171
FXUS62 KJAX 041723
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
123 PM EDT Thu Jul 4 2024

...New NEAR TERM, AVIATION...

.UPDATE...
Issued at 759 AM EDT Thu Jul 4 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

Extended the Heat Advisory into all areas of the Suwannee Valley
west of Interstate 75. With their proximity to Gulf moisture felt
the humidity factor warranted an extension.

&&

.NEAR TERM...
Issued at 114 PM EDT Thu Jul 4 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

The frontal boundary/surface trough is quickly becoming more
diffuse this afternoon and looking at radar and visible satellite
imagery the Atlantic Sea Breeze front is becoming active with
convection firing between the ocean and St Johns River/U.S. 301 in
GA. The Gulf sea breeze is still west of U.S. 19 and have delayed
activation of that boundary until later this evening. Have
tweaked the forecast to reflect the east coast convection slowly
moving inland and converging near I-75 later this evening.

&&

.SHORT TERM...
(Friday through Saturday night)between the ocean and St Johns River/U.S. 301 in
GA.Issued at 400 AM EDT Thu Jul 4 2024

During this period, mid level high pressure at 500 mb will dominant
the region while the lo level ridge drops a bit further south and
southeast. Drier air will continue to filter in from the
northeast on Friday resulting in lower rain chances for the
coastal areas possibly just supporting slight rain chances there.
Further inland, we continue to show chance to likely POPs as the
sea breezes merge across the inland areas near and west of Highway
301 and I-75. A combination of max temps in the mid 90s and rich
dewpoints inland zones on Friday could result in another case for
some heat advisories. Isolated to scattered mainly evening convection
expected Friday night mainly across the inland zones. Lows in the
mid 70s to near upper 70s toward the coast are expected.

Saturday, some subtle pattern change as a mid level trough around
700 mb is forecast to come across AL and GA and help shove the
drier air along the eastern zones offshore. This in combination
with PWATs of about 2.2 inches or better will bring on more
scattered and numerous showers and storms to the forecast area,
possibly including the coastal zones. Max temps rise to mid 90s
and heat advy criteria could be met in some locations for brief
periods of time.

As far as t-storm environment, the local measured temps at 500 mb
are rather warm. JAX observed soundings have been averaging 500 mb
temps at -4 to -5 C for several days (about 2.5 deg warmer than
normal) and 850-500 mb lapse rates are about 5 C/km. This will not
change appreciable through Saturday and in fact may nudge even
warmer. PWAT values have also been averaging at least 2 inches
since June 28th. This will continue to support warm rain processes,
thus more heavy rainfall potential (mainly inland zones) given
the rather high PWAT air in place and slow storm motion. Certainly,
water loading and some localized dry pockets aloft may result in
gusty winds of about 35-50 mph in stronger storms.

&&

.LONG TERM...
(Sunday through Wednesday)
Issued at 400 AM EDT Thu Jul 4 2024

Models generally agree on low level ridge across north central FL
largely dominating the area and low level troughing across the
southeast states. The synoptic flow is weak enough for sea breezes
each day and more than sufficient moisture for daily scattered to
numerous showers and storms. Will keep POPS of about 40-70
percent each day. The hot and humid conditions are still
anticipated with little change in the dewpoints and the max temps
of mid 90s. Thus, we may see some areas with heat related
headlines during this period.

&&

.AVIATION...
(18Z TAFS)
Issued at 114 PM EDT Thu Jul 4 2024

The frontal boundary/surface trough is quickly becoming more
diffuse this afternoon and looking at radar and visible satellite
imagery the Atlantic Sea Breeze front is becoming active with
convection firing in the vicinity of KJAX-KCRG_KVQQ and KSGJ. The
Gulf sea breeze is still west of U.S. 19 and have delayed
activation of that boundary until later this evening with
convection delayed for KGNV until later this evening.

&&

.MARINE...
Issued at 400 AM EDT Thu Jul 4 2024

The weakening frontal boundary will move southward and dissipate
over the local waters today, with prevailing onshore winds
continuing as weakening high pressure lingers off the eastern
seaboard. Storm coverage will decrease Friday through Saturday,
with prevailing winds then shifting to southwesterly during the
weekend ahead of the next slowing frontal boundary approaching
from the north.

Rip Currents: Given the area rescues and surf noted yesterday of
up to 2-4 ft, High Risk was elected to be posted for NE FL beaches
today and then becoming Moderate on Friday. Moderate Risk for SE
GA beaches through Friday.

&&

.CLIMATE...
Issued at 400 AM EDT Thu Jul 4 2024

Above average max/min temps expected through Saturday with the
record high mininim not too far off the forecast min temps
in the mid 70s.

July 4:
KJAX: 78/1997
KGNV: 77/1897

July 5:
KGNV: 75/2023

July 6:
KJAX: 79/1902
KGNV: 78/1900

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  93  74  95  75 /  40  10  50  30
SSI  90  78  92  79 /  30  10  20  10
JAX  92  75  94  75 /  40  20  30  10
SGJ  91  77  92  76 /  40  20  30  10
GNV  92  73  94  74 /  60  30  60  20
OCF  93  75  93  75 /  70  40  60  20

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Heat Advisory until 6 PM EDT this evening for FLZ021-035-038-136-
     137-140-220-236-237-240-340-522.

     High Rip Current Risk through late tonight for FLZ124-125-133-
     138.

GA...None.
AM...None.
&&

$$