402
FXUS62 KJAX 230811
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
411 AM EDT Sun Jun 23 2024

...TYPICAL SUMMERTIME WEATHER PATTERN TAKES SHAPE THIS WEEK...
...HEAT INDEX VALUES APPROACH ADVISORY LEVELS EARLY THIS WEEK...
...MODERATE RIP CURRENT RISK CONTINUES TODAY AT AREA BEACHES...

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

.SYNOPSIS...
Issued at 411 AM EDT Sun Jun 23 2024

Early morning surface analysis depicts a lingering trough over
coastal GA and SC, with weak high pressure (1017 millibars)
otherwise centered over the lower Mississippi Valley.
Aloft...deep-layered "Heat Wave" ridging has retrograded westward
to a position over Texas and the lower Mississippi Valley, with
troughing in place along the southeastern seaboard and the western
Atlantic. Meanwhile, a potent shortwave trough was progressing
across the Great Lakes region. Latest GOES-East derived Total
Precipitable Water imagery nicely displays the weak trough axis
that was in place locally, with PWATS for locations west of the
U.S. Highway 301 corridor generally in the 1.6- 1.8 inch range,
while a more humid air mass prevails east of U.S.-301, where PWATS
were above 2 inches. The trough axis continues to fire convection
over the offshore Atlantic waters north of St. Augustine and for
the near shore waters from St. Augustine southward, with showers
developing along the trough axis across portions of north central
FL. Multi-layered cloudiness prevails across our area, especially
for locations along and east of U.S.-301 that fall within the more
humid air mass. Temperatures at 08Z were in the 70s inland,
ranging to around 80 at coastal locations. Dewpoints remain in the
70s region-wide.

&&

.NEAR TERM...
(through Tonight)
Issued at 411 AM EDT Sun Jun 23 2024

Low level troughing in place over the Savannah River Valley will
progress slowly northeastward today, exiting the SC coast this
evening. West-northwesterly mid-level flow on the western
periphery of this trough will attempt to advect the drier air mass
currently in place for locations west of U.S. Highway 301 eastward
towards the I-95 corridor this afternoon. However, a weak pressure
pattern prevailing across our region should allow for the Gulf and
Atlantic sea breezes to develop by early afternoon, with PWAT
values close enough to climatology to develop numerous afternoon
and early evening showers and thunderstorms for northeast and
north central FL, mainly due to mesoscale boundary collisions as
convective trigger temperatures in the mid 90s are realized.
Coverage will be scattered along the Gulf coast sea breeze in the
Suwannee Valley and also along the Atlantic sea breeze for coastal
southeast GA, with only isolated to widely scattered coverage for
inland southeast GA as convective outflows pushing north and
northwestward potentially overcome the below climatology PWAT
values. The drier air mass advecting into our region will allow
for downdraft CAPE values to climb to the 1,000-1,500 j/g range,
which may allow for a few storms to become strong as mesoscale
boundaries collide as storms pulse, with stronger activity capable
of producing downburst winds of 40-50 mph, frequent lightning
strikes, and heavy downpours. West-northwest steering flow will
tend to focus mesoscale boundary collisions near the U.S. Highway
17 corridor late this afternoon, with activity likely migrating
towards the I-95 corridor towards sunset.

Seasonably hot temperatures will build over our region today, with
highs for inland southeast GA and the Suwannee Valley soaring to
the upper 90s, while locations elsewhere climb to the low and mid
90s. Dewpoints within the drier air mass are likely to crash
through the 60s across inland southeast GA this afternoon, keeping
maximum heat index values around 105. Values could approach Heat
Advisory criteria in the Suwannee Valley this afternoon, with a
general range of 103-107 degrees expected across our area. We will
monitor forecast trends for counties such as Suwannee, Hamilton,
Echols, and Gilchrist, which have the higher chances for touching
the 108 degree threshold for a Heat Advisory.

Convective outflows could keep activity percolating across
northeast and north central FL through around midnight, with
debris cloudiness potentially lingering overnight and developing
west-southwesterly low level flow potentially developing isolated
to widely scattered convection along the Nature Coast during the
predawn hours on Monday that could sneak into western portions of
Marion, southern portions of Gilchrist, and southwestern Alachua
Counties before sunrise. A warm and humid air mass will keep lows
generally in the mid 70s inland and the upper 70s to around 80 at
coastal locations.

&&

.SHORT TERM...
(Monday through Tuesday night)
Issued at 411 AM EDT Sun Jun 23 2024

Predominately S/SW flow will allow for seasonably hot temperatures
and decent moisture Monday and Tuesday, with highs soaring into
the mid to upper 90s, with a few areas in inland SE GA seeing
highs of 100 on Tuesday. Heat indices both afternoons will top out
in the 100-106 range, just below Heat Advisory criteria as of
now. Diurnal showers and thunderstorms will develop as the Gulf
sea breeze dominates with the southwesterly flow, the highest
precip potential will be over NE FL.

&&

.LONG TERM...
(Wednesday through Saturday)
Issued at 411 AM EDT Sun Jun 23 2024

A more typical summer-time like pattern will be in place, with
both the Gulf and Atlantic sea breezes moving inland and
interacting each day, sparking scattered to numerous shower and
thunderstorm development. Temperatures will remain above normal
through the week, with highs reaching the lower to upper 90s with
lows in the 70s.

&&

.AVIATION...
(06Z TAFS)
Issued at 204 AM EDT Sun Jun 23 2024

VFR conditions will prevail at the regional terminals through at
least 18Z. Showers and thunderstorms will begin developing along
the inland moving Gulf and Atlantic sea breeze boundaries on
Sunday afternoon, with activity merging near and east of the U.S.
Highway 301 corridor during the late afternoon and early evening
hours. We have included a PROB30 group at each terminal for
briefly gusty winds and MVFR conditions during heavier downpours
for the afternoon and early evening hours on Sunday. VFR
conditions should then prevail by 04Z Monday. Southerly winds
sustained at 5-10 knots overnight will shift to southwesterly
after sunrise, with speeds increasing to around 10 knots by 16Z.
The Atlantic and Gulf coast sea breezes will move inland on Sunday
afternoon, resulting in surface winds shifting to southeasterly
and increasing to 10-15 knots at the SSI and SGJ coastal terminals
towards 19Z, with these southeasterly winds reaching the CRG and
JAX terminals as convection begins to increase in coverage after
20Z. After convection wanes on Sunday evening, expect southerly
surface winds to remain sustained at 5-10 knots at the inland
terminals and 10-15 knots at the coastal terminals.

&&

.MARINE...
Issued at 411 AM EDT Sun Jun 23 2024

Weak troughing will linger over our area today, with prevailing
southwesterly winds this morning shifting to southeasterly over
the near shore waters this afternoon as the Atlantic sea breeze
moves inland. Showers and thunderstorms will be more numerous
during the morning hours today offshore, with evening activity
more likely for the near shore waters. Seas of 3-5 feet will
prevail both near shore and offshore through tonight. Winds will
shift to south-southwesterly and will surge to Caution levels of
15-20 knots throughout our local waters this evening outside of
ongoing thunderstorm activity. West-southwesterly winds will
prevail for the rest of the week as another trough settles over
the southeastern states, with scattered thunderstorm chances
prevailing each afternoon and evening as activity moves eastward
across our local waters. Speeds will generally remain below
Caution levels outside of thunderstorm activity, with seas of 2-4
feet prevailing throughout our local waters from Monday through
Friday.

Rip Currents: Developing onshore winds this afternoon will combine
with an easterly ocean swell to create a moderate rip current risk
at all area beaches. The easterly swell will begin to fade on
Monday, dropping the risk to low for the southeast GA beaches,
while onshore winds during the afternoon keep a lower end moderate
risk at the northeast FL beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  97  75  96  75 /  30  10  30  20
SSI  92  78  93  79 /  40  20  30  30
JAX  96  75  96  75 /  60  30  50  20
SGJ  93  77  94  76 /  50  40  60  20
GNV  95  75  95  73 /  70  40  70  10
OCF  93  74  93  75 /  60  40  70  20

&&

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

$$