115
FXUS62 KJAX 180229
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
1029 PM EDT Wed Jul 17 2024

...SEASONABLY ACTIVE THUNDERSTORM PATTERN CONTINUES...

For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf

.UPDATE...
Issued at 1028 PM EDT Wed Jul 17 2024

Late evening surface analysis depicts the axis of Atlantic surface
ridging extending westward across north central FL. Meanwhile, a
frontal boundary extends from Atlantic Canada southward across New
England and the Mid-Atlantic states, with this boundary then
snaking its way through the Tennessee Valley and the Ozarks.
Aloft...mid-level ridging was centered over the FL peninsula,
creating a prevailing west-southwesterly flow pattern over our
region, while troughing was digging southeastward across the Great
Lakes region and the Ohio Valley, with the base of this trough
extending across the lower Mississippi Valley. Thunderstorm
activity that erupted over portions of inland southeast GA this
afternoon and earlier this evening continues to gradually wane,
with localized flooding beginning to diminish over portions of
Coffee and Jeff Davis Counties, where widespread 2-4 inch totals
occurred in a corridor from Douglas to Baxley and points north and
westward towards the Altamaha/Ocmulgee Rivers. Leftover mid and
high altitude debris clouds were in place elsewhere, with a few
light showers developing beneath this cloudiness across portions
of northeast FL. Temperatures ranged from rain-cooled lower 70s
across portions of inland southeast GA to the lower 80s along the
northeast FL coast, with dewpoints generally in the low to mid 70s
as of 02Z.

Stratiform rainfall will gradually wane across inland southeast
GA, mainly for locations north and west of Waycross and Jesup,
through around midnight before dissipating completely overnight.
Convection will likely begin to develop towards sunrise along the
FL Big Bend and Nature coasts as deep southwesterly low and mid
level flow continues, with isolated showers and thunderstorms
possibly moving onshore and approaching the Suwannee River shortly
after sunrise on Thursday. Otherwise, mid and high altitude debris
cloud cover will gradually thin overnight, with lows in the 70s
nearly area-wide.

&&

.SHORT TERM...
(Thursday through Friday night)
Issued at 247 PM EDT Wed Jul 17 2024

Elevated daily rain chances continue through Friday as SW steering
flow continues across the local area between the 1000-500 mb ridge
axis across south-central FL and weak troughs north of the region.
Morning showers and storms will edge inland from the Gulf Coast
region, expanding in coverage and progressing toward the Atlantic
coast through early afternoon as diurnal instability increases.
Additional convection will break across SE GA into the afternoon
and linger into the early evening closer to low level trough
trough axes and lingering outflow boundaries. Mid level
temperatures continue near climo values with -6 to -7 deg C at 500
mb with weak upper level shear (< 25 kts) so convective
ingredients continue to favor mainly pulse strong to isolated
severe storm potential in the afternoon and early evening with
boundary mergers. Storm motion of 10-15 kts will somewhat limit
the localized flash flood threat, but, storms are dropping 2-4
inches within 2 hours where mergers occur...so a couple days of
heavy rainfall could certainly cause localized flood issues.
Storms will fade across inland coverage toward midnight with loss
of instability, then resurrect toward the Gulf Coast toward
sunrise with some inland drift across our Suwannee River Valley
zones.

Temperatures will trend within a few degrees of climo values with
highs in the low-mid 90s and lows in the lower to mid 70s. Peak
heat index values near 105 deg each day prior to convective
cooling.

&&

.LONG TERM...
(Saturday through next Wednesday)
Issued at 247 PM EDT Wed Jul 17 2024

The ridge across south-central FL begins to build northward across
NE FL Saturday then shifts north of the local area Monday. This
will transition prevailing flow from SW over the next couple of
days to SSE this weekend then SE early next week, with a more
dominant east coast sea breeze pattern. Elevated rain chances with
locally heavy rainfall potential will continue through the weekend
with high PWAT trapped under the ridge axis and weak storm motion
(PWATs 1.9-2.25"). Monday through Wednesday night week, deep layer
moisture begins to decrease some into the 1.6-2 inch range
favoring more scattered shower and thunderstorm activity for most
inland areas (40-50% rain chances), then numerous (50-60%) where
sea breezes and boundaries merge during the afternoon and evening
near and west of I-75. Temperatures will trend near to above
normal with highs in the low-mid 90s and lows in the 70s.

&&

.AVIATION...
(00Z TAFS)
Issued at 811 PM EDT Wed Jul 17 2024

Periods of MVFR visibilities will be possible overnight at VQQ.
Otherwise, VFR conditions will prevail at the regional terminals
through at least 15Z on Thursday. Showers and thunderstorms
developing during the morning hours along the Gulf coast sea
breeze may approach the GNV terminal towards 16Z, with activity
then developing along a slower moving Atlantic sea breeze boundary
towards 18Z. Convection should then increase in coverage along the
Interstate 95 corridor after 19Z as outflow boundaries merge, with
a few strong thunderstorms possible at the regional terminals
through around 23Z. We included PROB30 groups at each terminal for
brief wind gusts around 30 knots and MVFR visibilities during
heavier downpours. Activity should shift east of GNV by 21Z and
will likely move offshore before 00Z Friday. Southerly surface
winds around 5 knots this evening will diminish overnight at the
inland terminals, with southwesterly winds then increasing to 5-10
knots at the terminals before 15Z. The Atlantic sea breeze
boundary is expected to move slowly inland on Thursday,
crossing the SGJ and SSI coastal terminals before 18Z and then
CRG towards 19Z, with southeasterly winds increasing to 10-15
knots outside of developing thunderstorm activity following the
passage of the sea breeze.

&&

.MARINE...
Issued at 1028 PM EDT Wed Jul 17 2024

The axis of Atlantic ridging will continue to extend westward
across the northeast Florida waters through Thursday, creating a
prevailing southerly wind flow across our local waters. Winds will
become onshore during the early afternoon hours on Thursday as
the sea breeze develops and pushes inland, followed by a southerly
evening wind surge that will likely bring speeds up to Caution
levels of 15-20 knots offshore. Seas of 2-4 feet will prevail both
near shore and offshore through the weekend.

Showers and thunderstorms will approach our local waters from the
west, possibly impacting the near shore waters by the mid to late
afternoon hours on Thursday. A frontal boundary will then sink
southward across the southeastern states on Friday, with this
feature stalling well to the northwest of our local waters during
the upcoming weekend. Showers and thunderstorms will likely
increase in coverage throughout our local waters during the
weekend and early next week before the axis of Atlantic ridging
lifts northward, placing our local waters within a prevailing
southeasterly wind flow towards the middle portion of next week.
Seas will build to the 3-5 foot range over the offshore waters
early next week as a more persistent onshore wind regime develops.

Rip Currents: Developing onshore winds during the early afternoon
hours will combine with a persistent east southeasterly ocean
swell to create a lower-end moderate risk at all area beaches
through at least Friday.

&&

.FIRE WEATHER...
Issued at 1028 PM EDT Wed Jul 17 2024

Southwesterly transport winds will become breezy for locations
along and north of the Interstate 10 corridor by early Thursday
afternoon. These breezy transport winds will combine with elevated
mixing heights to create good daytime dispersion values, while
lighter south-southwesterly transport winds will generally result
in fair daytime dispersion values for locations south of I-10. A
similar weather pattern will prevail on Friday, with elevated
mixing heights possibly resulting in marginally high daytime
dispersion values across portions of inland southeast GA. Elevated
mixing heights will combine with mainly southerly transport winds
to create good daytime dispersion values at most inland locations
on Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  75  95  74  94 /  30  40  30  70
SSI  80  93  80  93 /  10  30  30  70
JAX  75  95  76  95 /  10  60  20  80
SGJ  77  92  78  93 /  30  50  20  70
GNV  74  93  75  95 /  20  60  10  80
OCF  74  93  75  94 /  10  50  10  90

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&

$$