233
FXUS62 KJAX 171731
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
131 PM EDT Tue Sep 17 2024

...New AVIATION...

.NEAR TERM...
Issued at 1015 AM EDT Tue Sep 17 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

Finally, a quiet day for the region as far as rainfall is concerned!
We should only see some scattered low cloudiness and a few pop up
showers across the forecast area this afternoon and this evening.
Some locally dense fog after midnight for the interior areas from
about the St Johns River/U.S. highway 1 in GA westward. The
biggest thing going on today will be the continuation of minor to
moderate coastal flooding about 1-2 hours either side of high
astronomical tide.

&&

.SHORT TERM...
(Wednesday through Thursday night)
Issued at 333 AM EDT Tue Sep 17 2024

The cutoff trough that was once Potential Tropical Cyclone #8
will meander over the southern Appalachians on Wednesday, with
the base of this trough swinging eastward across our region
during the afternoon and evening hours. Meanwhile, a stubborn
frontal boundary that has been nearly stationary across the FL
peninsula and panhandle during the past several days will lift
north of our area, placing our region in a seasonably warm and
humid air mass. Scattered convection is expected to develop
along mesoscale boundaries such as the Gulf and Atlantic sea
breezes during the afternoon hours, with deep west-southwesterly
flow tending to focus mesoscale boundary collisions along the
I-95 corridor during the late afternoon and early evening hours.
Colliding mesoscale boundaries may allow for a few storms to
pulse and become strong as they intersect the pinned Atlantic
sea breeze boundary along the coast during the late afternoon
and early evening hours, with stronger storms being capable of
producing downburst winds of 40-50 mph, along with slow moving
downpours and frequent lightning strikes. Highs will climb to
the upper 80s to around 90, with a few lower 90s possible in
north central FL. Maximum heat indices will reach the 95-100
degree range in the early to mid afternoon before convection
and cloud cover become more widespread during the late
afternoon.

Evening convection may linger along the I-95 corridor to the
south of Jacksonville and across north central FL, with
activity then pushing offshore or towards the I-4 corridor
before midnight. Flow aloft will shift to a more
west-northwesterly direction overnight following the passage
of the base of the aforementioned trough through our area,
which will advect a drier air mass into our region. Lows will
fall to the upper 60s to lower 70s inland, ranging to the low
and mid 70s at coastal locations.

Troughing will lift northeastward towards the Mid-Atlantic
region on Thursday, finally pushing the stubborn frontal
boundary southeastward across our area as deep-layer flow
veers to northwesterly. A drier air mass will continue to
advect across inland southeast GA and northern portions of
the Suwannee Valley, but enough moisture may be in place for
isolated to widely scattered afternoon and early evening
convection to develop along the frontal boundary as it
crosses coastal southeast GA and the rest of northeast and
north central FL. Highs on Thursday will again climb to the
upper 80s and lower 90s, with maximum heat indices peaking
in the 95-100 degree range during the afternoon hours.

Convection that manages to develop during the afternoon
hours should push offshore of the northeast FL coast towards
sunset, with fair skies expected area-wide overnight. A
drier and more subsident air mass may allow for areas of
locally dense fog to develop by early Friday morning,
especially across inland portions of southeast GA and the
Suwannee Valley. Lows will again fall to the upper 60s and
lower 70s inland, ranging to the lower 70s at coastal

&&

.LONG TERM...
(Friday through Monday)
Issued at 333 AM EDT Tue Sep 17 2024

Troughing aloft will persist along the New England and
Mid-Atlantic coast on Friday and Saturday, while stout
ridging centered over Texas and the southern Plains
states late this week begins to flatten as it expands
eastward along the northern Gulf coast this weekend.
Surface low pressure may strengthen off the Mid-Atlantic
coast as it meanders this weekend, while strong high
pressure building over Quebec and Atlantic Canada begins
to expand down the U.S. eastern seaboard. This weather
pattern will eventually tighten our local pressure
gradient during the weekend, although there are timing
differences at this point in the extended guidance.
Model blends currently depict northeasterly low level
flow developing locally on Friday and then gradually
strengthening as the weekend progresses. This flow may
advect isolated to widely scattered showers and possibly
a few embedded thunderstorms onshore along the northeast
FL coast, with activity potentially shifting inland
towards north central FL during the afternoon hours
each day. An overall drier and more subsident air mass
will prevail for southeast GA and the Suwannee Valley,
where a dry stretch of weather appears likely from Friday
through at least Monday.

Breezy onshore winds during this period should keep
coastal highs in the low to mid 80s, with mid to upper
80s forecast for most inland locations. Highs may
trend down a few degrees by Monday across inland
southeast GA as high pressure wedges into the Deep
South. The drier and more subsident air mass will allow
lows to fall to the mid to upper 60s at most inland
locations through the period, while onshore winds keep
coastal lows in the low to mid 70s.

&&

.AVIATION...
(18Z TAFS)
Issued at 122 PM EDT Tue Sep 17 2024

Abundant Cumulus cloud deck development across NE FL this
afternoon with most CIGS in the 3500-4000 ft range, but a few
brief MVFR CIGS of 2500-3000 ft still possible for a few hours at
SGJ, but overall VFR with light winds. Rainfall chances remain
fairly low at SGJ/GNV but will leave in VCSH until 00Z for
consistency for now. After sunset mainly VFR conds with low
rainfall chances although a few Hi-res models are suggesting a few
sprinkles possible with old frontal boundary lifting northward but
will continue to leave out of forecast for now and focus on
potential fog formation at inland TAF sites with IFR VSBYS
expected at GNV/VQQ in the 08-13Z time frame and MVFR VSBYS at JAX
from 09-12Z. Mixed solutions for Wednesday morning but expect SCT
clouds around 2500ft from 14-18Z, as well as potential for
rainfall chances at SSI with the frontal boundary, so have added
VCSH in this time frame with the new TAF package.

&&

.MARINE...
Issued at 333 AM EDT Tue Sep 17 2024

Winds and seas subside today as a subtropical low pressure system
weakens over the Carolinas. A leftover frontal boundary and weak
pressure pattern will linger over the region through the middle of
the week. The sea breeze returns with afternoon wind shifts to
onshore for the nearshore waters through Thursday. A frontal
passage is expected late this week with high pressure building
north of the region by this weekend and will lead to an increase
in Northeast winds by Friday and Saturday.

Rip Currents: Rough surf (4 to 6 ft) and onshore winds in the
afternoon will result in high risk of rip currents continuing for
area beaches today. Winds and seas subside with a moderate risk
anticipated for Wednesday.

&&

.HYDROLOGY...
Issued at 333 AM EDT Tue Sep 17 2024

High astronomical tides with the upcoming full moon, trapped
tides and runoff from recent heavy rainfall will continue minor to
moderate coastal flooding along the St. Johns river through at
least mid-week. Waves begin to subside today but minor flooding
will continue along the Atlantic coast and ICWW. Peak tidal levels
will generally be in the 1.5 to 2.3 ft range above MHHW along the
St. Johns River Basin and the Atlantic coast.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  85  68  88  69 /   0  10  30  10
SSI  83  73  87  72 /   0  10  50  50
JAX  87  72  90  71 /  10  20  60  50
SGJ  85  74  89  72 /  20  20  60  50
GNV  87  71  90  70 /  30  10  50  20
OCF  89  71  91  71 /  30  10  50  10

&&

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

AM...None.
&&

$$