487
FXUS62 KJAX 181327
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
927 AM EDT Thu Jul 18 2024

...New UPDATE...

.UPDATE...
Issued at 840 AM EDT Thu Jul 18 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

A few tweaks to the forecast to lower max temps with lingering
cloud cover and stormy SW flow brining once again an earlier
start to convection today. Around 920 am, storms were already
approaching the I-75 corridor from the Gulf Coast region. Max
temps will top out in the upper 80s to near 90 across our western
zones to the low 90s toward the east before convection.

No major changes to the precipitation forecast with 60-75% rain
chances expected across the area today. Convection will once again
progress across NE FL through late afternoon, then develop across
SE GA into the afternoon and early evening south of a surface
front.

The main difference for today`s storms compared to yesterday is
there there may be a few stronger to isolated severe storms
especially near and north of the I-10 corridor as vertical lift
will be enhanced with an approaching mid level short wave trough,
which was already enhancing storms across SW GA this morning. Also
the 12z JAX RAOB showed slightly steeper mid level lapse rates
with 500 mb temps cooling to near -8 degC compared to -6degC
yesterday morning. Just a few knots of increased mid and upper
level westerly wind shear as well today compared to yesterday.

The main hazards in storms will continue to be gusty wet downbursts,
with magnitude potential a little stronger today with gusts of
40-60 mph possible. Locally flooding rainfall will continue to be
a concern, especially near the Altamaha River basin where rainfall
amounts yesterday neared 4-5 inches in parts of Coffee, Jeff
Davis and Appling counties.

Rainfall will tapper off with loss of diurnal instability and in
the wake of the departing short wave trough this evening, with dry
conditions expected after midnight and mild, but muggy lows in the
low to mid 70s. Some shallow ground fog and mist will be possible
toward sunrise especially where recent heavy rainfall occurred.

&&

.NEAR TERM...
Issued at 254 AM EDT Thu Jul 18 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

Any lingering convection over interior southeast GA has fizzled
over the past couple hours, with just some occasional leftover
debris clouds and a seasonably mild night tonight.

A cold front currently draped across the Ohio and Tennessee River
Valley area will make some pretty quick progress southward through
the rest of today ahead of its parent upper trough, both of which
will quickly start to lose momentum and stall north of the area by
tonight. This will push the surface ridge overhead a bit further
south and east, but also strengthen the mostly uniform flow aloft
slightly as well.

The main "take home" with all of this will be a similar regime as
seen over the past few days with a stacked southwest flow, earlier
onset to convective timing, and a sea breeze pinned around the
I-95 to the coast vicinity. The slightly stronger flow aloft will
certainly keep the threat for some strong storms across the area,
especially as convection from earlier in the day collides with the
Atlantic sea breeze during the afternoon. Wet downbursts in the
40-55mph range will be the primary hazard, and an isolated severe
storm also quite possible.

Temperatures are also expected to be similar to those seen on
Wednesday. The warmer southwesterly flow will be slightly offset
by the earlier start to convection and overspreading cloud cover
for many, resulting in highs forecast in the low to mid 90s.
Though depending on timing and coverage, some areas could under or
over achieve.

Similar to Wednesday, some showers and t`storms may linger over
interior southeast GA into the start of the overnight hours
tonight closer to the frontal zone mentioned above. Otherwise,
just some leftover clouds with lows in the mid to upper 70s.

&&

.SHORT TERM...
(Friday through Saturday night)
Issued at 254 AM EDT Thu Jul 18 2024

Predominant southwesterly steering flow that has been locked in
across the region through the majority of the week will shift and
prevail out of the south through Saturday as ridging rebuilds to
the east. Though there will be pockets off "drier" air (PWATs <
2"), for the most part abundant moisture will be available and
fuel scattered convection along the sea breezes, with coverage
blossoming inland as sea breezes merge.

Due to outflow and and other mesoscale boundary interactions,
it`s tough to discern where exactly the merger and stronger
convection potential will be. That said, placing the potential for
widespread showers and a few strong pulses roughly between the
Highway 301 and I-95 corridors on Friday. As flow shifts a bit
more southerly by Saturday, the merger should occur more inland,
generally between Highway 301 and I-75.

As has been the case with this moist airmass, concerns with
convection will be localized to areas flooding, particularly in
urban locations or where the grounds are still soaking in rain from
the last couple of days. Frequent lightning and gusty outflow winds
are also possible with deeper pulses, likely along the sea breeze
collision zone.

Before convective cooling occurs, temperatures will push into the
low 90s each day with the highest heat index readings near the coast
up to 105-108F.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 254 AM EDT Thu Jul 18 2024

The seasonably active thunderstorm period continues through Sunday
with a more progressive Atlantic sea breeze amid southeasterly flow.
Appears that an inverted shortwave or two will rotate around the
western extent of the stacked Bermuda ridge next week; these
features may serve to enhance storm chances further Monday and
possibly Tuesday, though it will depend on how fast and where they
track. Available moisture will retreat some toward the middle of
next week, potentially in the wake region of the aforementioned
shortwaves, and this may limit storm coverage during the middle part
of next week. Temperatures will trend near to above normal with
highs in the low-mid 90s and lows in the 70s.

&&

.AVIATION...
(12Z TAFS)
Issued at 712 AM EDT Thu Jul 18 2024

VFR conditions early this morning under FEW020-030 and BKN250. SW
winds increase after sunrise to 3-6 kts across all terminals.
Another active storm day is expected with TS approaching GNV by
15-17z from the west, and continuing to advance toward JAX and
VQQ with additional VCTS developing along the inland progressing
east coast sea breeze by 17-18z at CRG, SGJ and SSI as winds
transition to S to SSE with speeds 10-12 kts into the early
evening. Will monitor radar trends and add TEMPO groups at
terminals as needed later this morning and into the afternoon. As
was the case yesterday, locally heavy rainfall and gusty winds of
30-40 kts are possible today in stronger cells.

Convection will press offshore of the local Atlantic coast and
decrease in coverage from west to east through 22-01z. Lingering
debris clouds overnight with dry conditions by 06z. Potential for
MVFR due to shallow ground fog/mist after 07z 7/19 with a
land breeze from the SW 2-4 kts at coastal terminals through 12z
Friday.

&&

.MARINE...
Issued at 254 AM EDT Thu Jul 18 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. Showers and
thunderstorms will approach 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.

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.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  94  74  95  73 /  60  40  70  40
SSI  92  79  93  79 /  60  40  50  40
JAX  95  75  95  76 /  70  30  70  30
SGJ  93  77  93  77 /  60  30  50  20
GNV  92  74  93  73 /  70  20  80  20
OCF  93  74  93  75 /  70  20  80  30

&&

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

$$