573
FXUS62 KJAX 261059
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
659 AM EDT Thu Sep 26 2024

...New AVIATION...

.AVIATION...
(12Z TAFS)
Issued at 658 AM EDT Thu Sep 26 2024

Showers and storms will move through the area as outer rain bands
from Hurricane Helene push in from the south to north. Winds will
begin to pick up around 13Z-14Z, with gusts from 35kt to 40kt
possible with the stronger storms. Lower level WS possible at TAF
sites as the gusts get going. Activity will linger through much
of the TAF period, beginning to lessen near the end of the TAF
period.

&&

.NEAR TERM...
Issued at 354 AM EDT Thu Sep 26 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

Hurricane Helene will continue to move north across the Gulf of
Mexico today, making landfall sometime late this evening along the
Big Bend of Florida. Outer rain bands from Helene will move
through northeast Florida and southeast Georgia, bringing showers
and storms for most locations. Within any showers and storms,
there will be the potential for isolated tornadoes to develop over
inland locations with the rain bands. As low-level shear increases
and the large wind field of Helene spans across the Florida
peninsula, the highest potential for tornado development will be
along coastal Duval and northward along coastal locations of
southeast Georgia, with potential waterspouts possibly making
their way onshore with the southeasterly flow. General timing for
the increase potential for tornado development will be from 5pm to
11p. Highest winds away from the center of the system are
expected to occur along coastal sites, with gusts up to tropical
storm speeds (~65mph), with the Suwannee Valley region possibly
getting sustained winds up to Hurricane force speeds as Helene
nears and makes landfall. With the elevated southeasterly flow,
this will lead to the potential for waters from the upper St.
Johns to be pushed northward into the lower St. Johns which can
lead to flooding along the low-lying areas along the St. Johns
river, particularly downtown Jacksonville. In addition to the
wind threat, localized flooding for those locations which may
still have saturated soils as the past month has been one of the
wettest with record rainfall amounts. While rainfall totals have
trended down from earlier estimates, additional periods of heavy
rainfall will still be a factor for those locations with saturated
soils as well as low-lying poor drainage areas.

&&

.SHORT TERM...
(Friday through Saturday night)
Issued at 354 AM EDT Thu Sep 26 2024

Helene will continue to zip northward through the day Friday,
gradually transitioning to an extratropical system while merging
with an upper low near the Ohio River Valley. A dry slot aloft to
the south and southwest of the departing system works its way in
for Friday, which will generally limit rain chances for most of
the area as a developing frontal boundary sits just south of the
region. The best chance for any showers and perhaps some isolated
thunder will be south of about Gainesville to Saint Augustine, and
especially during the first half of Friday. The southwesterly flow
within the dry slot will be pretty breezy, with winds in the
15-20mph range and gusts up to 25-35mph. This flow direction
should also allow temps to climb to the upper 80s to near 90 near
the I-95 corridor and to the coast, with low to mid 80s over the
interior.

The same upper low essentially sits and spins almost in place near
the western Ohio River Valley Friday Night and through Saturday,
which should keep the southwesterly flow and some drier air into
the area through this time frame. There is some discrepancy
remaining with respect to where the exact moisture/frontal
boundary sets up and therefore extent of convection. However,
expecting at least slightly higher rain chances for parts of the
area Saturday, with again the best chances being south and west of
I-10 and south of Gainesville to Saint Augustine as with Friday.
Winds will settle down a bit compared to Friday, though still in
the 10-15mph range with gusts in the 20s. Temperatures will be
similar to Friday, upper 80s to near 90 south and east and mid 80s
north and west.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 354 AM EDT Thu Sep 26 2024

The remnant mid/upper low starts to broaden and elongate by the
end of the weekend and into the start of next week, eventually
drifting offshore the eastern seaboard around the Tuesday to
Wednesday time frame as a weakening trough. Similar to the start
of the weekend, certainly still some discrepancy with long range
guidance regarding extent of available layer moisture and the
position of a nearly stalled front. Given the overall wet pattern
of recent and lingering dynamics with the upper low/trough,
leaning towards chances of showers and storms continuing for
generally the southern half of the CWA for at least the start of
next week, possibly dropping lower by mid week if a more subsident
airmass builds in north and west of the departing upper feature.

Temperatures for this period start generally slightly above
normal, though trend closer to normal towards midweek. &&

&&

.MARINE...
Issued at 354 AM EDT Thu Sep 26 2024

Hurricane Helene continues to move northward through the gulf
early this morning. Southeasterly winds will gradually strengthen
through the day reaching tropical storm strength by the morning
hours, lingering at these levels into Friday. The tropical system
will begin to move away from the area sometime on Friday. With a
trough lingering over the area into the weekend, conditions are
not expected to be at small craft advisory levels.

Rip Currents: High risk of rip currents on for all area beaches
through Friday as southeasterly flow increases ahead of Hurricane
Helene over the Gulf of Mexico.

&&

.HYDROLOGY...
Issued at 354 AM EDT Thu Sep 26 2024

A Flood Watch for all of southeast Georgia and northeast Florida
is in effect. Excessive rainfall due to Hurricane Helene will
likely result in scattered areas of flash flooding and isolated
episodes of considerable flash flooding, particularly 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  82  72  85  66 /  90  90  10   0
SSI  85  77  88  73 /  80  80  10   0
JAX  86  77  90  72 /  80  80  20  10
SGJ  88  77  91  74 /  80  80  20  20
GNV  85  75  87  72 / 100  90  20  10
OCF  87  77  89  74 / 100  90  20  10

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Tropical Storm Warning for FLZ023-024-030-031-033-038-124-125-
     132-133-136>138-140-225-232-237-240-325-425.

     Flood Watch 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.

     Hurricane Warning for FLZ021-035-120-220-236-322-340-422-522.

     Coastal Flood Advisory until 8 AM EDT Friday for FLZ033-038-132-
     137.

     Coastal Flood Warning until 8 AM EDT Friday for FLZ124-125-133-
     138-225-325.

     High Rip Current Risk through Friday evening for FLZ124-125-133-
     138.

     High Surf Advisory until 4 PM EDT Friday for FLZ124-125-133-138.

GA...Tropical Storm Warning for GAZ133>136-151>154-165-166-250-264-
     350-364.

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

     Hurricane Warning for GAZ132-149-162-163.

     Coastal Flood Warning until 8 AM EDT Friday for GAZ154-166.

     High Rip Current Risk through Friday evening for GAZ154-166.

     High Surf Advisory until 4 PM EDT Friday for GAZ154-166.

AM...Tropical Storm Warning for AMZ450-452-454-470-472-474.

&&

$$