235
FXUS62 KJAX 210037
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
837 PM EDT Thu Aug 20 2026

.KEY MESSAGES...

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

- Heat Advisories for Portions of NE FL Friday

- Numerous Afternoon and Evening TStorms on Friday & Saturday

- Isolated to Scattered Afternoon & Evening TStorms Sun - Wed

&&

.NEAR TERM /THROUGH TONIGHT/...
Highlights through Tonight:

- Near Record High Temperatures Continue Today with Dangerous Heat
Indices for Portions of Our Area. Heat Advisories in Effect from 11
AM through 7 PM Today for Locations South and East of Waycross, GA.

- Strong to Isolated Severe Thunderstorms are Possible this
Afternoon and Evening Across Northeast and North Central FL. Wet
Microburst Potential Will Exist within Stronger Storms, Creating
Wind Gusts of 40-60 mph, along with Frequent Lightning Strikes and
Localized Flooding.

A cold front north of the area extending from the SC coast westward
into central GA while weak surface high pressure is over the north
half of the Gulf. Weak west to northwest winds 4-8 mph are observed
across the area between the two surface features. Satellite imagery
this morning shows a swirl of mid to high level clouds over north
central and central FL denoting the center of the mid/upper level
low across the FL peninsula. GOES Satellite estimates of Total
Precipitable Water level (PWATs) indicates some of the drier air
over SE GA this morning has begun to erode south of Waycross to near
2 inches, but drops off into with PWATS in the 1.40 to 1.60 inch
range along and north of US-82 to the Altamaha river and northward
to near the surface front while over 2.0 inches over NE FL.

This morning`s 12Z upper air sounding revealing high moisture level
of 2.08 inches of Precipitable Water (very close to the 90th
percentile based on climatology) and fairly moist low to mid levels
with some drier air above 500 mb as well as slightly cooler 500mb
temps -7 to 8C. The cooler mid level temperatures and high moisture
levels will support stronger mid level lapse rates with as seen by
800 to 600 mb level lapse rates around 7.0 C/km. While the sounding
also convective temperature is 94 degrees, abundant sunshine today
will allow temperatures to quickly reach the mid 90s and allow the
onset of scattered showers and isolated thunderstorms by 12PM-2PM
period as the Gulf seabreeze pushes towards I-75, then 2-4PM along
the Atlantic seabreeze as it moves onshore towards I-95.

As the Atlantic seabreezes continues inland this afternoon strong
heating, shortwave energy aloft, and interactions from shower and
thunderstorm outflows with the Atlantic/Gulf seabreezes will spur
scattered to numerous thunderstorms. Isolated strong to marginally
severe thunderstorms will develop along storm mergers and outflow
collisions focused from highway 301 to to US-17 with main impacts
being wet downbursts producing wind gusts 40-60 mph, frequent
lightning, and locally heavy downpours. Slow storm motions will
create slow moving, torrential downpours with heavy rainfall rates
of 2-3 inches per hours leading to locally 1-3 inch quick rainfall
totals that could lead to minor flooding over urban, low-lying, and
poor drainage areas. Westerly winds will turn west southwesterly 5
to 10 mph, switching to east to southeasterly behind the Atlantic
seabreeze 8-12 mph with gust 15 to 20 mph at the beaches.

Hot west to southwest flow in the low levels over the area will push
high temperatures into the mid to upper 90s over NE FL while drier
air and lack of thunderstorm coverage across much of SE GA will
allow highs to soar into the upper 90s to around 100s. Highs will
approach within a couple of degrees of daily record highs today,
through likely stay just below. While dewpoints will mix to the mid
to upper 60s over most of SE GA along and north of US-82, higher
humidity from dewpoints in the mid to upper 70s will make feels like
temperatures soar into the 108 to 112 degrees. These dangerous heat
index values will also lead to Major heat risk affecting anyone
without cooling/hydration. Therefore, a heat advisory is in effect
today through 7PM south of US-82 over inland SE GA, the SE GA coast,
and all of NE FL.

Tonight, thunderstorms will continue to persist just past sunset
through 9-10PM before waning in coverage and intensity inland.
Scattered showers will continue underneath remaining mid to high
level storm clouds before dissipating by midnight. Skies will become
mostly clear after midnight with shallow ground fog forming over
localized areas that received heavy rainfall. Lows will fall to the
low/mid 70s west of I-95, mid 70s along I-95, upper 70s along the
coast and St Johns river.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Main Highlights This Period (Friday and Saturday):

- Heat advisories posted for coastal areas of NE FL Friday

- Strong to possibly severe thunderstorms possible Friday and
Saturday

A weak surface low will remain centered over the Carolinas, with an
associated frontal boundary extending across Georgia. An upper
trough will move into the region Friday and remain overhead
Saturday, increasing instability and supporting above-normal chances
for afternoon and evening thunderstorms. Temperatures will remain
near to slightly above average.

Friday: The heat wave will persist, with Heat Advisory is posted for
coastal areas of NE FL as heat index values reach 105109F ahead of
convection. Increasing instability ahead of the upper trough,
combined with precipitable water values of 2.102.40 inches, will
support numerous afternoon and evening showers and thunderstorms.
This environment will favor locally strong to severe storms, with
strong instability and weak shear supporting microbursts, gusty
outflows, frequent lightning, and locally heavy rainfall. Scattered
to widespread convection is expected Friday afternoon and evening.
Lows will be in the mid 70s.

Saturday: The upper trough will remain overhead, resulting in
increased coverage of afternoon and evening thunderstorms, with rain
chances generally 6070% south of Waycross. Greater storm coverage
should provide some relief from the most extreme heat, with heat
index values of 102106F and highs in the lower to mid 90s.
Stronger storms will remain possible, with frequent lightning, gusty
winds, and locally heavy downpours. Lows will be in the lower to mid
70s.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Main Highlights This Period (Sunday through Wednesday):

- Strong to possibly severe thunderstorms possible each afternoon
and evening

The weak surface low and associated frontal boundary will persist
across the Southeast. Low-level flow, while generally southwesterly,
will be light enough to allow the Atlantic sea breeze to push inland
each afternoon. Meanwhile, a persistent upper ridge over the Desert
Southwest, Southern Plains, and ArkLaTex region will facilitate a
drier mid- to upper-level air mass, leading to a gradual reduction
in precipitation chances early next week.

Sunday: Scattered afternoon and evening showers and thunderstorms
will remain possible as the upper trough axis shifts offshore.
Temperatures will remain in the lower to mid 90s, with heat index
values around 105F.

Monday and Tuesday: Precipitation chances will decrease as the
sprawling ridge strengthens across the southern Plains and ArkLaTex
region, resulting in a drier mid to upper level atmosphere. On
Monday, PoPs will range from 1020% across Southeast Georgia to
3050% across Northeast Florida. By Tuesday, isolated to widely
scattered showers and thunderstorms are expected area wide,
primarily during the afternoon and evening.

Wednesday: Another upper-level trough will move into the eastern
CONUS, providing an increase in moisture and forcing. This will
support scattered afternoon and evening showers and thunderstorms,
with rain chances increasing to 3545%. Storms will be driven
primarily by diurnal instability and sea breeze interactions. While
widespread severe weather is not expected, isolated strong storms
will remain possible, with gusty winds, frequent lightning, and
locally heavy rainfall as the primary hazards.

Highs through the long term period will generally be in the lower to
mid 90s, with afternoon heat index values around 105F. Overnight
lows will remain in the mid 70s. Overall, hot and humid conditions
will continue, although heat impacts should be less extreme than
during the current heat streak.

&&

.AVIATION /00Z FRIDAY THROUGH 00Z SATURDAY/...
Shower and thunderstorm coverage will continue to decrease as VCSH
or -RA noted in TAFs. Kept MVFR fog prevailing at VQQ and GNV as
lighter winds develop, around 5 knots to near calm after 04Z.
Southwest winds return late Friday morning, with diurnal heating
bringing periods of showers and storms after 17Z for most TAF sites.
Kept any mention off SSI for now as confidence remains low for any
activity.

&&

.MARINE...


Weak high pressure to the west over the northern Gulf waters will
remain through the weekend into early next week and continue a west
to southwesterly flow over the waters. The Atlantic seabreeze will
develop each afternoon and move slowly inland, shifting winds to
south southeasterly and then southerly overnight as wind speeds
approach caution levels in the early evening and diminishing late
evening. A couple of cold front will move into the southeast states
and stall north of the area waters through early next week.
Scattered showers and thunderstorms will develop and impact the near
shore waters adjacent to northeast Florida this afternoon int early
evening. Coverage of thunderstorms will increase in the afternoon
and early evening hours over the local waters on Friday and
Saturday. Coverage of afternoon and evening thunderstorms will
decrease Sunday into Monday with more isolated or widely scattered
thunderstorms.

Rip Currents: Offshore winds will prevail throughout the morning
hours, along with low surf heights, during the next several days.
With the outgoing tide occurring later in the afternoon, the overall
risk will be low today and low to low end moderate this weekend as
an afternoon seabreeze brings light south to southeast winds to the
beaches.

&&

.FIRE WEATHER...
- Patchy high dispersions over SE GA this weekend through Monday

The frontal boundary across Georgia will sustain daily afternoon and
evening thunderstorm activity, with the highest coverage anticipated
Friday and Saturday. Potential exists for strong to locally severe
storms, capable of producing gusty, erratic winds, frequent
lightning, and locally heavy rainfall. Outside of these storms, no
significant fire-weather concerns are expected.

Fog Potential: Fog formation is unlikely, and any erratic wind
patterns will be isolated to thunderstorm activity.

&&

.CLIMATE...
Near record high temperatures are possible at some of our designated
climate sites during the next few days:

Thursday, August 20th:
KJAX: 101/1900
KGNV: 99/1900
KAMG: 104/1995
KCRG: 98/2016

Friday, August 21st:
KJAX: 101/1900
KGNV: 99/1983
KAMG: 100/1980
KCRG: 99/2016

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  74  97  72  93 /  10  60  50  50
SSI  77  94  77  92 /  10  40  30  60
JAX  75  95  74  92 /  10  40  20  70
SGJ  75  94  75  92 /  10  40  20  60
GNV  73  93  73  90 /  20  60  30  70
OCF  73  93  74  91 /  20  50  40  50

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Heat Advisory from 11 AM to 7 PM EDT Friday for FLZ038-125-132-
     137-138-232-233-237-325-333-433-533-633.
GA...None.
MARINE...None.

&&

$$