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000
FXUS62 KJAX 111510
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
1010 AM EST Mon Dec 11 2023

...New UPDATE...

.UPDATE...
Issued at 1008 AM EST Mon Dec 11 2023

For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf

Not much change in the forecast today as broad high pressure
around 1026 mb located over the lower MS valley to central TN
works slowly into the area, but will be shift up into the Appalachians
tonight. While winds will decrease early today to 10-15 mph, the
temps will be chilly as cool advection continues. Have shaved off
a couple of degrees from the max temps today based on latest guidance
and model thickness fields. Should end up about 7-10 deg below
normal but will have full sun.

For the marine forecast, have let parts of small craft advy
expire. Latest observations, as well as GOES derived low level
wind show 15-25 kt over waters, but taking about 80 percent of
the GOES values, shows we have winds near 20 kt offshore. So SCA
offshore waters still looks very reasonable, with seas up to 5-7
ft, highest near the outside waters near the Gulf Stream.
Probably will be able to let the next SCA (AMZ472, 474) expire
about 3 PM.

&&

.SYNOPSIS...
Issued at 352 AM EST Mon Dec 11 2023

Overnight surface analysis depicts a strong cold front racing
eastward off of FL`s Atlantic coast and Keys, with strengthening
low pressure (999 millibars) situated along this front over the
Mid-Atlantic region that was accelerating northward towards
coastal New England. Meanwhile, high pressure (1026 millibars) was
centered over the western Gulf of Mexico in the wake of this
front, with this surface ridge quickly building into the
southeastern states. Aloft...troughing along the U.S. eastern
seaboard was taking on a negative tilt, while a reinforcing
shortwave trough was diving east-southeastward across the Upper
Midwest and the Mid-Mississippi Valley. Following an impressive
wind event during the cold frontal passage on Sunday evening
across portions of our region, northwesterly winds have subsided
but remain breezy. The back edge of lower stratus and
stratocumulus cloudiness has cleared inland southeast GA and
western portions of the Suwannee Valley as of 09Z, where
temperatures were plunging through the low to mid 40s.
Temperatures were falling to around 50 degrees along the northeast
FL coast. Dewpoints ranged from the mid 30s along the Ocmulgee and
upper portions of the Altamaha Rivers to the mid and upper 40s
along the northeast FL coast.

&&

.NEAR TERM...
(Today and Tonight)
Issued at 352 AM EST Mon Dec 11 2023

Low stratus and stratocumulus cloudiness, driven by strong cold
air advection, will push offshore of our Atlantic coast well
before sunrise. High pressure building along the northern Gulf
coast and the southeastern states will migrate northeastward
today, reaching a position over the southern Appalachians tonight.
Despite sunny skies today, cold air advection will keep highs in
the mid to upper 50s for locations along and north of the
Interstate 10 corridor as well as coastal locations, with highs
climbing to the lower 60s this afternoon for inland locations
south of Gainesville. Gusty northwesterly winds this morning will
subside towards noon as our local pressure gradient loosens.

A reinforcing shortwave trough that will be diving east-
southeastward from the Mid-Mississippi Valley through the
Tennessee Valley and the Carolinas tonight will be accompanied by a
110-knot jet streak at 250 millibars (around 35,000 feet). This
jet streak, positioned well north of our region, will begin to
advect thin cirrus into our area from south to north overnight.
Winds at inland locations will quickly decouple around sunset,
setting the stage for radiational cooling overnight. A light
northerly breeze will likely continue overnight at coastal
locations as high pressure begins to strengthen over the
Appalachians and wedges down the southeastern seaboard. This
weather pattern will result in a large temperature gradient across
our region by early Tuesday morning, with lows falling to near
freezing across inland southeast GA, the Suwannee Valley, and for
locations along the I-10 corridor to the west of downtown
Jacksonville. A Frost Advisory has been issued for these locations
overnight through early Tuesday morning, and a light freeze cannot
be ruled out for locations northwest of Waycross and Jesup.
Lows will remain in the low to mid 40s overnight for locations
along and east of the I-95 corridor, with coastal temperatures
possibly rising towards sunrise as our local pressure gradient
begins to tighten.

&&

.SHORT TERM...
(Tuesday through Thursday)
Issued at 352 AM EST Mon Dec 11 2023

Strengthening high pressure will be centered just to the north
Tuesday, beginning what will be a prolonged period with elevated
onshore flow. While high pressure will be centered a little
further to the north by Thursday, the high will be even stronger.
In addition, inverted troughing over the coastal waters will help
to pinch the pressure gradient along the coast, leading to gustier
winds, especially at the coast. Wind gusts of 30 to 40 mph will
be common along the coast by Thursday.

This will be a mainly dry period, but increasing moisture and
convergence due to coastal trough could lead to a few coastal
showers later in this period. And the moist onshore flow will also
keep the region mainly cloudy during the period.

High temperatures will trend a little below normal this period,
due to combination of cloud coverage and onshore flow across
relatively cooler coastal waters. A broad range in temperatures is
expected for the night times due to northeast flow across the
waters. Lows Tuesday night lows will range from the upper 30s
inland SE GA, to the mid 50s along the NE FL coast. For Wednesday
night lows will range from mid 40s inland SE GA, to around 60
along the NE FL coast.

&&

.LONG TERM...
(Thursday Night through Sunday)
Issued at 352 AM EST Mon Dec 11 2023

Strong high pressure will remain to the north through at least
Friday. This will continue the elevated onshore flow, especially at
area beaches.

Long range models are inconsistent with how fast moisture returns
from the south, but the chance for showers increases through the
weekend.

With continued onshore flow, cloud coverage and increasing precipitation
chances temperatures will trend a little below normal during the
day, but near to above at night.

&&

.AVIATION...
(12Z TAFS)
Issued at 547 AM EST Mon Dec 11 2023

Lingering MVFR ceilings at CRG and SGJ will exit before 12Z, with
VFR conditions then prevailing at the regional terminals.
Northwesterly surface winds sustained at 10-15 knots will continue
through around 20Z, followed by winds shifting to northerly and
diminishing to around 10 knots. Northerly winds will continue to
subside to less than 5 knots at the inland terminals towards 23Z,
with northerly winds remaining sustained around 5 knots at the
SSI and SGJ coastal terminals. Winds will shift to north-
northwesterly at the coastal terminals during the predawn hours on
Tuesday, with speeds increasing to 5-10 knots towards sunrise.
Mostly thin cirrus cloudiness will increase from south to north
during the overnight and predawn hours on Tuesday.

&&

.MARINE...
Issued at 352 AM EST Mon Dec 11 2023

High pressure building into the southeastern states in the wake of
the overnight cold frontal passage will keep Small Craft Advisory
level wind speeds throughout our local waters through the mid-
morning hours, with Small Craft Advisory conditions continuing
into the late afternoon hours for the offshore waters adjacent to
northeast Florida. Speeds should drop below Small Craft Advisory
levels for the near shore waters and the offshore waters adjacent
to southeast GA before noon. Seas of 3-5 feet are expected today
for the near shore waters, with seas of 5-7 feet offshore that
will subside to 4-5 feet this afternoon for the offshore waters
adjacent to southeast GA.

Winds and seas will briefly subside overnight as high pressure
migrates northeastward to a position over the southern
Appalachians. Seas will subside to the 2-4 foot range near shore
this evening, with 3-5 foot seas forecast offshore. This high
pressure center will then strengthen as it becomes anchored over
the Carolinas on Tuesday, resulting in strengthening northeasterly
winds and building seas throughout our local waters. Winds and
seas will increase back to Small Craft Advisory levels offshore by
Wednesday, with occasional Gale Force wind gusts beginning on
Wednesday night. Small Craft Advisory conditions will begin for
the near shore waters on Wednesday evening.

An extended period of strong onshore winds and building seas is
expected into the upcoming weekend as strong high pressure remains
situated to the north of our waters and low pressure gradually
takes shape over the eastern Gulf of Mexico. A coastal trough
developing over our near shore waters will also generate
occasional showers beginning on Wednesday. Seas near shore will
build to the 7-10 foot range for the near shore waters by
Thursday, with offshore seas likely building above 10 feet by
Thursday night.

Rip Currents: Strong offshore winds through around noon should
result in a low rip current risk at all area beaches today. Winds
will become onshore by Tuesday morning, with gradually
strengthening speeds and building seas resulting in a moderate rip
current risk at all area beaches on Tuesday. A high risk of
dangerous rip currents is expected from Wednesday through the
upcoming weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  56  32  60  38 /   0   0   0   0
SSI  58  43  62  49 /   0   0   0   0
JAX  59  37  64  49 /   0   0   0   0
SGJ  59  46  68  57 /   0   0   0  10
GNV  60  37  67  49 /   0   0   0   0
OCF  61  38  68  52 /   0   0   0   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Frost Advisory from 2 AM to 8 AM EST Tuesday for FLZ020-021-023-
     024-030-035-122-222.

GA...Frost Advisory from 2 AM to 8 AM EST Tuesday for GAZ132>136-149-
     151>153-162-163-165-250-264-350-364.

AM...Small Craft Advisory until 3 PM EST this afternoon for AMZ472-
     474.

&&

$$