753
FXUS62 KJAX 161741
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
141 PM EDT Mon Sep 16 2024

...New AVIATION...

.UPDATE...
Issued at 939 AM EDT Mon Sep 16 2024

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

Precipitable water values across northeast FL is between 1.85 to
1.95 inches with drier air indicated just north of the Altamaha
around 1.65 inches. "Drier" air have started working into the
northern part of the CWA with north-northeasterly surface winds
across the area and will continue to do so today. Wrap around
cloudiness will remain in place across the region as PTC -
Potential Tropical Cyclone offshore of South Carolina moves to the
northwest into South Carolina this afternoon as unorganized low.
Limited precipitation potential this afternoon across the region
with isolated to widely scattered showers south of Waycross. There
will some convection closer to north central FL and Flagler
counties this afternoon with some convergent feature noted in the
models in addition to the higher moisture levels.

Long period onshore flow and astronomical high tides will
continue to promote poor to hazardous marine and beach conditions
through tonight, then improving conditions Tuesday.

&&

.SYNOPSIS...
Issued at 448 AM EDT Mon Sep 16 2024

Early morning surface analysis depicts the center of Potential
Tropical Cyclone (PTC) #8 drifting over the Gulf Stream Waters
adjacent to the South Carolina coast. Meanwhile, strong high
pressure (1028 millibars) remains anchored off coastal New
England, with this feature wedging down the spine of the
Appalachian mountains and into the Deep South. Otherwise, a
stubborn, wavy and nearly stationary frontal boundary remains in
place along the Interstate 4 corridor in central FL, with this
boundary extending along the northern Gulf coast. Aloft...the "Rex
Blocking" pattern continues over the eastern half of the nation,
with stout ridging extending across the eastern Great Lakes, New
England, and the Mid-Atlantic states. This feature was keeping the
remnant trough that was once Francine drifting over the Ozarks
and lower Mississippi Valley, with this trough axis extending
southeastward along the northern Gulf coast. Low-topped showers
and lower stratus clouds continue to advect southwestward from
PTC #8 across our Atlantic waters, with this activity brushing the
I-95 corridor. Multi-layered cloudiness prevails across our area,
but thinner, mainly high altitude cloudiness was located over
inland portions of southeast GA, where dewpoints were falling
through the 60s as of 08Z and temperatures were generally around
70. Breezy northerly winds prevail at coastal locations, with
temperatures and dewpoints in the 70s elsewhere.

&&

.NEAR TERM...
(Today and Tonight)
Issued at 448 AM EDT Mon Sep 16 2024

PTC #8 should organize into a Tropical Storm (Helene) later this
morning as it drifts northwestward towards the Carolina coast,
with landfall expected by late afternoon. Wrap-around moisture on
the southwestern periphery of this cyclone`s circulation will keep
stubborn low and mid level cloudiness in place across most of
coastal southeast GA, northeast and north central FL into the
early afternoon hours, with a few low topped showers and/or
drizzle occasionally impacting locations along the I-95 corridor
this morning. Breaks in the multi-layered cloudiness should
develop this afternoon across north central FL, where slightly
deeper moisture, a destabilizing atmosphere, and the presence of
the stubborn frontal boundary over central FL could develop
showers and a few embedded thunderstorms by late afternoon as
highs climb to the mid and upper 80s. Cloudiness will also thin
out by the mid to late afternoon hours elsewhere, with low level
winds backing to northwesterly, ushering in a drier air mass that
will allow highs to climb to the low and mid 80s for most
locations by late afternoon. This drier air mass should shut off
showers rotating around the periphery of PTC #8 later this
afternoon along the I-95 corridor.

Any convection that manages to develop across north central FL
late this afternoon should diminish by sunset this evening. PTC #8
will continue its slow northwestward motion across inland portions
of South Carolina tonight, with a drier air mass overspreading our
region overnight. Fair skies and diminishing winds will allow for
radiational cooling for locations along and north of the I-10
corridor, allowing lows to fall below mid-September climatology,
as values bottom out in the mid 60s for most of inland southeast
GA by sunrise on Tuesday. Lows for inland northeast FL will fall
to the upper 60s, with lower 70s closer to the lingering front in
north central FL, and low to mid 70s for coastal locations.

&&

.SHORT TERM...
(Tuesday through Wednesday
Issued at 448 AM EDT Mon Sep 16 2024

The area will be on the southern periphery of a weakening,
stacked low associated with the remnants of PTC #8 over the
Carolinas through mid-week. West-southwesterly flow will advect
in drier air on the south side of the low limiting convection over
much of SE GA. Convection will return to be diurnally driven and
enhanced by the sea breezes. In the WSW flow, the Atlantic sea
breeze will be pinned to the I-95 corridor. Isolated to scattered
showers and storms will be possible each afternoon into evening
mainly over NE FL. Temperatures warm to above climo with highs in
the mid 80s to low 90s and lows in the upper 60s to low 70s.

&&

.LONG TERM...
(Thursday through Sunday)
Issued at 448 AM EDT Mon Sep 16 2024

The upper low lifts northeastward into the mid-Atlantic region
through Friday as surface high pressure builds down into the SE
from the Great Lakes region. NNW flow aloft develops which will
maintain drier conditions across the area. Isolated to widely
scattered showers and storms will be possible with the best
chances in the NE FL. The upper low dives south down the eastern
seaboard for the weekend as surface high pressure wedge extends
down the eastern US. This will bring a return of breezy
northeasterly winds for the weekend and potentially higher chances
for rain. Above normal temps on Thursday and Friday return to
below normal for the weekend with the potential increase of cloud
cover and rain.

&&

.AVIATION...
(18Z TAFS)
Issued at 135 PM EDT Mon Sep 16 2024

Last gasp of MVFR CIGS at local TAF sites will slowly erode or
lift with diurnal heating this afternoon, with all sites becoming
MVFR by sunset with GNV/SGJ the last of the locations to become
VFR this evening. Rainfall chances are on the low side so have
only included VCSH at GNV/SGJ with this package until 00Z. Some
clearing of skies and cooling of the boundary layer tonight along
with near calm winds developing will lead to patchy fog formation
and low stratus development at inland TAF sites with LIFR CIGS
expected at GNV/VQQ in the 09-13Z time frame, while probs not as
high at the coastal TAF sites, so have only added some MVFR conds
at JAX and left SGJ/SSI/CRG at VFR levels. During diurnal heating
Tuesday morning some redevelopment of MVFR CIGS is possible but
for now have left as SCT020 for now in the 13-18Z time frame but
TEMPO MVFR CIGS in the 1500-2500 ft range may need to be added in
later TAF packages.

&&

.MARINE...
Issued at 448 AM EDT Mon Sep 16 2024

Potential Tropical Cyclone 8 will likely become a Tropical Storm
later this morning before pushing northwestward towards coastal
South Carolina this afternoon. Seas will peak this morning in the
7-9 foot range offshore and 6-8 feet near shore. Small Craft
Advisory conditions will continue throughout our local waters this
morning, with conditions improving over the near shore waters by
this evening as winds shift to northwesterly and diminish. Seas
should remain at Caution levels of 4-6 feet near shore tonight,
with 5-7 foot seas prevailing offshore. Seas will then fall below
Small Craft Advisory criteria offshore by early Tuesday morning,
with Caution level seas prevailing through Tuesday afternoon.

A leftover frontal boundary stretching across central Florida
will slowly lift northward across the northeast Florida waters
through midweek, possibly developing a few showers and
thunderstorms during the late afternoon and early evening
hours. Seas will diminish to the 2-4 foot range both near shore
and offshore by midweek. Another surge of onshore winds will be
possible towards the weekend as strong high pressure wedges down
the southeastern seaboard.

Rip Currents/High Surf: Breaker heights will peak around 6 feet
this morning at the northeast FL beaches and 4-5 feet at the
southeast GA beaches. Surf heights will begin to gradually
diminish this afternoon as winds shift to northwesterly, but a
high risk of rip currents will continue at all area beaches today.
Breaker heights will remain elevated in the 3-5 foot range on
Tuesday at the northeast FL beaches and 2-3 feet at the southeast
GA beaches, with a lingering northeasterly swell likely creating a
higher end moderate risk at area beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  83  64  85  68 /  20   0  20  10
SSI  83  74  83  73 /  20   0  10  10
JAX  84  68  87  72 /  20  10  30  20
SGJ  84  74  87  74 /  30  10  30  20
GNV  85  68  89  71 /  20   0  30  10
OCF  87  70  90  72 /  30  10  30  10

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 5 AM EDT Wednesday for FLZ033-038-
     132-137-325.

     Coastal Flood Advisory until 5 AM EDT Tuesday for FLZ124-125-133-
     138.

     High Rip Current Risk through late tonight for FLZ124-125-133-
     138.

GA...Coastal Flood Advisory until 5 AM EDT Tuesday for GAZ154-166.

     High Rip Current Risk through late tonight for GAZ154-166.

AM...Small Craft Advisory until 5 PM EDT this afternoon for AMZ450.

     Small Craft Advisory until 11 PM EDT this evening for AMZ452-454.

     Small Craft Advisory until 5 AM EDT Tuesday for AMZ470-472-474.

&&

$$