681
FXUS62 KJAX 181051
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
651 AM EDT Fri Oct 18 2024

...WINDY CONDITIONS CONTINUE AT COASTAL LOCATIONS...
...HIGH RISK OF DEADLY RIP CURRENTS AT ALL AREA BEACHES...
...MODERATE TIDAL FLOODING CONTINUES FOR SOUTHERN PORTIONS OF THE
ST. JOHNS RIVER BASIN...

...New AVIATION...

.SYNOPSIS...
Issued at 301 AM EDT Fri Oct 18 2024

Early morning surface analysis depicts strong high pressure (1031
millibars) centered over the Ohio Valley, the Appalachians, and
the eastern Great Lakes. This sprawling high pressure center
continues to wedge down the southeastern seaboard, with weak
coastal troughing now situated over the near shore waters adjacent
to northeast FL. Aloft...troughing along the U.S. eastern
seaboard was lifting northeastward, allowing for deep ridging that
extends from the lower Mississippi Valley northward through the
Great Lakes region to build eastward. Latest GOES-East derived
Total Precipitable Water imagery indicates that a very dry air
mass persists for locations along and north of the Interstate 10
corridor, where PWATS were less than a half inch, while values for
locations south of I-10 still remain less than one inch.
Dewpoints within the very dry air mass ranged from the upper 30s
to lower 40s as of 08Z across inland southeast GA and northern
portions of the Suwannee Valley, where radiational cooling has
allowed temperatures to fall through the 40s overnight. Meanwhile,
coastal troughing and convergent low level onshore flow has
driven marine stratocumulus onshore along the coastal counties,
with a larger patch of more opaque stratocumulus streaming across
the I-4 corridor in central FL expanding across north central FL.
Temperatures across the rest of northeast and north central FL
ranged from the 50s at inland locations to the mid 60s at coastal
locations, where a steady northeast breeze prevails. Dewpoints
across most of northeast and north central FL generally ranged
from the mid 40s to the mid 50s.

&&

.NEAR TERM...
(through Tonight)
Issued at 301 AM EDT Fri Oct 18 2024

High pressure will continue to slowly strengthen near the eastern
Great Lakes region today, while coastal troughing gradually
sharpens over the near shore waters adjacent to northeast FL. This
sprawling high pressure center will continue to wedge down the
southeastern seaboard, serving to tighten our local pressure
gradient even further this afternoon. Breezy onshore winds at
coastal locations this morning will become windy this afternoon,
as northeasterly winds increase to 20-25 mph with occasional
gusts around 35 mph expected at the northeast FL coast by late
this afternoon. Marine stratocumulus will continue to overspread
our region this morning and will then tend to shift southward and
away from southeast GA this evening. The sharpening coastal trough
and convergent low level onshore winds will develop a few light
showers over the Atlantic waters adjacent to northeast FL this
afternoon, with isolated to widely scattered mainly light showers
or sprinkles possible by late afternoon and evening for locations
from around Ponte Vedra southward, with a few of these showers
moving inland across the St. Johns River basin and across U.S.
Highway 17 in Putnam and Clay Counties towards sunset. Otherwise,
ridging aloft will gradually build into our region from the
northwest, with rising heights aloft offsetting the marine
stratocumulus cloud cover, allowing highs to climb into the 70s
area-wide this afternoon.

Fair skies will prevail across southeast GA tonight as high
pressure continues to wedge into the southeastern states. A tight
local pressure gradient will likely not allow for radiational
cooling, although clear skies will result in lows falling to the
mid and upper 40s for interior southeast GA, while an onshore
breeze keeps coastal lows in southeast GA in the upper 50s to
around 60. Marine stratocumulus will persist across most of
northeast and north central FL overnight, with low level
convergence weakening somewhat after midnight. Evening showers
moving onshore should dissipate as this low level convergence
weakens, and a tight local pressure gradient will keep breezy
conditions going overnight at coastal locations, where lows will
remain in the 60s. Inland lows will drop to the mid and upper 50s,
except around 60 for north central FL.

&&

.SHORT TERM...
(Saturday through Sunday night)
Issued at 301 AM EDT Fri Oct 18 2024

Not much change in the pattern is expected throughout the weekend
as surface high pressure remains nearly stationary north of the
area near the Ohio River Valley. This will also continue a brisk
onshore northeast flow, and gradually increase low level moisture
back into much of the region, especially for northeast FL. A few
isolated showers will be possible near the northeast FL coastline
as well as for many areas generally south of I-10 throughout the
weekend accordingly, though remaining dry for the "northern half"
of the CWA into southeast GA with a fairly sharp cut off in layer
moisture, precip chance, and cloud cover from southeast to
northwest. Temperatures continue to gradually moderate, closer to
normal with generally mid to upper 70s and perhaps a few values in
the low 80s furthest south. Milder than the past few nights with
lows in the 50s north an west and 60s south and east and the
coast.

The onshore flow combined with us coming out of the full
"supermoon" from this week will likely persist some tidal flooding
concerns along the northeast FL Atlantic Coast and St. Johns River
through at least Saturday, and possibly into Sunday as well. Rip
current risk is also expected to remain high at all area beaches
throughout the weekend as this similar regime continues.

&&

.LONG TERM...
(Monday through Thursday)
Issued at 301 AM EDT Fri Oct 18 2024

Onshore flow regime continues through at least the start of the
long term period, though looks to weaken during the start of the
next work week as high pressure starts to shift more
northeastward into the North Atlantic. Chances for isolated
showers will remain a possibility during most of the long term
over interior northeast FL and especially towards the coast.
Although modest differences in timing and magnitude, guidance is
in agreement that another frontal boundary will approach the
region by around the Thursday time frame. Temperatures continue
the same trend from the short term period, towards near to
slightly above average.

&&

.AVIATION...
(12Z TAFS)
Issued at 650 AM EDT Fri Oct 18 2024

VFR conditions are expected for the forecast period. Ceilings
hover around 3,500-4,000 feet as stratocumulus move onshore. Some
precipitation could develop around SGJ after 18z as onshore winds
bring a little more moisture to the area. Winds will be out of the
north to northeast and increase in speed into the afternoon
reaching 10-15 kts with gusts of 20 to 25 kts. Winds will begin to
taper off around 06z at most sites but looks to stay breezy at
SGJ.

&&

.MARINE...
Issued at 301 AM EDT Fri Oct 18 2024

Strong high pressure centered over the Ohio Valley and the eastern
Great Lakes will continue to wedge down the southeastern seaboard,
creating strong northeasterly winds through the weekend and early
portions of next week. Meanwhile, coastal troughing taking shape
over the near shore waters adjacent to northeast Florida will
generate occasional showers beginning this afternoon and
continuing through early next week. Small Craft Advisory
conditions will remain ongoing for the offshore waters adjacent
to northeast FL, where seas of 5-7 feet today will build to 6-8
feet this weekend. A surge in wind speeds late this afternoon and
evening will bring Small Craft Advisory conditions to the near
shore waters as well as the offshore waters adjacent to southeast
GA. Seas are expected to build to Small Craft Advisory levels near
shore beginning on Saturday night, with elevated winds and seas
expected near shore through Monday. High pressure will then weaken
as it settles southward on Tuesday and Wednesday, allowing for
winds and seas to gradually subside.

Rip Currents / High Surf / Beach Erosion: Breakers will build to
the 4-5 foot range by this afternoon at the northeast FL beaches
and 3-4 feet at the southeast GA beaches. This rough, pounding
surf will create a high risk of deadly rip currents at all area
beaches from today through at least Monday, with astronomically
high tides adding to the danger, especially during the outgoing
tide during the late morning and early afternoon hours. Breakers
will build to the 5-6 foot range on Saturday at the northeast FL
beaches and 4-5 feet at the southeast GA beaches, with beach
erosion likely increasing during each high tide cycle during the
weekend.

&&

.HYDROLOGY...
Issued at 301 AM EDT Fri Oct 18 2024

Tides from the "super moon" continue to interact with already
elevated water levels and breezy onshore flow for the NE FL
Coastline and St. Johns River Basins, resulting in persistent,
long duration Coastal Flood Advisories and Warnings. Coastal
Southeast GA remains in the Coastal Flood Advisory as well through
the high tide this morning, though levels are expected to lower
for this area into the weekend. These elevated conditions for the
NE FL Coast and St. Johns River have been extended into Saturday,
and may need to be extended into Sunday as well. The gradual
subsiding of the higher than normal Super-Moon tides should help
any flooding into the weekend remain at minor levels along the
Atlantic Coast and lower St. Johns River in the JAX metro area, so
not expecting to issue any Coastal Flood Watch issuance at this
time, but will continue to monitor trends in the PETSS guidance
with each model cycle. Moderate flooding is expected to continue
around times of high tide through early next week for locations
in southern portions of the St. Johns River basin in eastern
Putnam and western Flagler Counties.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  74  46  75  50 /   0   0   0   0
SSI  71  57  74  62 /   0   0   0   0
JAX  74  56  77  62 /  10  10  20  10
SGJ  76  66  78  68 /  30  20  20  10
GNV  77  58  78  61 /  10  10  20  10
OCF  78  60  81  64 /  10  10  20   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 2 PM EDT Sunday for FLZ033-124-125-
     132-133-138-225-325.

     Coastal Flood Warning until 5 AM EDT Sunday for FLZ038-137.

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

GA...High Rip Current Risk through late Sunday night for GAZ154-166.

     Coastal Flood Advisory until 1 PM EDT this afternoon for GAZ154-
     166.

AM...Small Craft Advisory from 5 PM this afternoon to 5 AM EDT
     Saturday for AMZ450-452-454.

     Small Craft Advisory from 5 PM this afternoon to 5 PM EDT Monday
     for AMZ470.

     Small Craft Advisory until 5 PM EDT Monday for AMZ472-474.

&&

$$