623
FXUS62 KJAX 201735
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
135 PM EDT Sat Jul 20 2024

...New AVIATION...

.UPDATE...
Issued at 1010 AM EDT Sat Jul 20 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

Sunny to partly sunny skies at this time with a few bands of
cirrus clouds moving northeast over the area. Like yesterday, a
moist-laden airmass continues with PWAT of 2.18 inches measured
from JAX sounding. Should see plenty of cumulus forming in the
late morning and aftn with numerous to widespread showers and
storms forming by mid to late today. Current radar mosaic shows
scattered convection across the central and western FL panhandle.
The HRRR and the ARW Models are in good agreement showing showing
first convective activity forming over the western zones along
west coast sea breeze boundary and thermal troughing. Mean layer
flow a bit faster than yesterday at about 15-18 knots through 500
mb. This may slightly support chances of some semi- organized
clusters of storms, with strong gusty winds, frequent lightning,
and locally heavy rainfall. Isolated severe storms are possible,
with wind damage threat the main concern. The heavier rainfall
areas will likely be along the east coast where max convergence is
located due to the southwest prevailing flow meeting up with an
east coast sea breeze that may make it inland by 4-6 pm to near
the St Johns River in northeast FL and in southeast GA to near
Jesup and Woodbine. The main forecast updates were to lower rain
chances at least initially, but still forecasting upwards of 60-80
percent rain chances through the early evening hours. Max temps
generally unchanged in the lower 90s with heat indices briefly
around 108 but currently thinking too short duration for heat
advisory at this time. Slightly adjustment for min temps tonight
given the southwest, moist flow.

For the marine forecast, only minor adjustments for the winds and
seas, with observed seas at 41112 and 41117 currently 1 foot or so
lower than forecast. Otherwise, main concern for boaters will be
the strong wind gusts from storms this aftn and evening along with
the lightning threat.

&&

.NEAR TERM...
(Today and Tonight)
Issued at 322 AM EDT Sat Jul 20 2024

Southwest steering flow at the surface and in the mid levels
combined with atmospheric PWATs around 2 inches will continue a
near repeat of conditions from yesterday as late morning/early
afternoon convection over inland areas that will track East to
Northeast at 15-20 mph and reach the East Coast sea breeze that
should reach into the US 17 and I-95 corridors in the mid/late
afternoon hours and expect this convergence to trigger numerous to
widespread showers and storms with strong/gusty winds to 50 mph
along with heavy rainfall/localized flooding and frequent
lightning, and similar to yesterday isolated severe storms with
potential downburst winds to 60 mph are possible, mainly along the
I-95 corridor of the Atlantic Coastal counties where storm
mergers with the East Coast sea breeze are expected. This activity
should then continue at strong to isolated severe levels as it
pushes E-NE through the Atlantic Coastal Counties through the
early evening hours and into the Atlantic Coastal waters around or
just after sunset, with convection fading towards the late
evening hours and ending by midnight. Timing of the onset of
convection will determine eventual daytime Max temps, but overall
expect widespread lower to middle 90s inland and around 90F at the
Atlantic beaches and these combined with dewpoints into the
middle 70s should push heat indices into the 104-108F range,
likely just below or just briefly reaching Heat Advisory levels at
this time. Overnight lows in the 70s over inland areas and near
80F at the Atlantic beaches.

&&

.SHORT TERM...
(Sunday through Monday night)
Issued at 322 AM EDT Sat Jul 20 2024

A shift in the high pressure to the north-northeast of the region
on Sunday will see the overall flow shift to be primarily from
the south. This will allow the Gulf and Atlantic sea breezes to
venture well inland. The daytime heating will see the development
of showers and storms along the breezes, with activity picking up
as the sea breezes merge during the afternoon between the I-75 and
I-95 corridors. Most activity will dwindle during the overnight
hours due to the loss of the daytime heating.

By Monday, a southeasterly flow will become established as the
high pressure shifts further north-northeast. This will setup the
Atlantic sea breeze moving further inland towards the west. Near
the I-75 corridor will be the likely area for the merger between
the Gulf and Atlantic sea breezes during the afternoon hours on
Monday, setting up the development of the stronger showers and
storms of the day.

Early afternoon showers will keep temperatures in check in the
lower to mid 90s. Heat index values currently expected to stay
just below criteria for heat advisory at this time for the
weekend, but higher values will be expected along the coast.

&&

.LONG TERM...
(Tuesday through Friday)
Issued at 322 AM EDT Sat Jul 20 2024

The high pressure to the northeast will continue the pattern of a
far westward traveling Atlantic sea breeze. Showers and storms
will develop along the Atlantic sea breeze as it moves to the
west, but most convective activity likely to occur along the
merger of the sea breezes over the western portion of the area.
Activity will diminish each evening as the daytime heating is
loss. Temperatures will trend near to above normal with highs in
the low-mid 90s and lows in the 70s.

&&

.AVIATION...
(18Z TAFS)
Issued at 125 PM EDT Sat Jul 20 2024

VFR clouds around at this time. A few showers and thunderstorms began
to develop by about 16z-17z. Have continued to advertise TEMPO groups
for TSRA this afternoon and into the evening, with just a slight
adjustment to delay timing near CRG, JAX, and SSI. Showers and
storms may contain brief wind gusts and low vsby to MVFR and IFR
in heavy rainfall. The activity will concentration near or over
the TAFs mainly in the 21z-01z time frame and then move offshore
after about 02z. Mainly VFR overnight except for some MVFR vsby
currently shown for VQQ. A repeat can be expected again Sunday for
showers and storms, mainly aftn hours again.

&&

.MARINE...
Issued at 322 AM EDT Sat Jul 20 2024

No headlines expected over the next 5 days as high pressure ridge
from the Western Atlantic will be across or just south of the
local waters through early next week. This will continue a general
south to southwest flow through the period at 10-15 knots with
seas 2-4 ft, along with daily sea breeze along the local beaches
from the Southeast. A few evening/nocturnal southerly wind surges
could briefly reach into the 15-20 knot range, but not likely to
last long enough to warrant any headlines. Main impacts will be
offshore moving storms during the afternoon and evening hours with
strong/gusty winds to 30-45 knots, heavy rainfall and dangerous
lightning.

Rip Currents: Marginal moderate risk of rip currents will
continue through the weekend as mainly south to southwest flow
becomes briefly onshore Southeasterly during the afternoon hours
at the local beaches with surf/breakers of 2-3 ft.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  73  92  73  93 /  60  80  40  60
SSI  76  89  77  91 /  70  60  40  50
JAX  74  93  75  94 /  60  70  30  60
SGJ  75  93  76  92 /  70  60  20  50
GNV  73  93  73  93 /  40  80  20  80
OCF  73  94  75  93 /  40  80  20  80

&&

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

$$