal clouds will gradually
decrease Wed as mid/upper level troughs press downstream of the
area. At the surface, high pressure across south TX will extend a
ridge axis eastward across the Gulf Coast states. This regime will
bring a dry and chilly low level NNW flow which highs only in the
50s across most areas Wed with and inland freeze for SE GA and
west of the Highway 301 corridor Wed night. The pressure gradient
will remain elevated Wed night to continue winds near 5 mph inland
to near 10 mph toward the Atlantic coast which will create wind
chills in the 20s for many areas around sunrise Thu morning. The
surface ridge builds north of the region Thu which will veer low
level winds more ENE into Thu evening. This pattern transition
will bring a gradual warming trend with highs warming into the
mid/upper 50s for SE GA Thu and highs in the low/mid 60s across NE
FL. Thu night low temps will also moderate into the mid/upper 30s
across inland SE GA to the 40s/low 50s across NE FL, with frost
not overly likely at this time across SE GA given influx of high
cirrus clouds from the west through the night.

FRI THROUGH SUN...Increasing rain chances Fri-Sat with locally
heavy rainfall potential and warming trend in temperatures toward
near normal values. A coastal trough forms along the local coast
Fri bringing a chance of coastal showers. Fri night a surface low
forms along the inverted coastal trough offshore of the coast as a
strong upper level trough and associated surface cold front press
steadily east across the Gulf Coast states. Best chance of
rainfall Fri night into Sat will focus along the local Atlantic
coast where coastal convergence around the low offshore and
increased forcing aloft could create localized heavy rainfall.
Model discrepancies between GFS/ECMWF regarding upper level low
structure and progression Sat into Sun with the 00Z ECMWF showing
a weaker but progressive system while the GFS develops a strong,
deepening low across the SE region and continues elevated rain
chances into Sun with the upper level low passage. At this trended
toward decreasing rain chances Sat night into Sun. Guidance is in
good agreement at this time keeping the local area in the `cool`
section of this system so refrained from inclusion of tstorms at
this time, however, if GFS solution of potent upper level low pans
out, elevated instability will bring at least an isolated tstorm
change. Cooler and drier NNW flow develops Sunday as storm system
progresses downstream with temperatures cooling to near to below
climo values.

[Through 00Z Tuesday]

VFR through this evening but like last night, there is fog
potential. But unlike last night, there may equal chances of fog
and stratus, since winds just above the sfc will be higher and
produce a bit more turbulent mixing. Indicated fog developing at
VQQ by around midnight and other TAFs by 08z-11z and continued to
to show low flight conditions for JAX, VQQ, SSI, and GNV.
Uncertain on fog potential for SGJ and CRG where guidance and
cross-over temps not as big. Shortly after 14z, anticipate VFR
rest of the day with southerly winds increasing to near 10 kt with
a few higher gusts in the aftn.


High pressure over the local waters will shift farther east
Monday as south winds develop. Seas and winds increase late Monday
into Tuesday ahead of an approaching cold front to exercise caution
levels over the outer waters. The front will press south of the
waters late Tuesday with isolated thunderstorm potential. Strong
north winds Wednesday will bring Small Craft Advisory conditions
to at least the outer waters as surface high pressure builds
across the Gulf Coast States. The high builds north of the waters
Thursday and Friday with a gradual decrease in winds and seas as
onshore flow develops with marginal advisory conditions over the
outer waters.

Rip Currents: Low risk today & Monday.



AMG  44  76  60  75  40 /   0   0  20  70  40
SSI  53  72  61  75  45 /   0   0  10  30  40
JAX  49  78  60  79  45 /   0   0  10  30  50
SGJ  55  78  63  79  47 /   0   0  10  30  40
GNV  49  79  61  79  45 /   0   0  10  30  40
OCF  51  80  61  80  47 /   0   0  10  30  40


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