173
FXUS62 KJAX 241913
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
313 PM EDT Tue Sep 24 2024

...TROPICAL STORM HELENE IMPACTS BEGINNING AS EARLY AS WEDNESDAY
NIGHT...

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

.NEAR TERM...
Issued at 310 PM EDT Tue Sep 24 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

Clear skies and easterly winds will continue tonight, with lows
falling into the lower to mid 70s tonight. Regarding Tropical
Storm Helene, a Hurricane Watch remains in effect for the I-75
corridor, and a Tropical Storm Watch for eastern Marion county.

&&

.SHORT TERM...
(Wednesday through Thursday night)
Issued at 310 PM EDT Tue Sep 24 2024

Tropical storm Helene will be lifting northward over the northwest
Caribbean and then the Gulf of Mexico Wed morning and early aftn,
with some acceleration northward. Based on the NHC forecast, the
system will be tracking northward Wed night and Thursday morning,
and basically paralleling the FL west coast during midday Thursday
as a Cat 2 to 3 and then making a landfall around the FL Big Bend
Thursday evening. Slight adjustments to track are expected
through the duration of the event, especially given the current
state of the system being in the formative stages of development.
For sensible weather on Wednesday, a few bands of showers will
likely be ongoing by midday Wednesday with surface winds also
increasing from the southeast. Some rotation in some showers
possible but overall not too favorable just yet for tornado
potential but will need to monitor closely. We could see some
favored areas for a rotating shower/storm along the coastal
counties where instability would be higher. Wed night, precipitation
becomes more widespread with some better potential for rotation
in some cells given the increasing shear, but again instability
will be pretty lacking for any robust shower or storm that would
produce a tornado, and, if any, appears to be across the coastal
counties primarily. Rainfall amounts Wed will mostly be confined
to northeast FL, but probably near or below 1 inch. Wed night,
rainfall amounts are more widespread at about 1-2 inches and a few
locales of 2-3 inches.

Thursday, tropical system Helene is forecast to be over the east
central Gulf of Mexico in the morning and be heading north-northeast
about 16 mph but picking up a little forward speed northward. The
landfall is projected to be in the evening. Tropical storm conditions
will be possible for many counties as the pressure gradient
associated with this system. Hurricane conditions possible over
the far western counties and watches are already in place. There
will be an elevated tornado threat for most of the area being in
the favorable eastern semicircle of the cyclone, and sufficient
instability given dewpoints in the lower to mid 70s. Additional
rainfall amounts Thursday look to be in the 1-3 or 2-4 inch range.

Thursday night, Helene forecast to track northward over the FL
Big Bend with strong winds raking across portions of the area and
Tropical storm conditions likely, and potential hurricane
conditions mainly west zones. The winds should diminish toward the
early morning hours.

Key Message to Remember: Review your plans and ensure necessary
supplies are assembled in the event of tropical storm or hurricane
impacts later later this week. Please pay close attention to the
forecast information locally as well as from the National
Hurricane Center to stay abreast of the latest forecast
information.

&&

.LONG TERM...
(Friday through next Tuesday)
Issued at 310 PM EDT Tue Sep 24 2024

Helene will continue to quickly leave the region with a residual
trough over the area southwest to northeast. Much lower rain
chances are anticipated. Flow will be southwesterly and initially
dry air Friday but moisture begins to advect back in from the
south and southwest leading to enhanced chances of showers for the
weekend into early next week. There is uncertainty on additional
rainfall amounts with the GFS and ECMWF a bit different for their
respective rainfall footprint. Leaning toward a wetter scenario
than what the GFS is suggesting. We could see some additional
rains of about 1-2 inches but more localized than widespread.
Despite this, we could see some localized flooding after Helene is
done over the area. Temperatures will trend down initially and
are expected to hover in the 80s for high temperatures due to
prevailing cloudiness and waves of rainfall.

&&

.AVIATION...
(18Z TAFS)
Issued at 100 PM EDT Tue Sep 24 2024

VFR conditions expected through this TAF period. Tropical Storm
Helene will cause conditions to deteriorate beginning Wednesday
evening.

&&

.MARINE...
Issued at 310 PM EDT Tue Sep 24 2024

A weak pressure pattern and light onshore flow continues today.
Small Craft Advisory conditions expected to develop during the
evening hours on Wednesday with the approach of Potential Tropical
Cyclone Nine in the gulf on Wednesday morning, winds will
continue to strengthen with tropical storm conditions possible by
early Thursday and continue into Friday morning. Some gradual
improvement on Friday as the system pulls away to the north. A
trough may linger over the region Friday night into the weekend
with winds and seas below small craft advisory levels.

Rip Currents: Moderate rip current risk today, high risk beginning
tomorrow for NE FL and SE GA beaches.

&&

.HYDROLOGY...
Issued at 310 PM EDT Tue Sep 24 2024

The Flood Watch has been expanded to include all of southeast
Georgia and northeast Florida. Excessive rainfall due to a
Tropical Storm Helene will likely result in scattered areas of
flash flooding and isolated episodes of considerable flash
flooding, specifically in urban flood prone locations and areas
that received a lot of rainfall this month. Widespread 3-6" of
rain is forecast, with locally higher amounts. Strong
southeasterly flow in response to the tropical system may bring
tidal levels back into Minor or low-end Moderate flood at times of
high tide along the Atlantic coast by Thursday evening. Given the
current elevated tides already ongoing in the St Johns River, the
potential for Moderate Flooding and impacts are possible during
at least Thursday and Friday high tides.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  70  88  72  81 /   0  20  50  90
SSI  77  85  76  83 /   0  10  50  80
JAX  74  88  76  85 /   0  30  60  90
SGJ  76  88  76  86 /   0  30  70  90
GNV  72  89  74  83 /   0  40  70 100
OCF  73  90  76  85 /   0  50  70  90

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Hurricane Watch for FLZ021-035-220-236-340-522.

     Flood Watch from Wednesday evening through Friday morning for
     FLZ021-023-024-030-031-033-035-038-120-124-125-132-133-
     136>138-140-220-225-232-236-237-240-322-325-340-422-425-522.

     Coastal Flood Advisory until 5 PM EDT Wednesday for FLZ033-038-
     125-132-137-225-325.

     Tropical Storm Watch for FLZ140-240.

GA...Flood Watch from Wednesday evening through Friday morning for
     GAZ132>136-149-151>154-162-163-165-166-250-264-350-364.

AM...None.
&&

$$