386
FXUS62 KJAX 161841
AFDJAX

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

...New NEAR TERM, SHORT TERM, LONG TERM, MARINE, HYDROLOGY...

.NEAR TERM...
(Through Tonight)
Issued at 227 PM 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

This afternoon...While drier air aloft and at the surface slowly
seeps southward into SE GA, there still will be a few isolated
showers from the I-10 corridor northward into Coastal SE GA, while
diurnal heating into the mid/upper 80s across NE FL and lingering
deep moisture will still allow for scattered showers and isolated
storms to develop across NE FL, mainly along and south of a line
from Gainesville to St. Augustine, with the best chances of an
isolated storm with heavy downpours across Marion/Putnam/Flagler
counties into the early evening hours.

Tonight...After a few early evening showers/isolated storms across
Flagler/Putnam/Marion counties, expect a general decrease in
cloudiness as a slightly drier West to Northwest steering flow on
the SW side of PTC Eight brings mostly clear skies to most of SE
GA with some lingering high clouds across most of NE FL through
the night. This overall slight pattern shift will lead to the
first rain-free overnight forecast along with some of the coolest
temps so far this month with lower/middle 60s across inland SE GA,
middle/upper 60s over most of inland NE FL and lower 70s along the
Atlantic Coastal areas. Winds becoming Northwest and weakening to
less than 5 mph over inland areas by the overnight hours will
likely allow for some patchy fog formation towards sunrise.

&&

.SHORT TERM...
(Tuesday through Wednesday night)
Issued at 227 PM EDT Mon Sep 16 2024

This period will be mainly dominated by the presence of a stacked
upper low just north of the region and associated trough, mostly
associated with the remnants of Potential Tropical Cyclone Eight.
Flow will be generally west to southwest around the base of the
trough, which will also keep the sea breeze pinned to the coast.
With the diffuse frontal boundary pushed generally south of the
area and some drier air aloft advected into the area at times,
chances for convection will be toned down across most of the area,
especially on Tuesday. Chances for convection will become more
diurnal and daytime heating influenced compared to the recent
stubborn pattern. Best chances for isolated to widely scattered
showers/t`storms during the period will be south of I-10 and near
the coastline where the pinned sea breeze develops. This regime
will also allow temps to rise closer to if not slightly above
average, with mid to upper 80s Tuesday and upper 80s to near 90
more common by Wednesday.

&&

.LONG TERM...
(Thursday through next Monday)
Issued at 227 PM EDT Mon Sep 16 2024

The upper troughing pattern will not change significantly for at
least the start of the long term period, as the parent upper low
lifts northeastward and troughing across the area elongates. This
should keep a pretty similar pattern for Thursday into Friday,
with the main difference being a gradual veering of flow towards
the northwest to possibly even northward. This type of flow regime
would generally favor lower than normal shower/t`storm chances,
and likely confined closer to the coasts and the influence of the
sea breeze.

Guidance starts to diverge towards the upcoming weekend, though
the general consensus looks to be for the aforementioned upper low
to start to dive back southward along the eastern seaboard and/or
western north Atlantic. This will return a breezy northeasterly
pattern to the area as surface ridging builds into the
southeastern states in response. The extent of our rain potential
will highly depend on the proximity the upper low gets to our
region and/or how far south the associated digs, though for now
looking like more eastern areas and especially the coasts have the
highest chances, especially with the potential for development of
a coastal trough with the proximity of the upper low.

Temperatures start near to slightly above average for the end of
the work week, then trend downward towards near to below average
for the weekend.

&&

.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 227 PM EDT Mon Sep 16 2024

Small Craft Advisory conditions in the gusty North-Northeast flow
at 15-20 knots this afternoon will shift to the Northwest tonight
and slowly diminish as PTC Eight tracks further inland over the
Carolinas which will slowly bring an end to Small Craft Advisory
headlines as winds drop below 20 knots this evening and seas
slowly fall being 7 feet later tonight or Tuesday morning. In the
wake of PTC Eight lifting NW into the Carolinas a weak pressure
pattern will remain in place through the mid-week time frame with
light Southwest flow and diurnal sea breeze pattern over the near
shore waters. Late in the week a frontal passage is expected on
Thursday, then high pressure building into the Carolinas Friday
and Saturday, which will lead to the next increase in Northeast
flow likely close to Small Craft Advisory levels in the upcoming
weekend time frame.

Rip Currents: High risk of rip currents and rough surf of 4-6 ft
today will likely become Moderate to marginally High on Tuesday as
offshore flow sets up, but lingering swells will keep
surf/breakers in the 3-5 ft range.

&&

.HYDROLOGY...
Issued at 227 PM EDT Mon Sep 16 2024

The St. Johns River Basin from Jacksonville southward through
Putnam County has started to reach Moderate Flood levels during
the latest high tide cycle, so have upgraded the Coastal Flood
Advisory to a Coastal Flood Warning with the upcoming full moon
over the next couple of days along with all of the runoff from all
of the recent heavy rainfall. Peak tidal levels will generally be
in the 2.0 to 2.5 ft above MHHW along the St. Johns River Basin.
Along the SE GA/NE FL beachfront locations, similar peak tidal
levels in the 2.0 to 2.5 ft above MHHW are expected early this
week, which should remain in the Minor Flood categories, so have
continued the Coastal Flood Advisory in these areas, although the
current rough surf/breakers of 4-6 ft today will likely continue
minor beach erosion during times of high tide at local beaches as
well.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  62  84  67  87 /  10  10  10  20
SSI  68  84  73  86 /  10  10  10  30
JAX  67  87  71  89 /  10  20  20  50
SGJ  71  87  73  89 /  10  20  20  40
GNV  68  88  70  89 /  10  30  10  50
OCF  70  90  71  91 /  20  30   0  40

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Warning until 5 AM EDT Wednesday for FLZ033-038-
     125-132-137-225-325.

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

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

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

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

AM...Small Craft Advisory until 6 PM EDT this evening for AMZ450.

     Small Craft Advisory until midnight EDT tonight for AMZ452-454.

     Small Craft Advisory until 6 AM EDT Tuesday for AMZ470-472-474.

&&

$$