Fleming Island, Florida Weather Forecast Discussion

246
FXUS62 KJAX 201512
AFDJAX
Area Forecast Discussion
National Weather Service Jacksonville FL
1112 AM EDT Sat Sep 20 2025
...New UPDATE, MARINE, FIRE WEATHER...
.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
- High Rip Current Risk at the Northeast FL Beaches
- Inland Fog Potential Late Tonight and Early Sunday Morning
- Minor Tidal Flooding - St. Johns River Basin Early Next Week
&&
.UPDATE...
Issued at 1112 AM EDT Sat Sep 20 2025
Late morning surface analysis depicts strengthening high pressure
(1031 millibars) building southeastward from Quebec towards the
eastern Great Lakes and New England. Meanwhile, coastal troughing
was sharpening over the offshore waters adjacent to northeast FL,
with this feature generating scattered showers beyond 25 nautical
miles offshore of St. Augustine. Aloft...zonal flow prevails
across the Deep South. Meanwhile, cutoff troughing over the Upper
Midwest was directing a shortwave trough east-southeastward from
the Southern Plains towards the Ozarks. Latest GOES-East derived
Total Precipitable Water imagery indicates that the persistent,
unseasonably dry air mass that prevailed across most of our area
during the past week has gradually moistened, with PWATS generally
between 1.25 - 1.5 inches throughout our region, which remains
slightly below late September climatology. Our local pressure
gradient is in the process of gradually tightening, with breezy
onshore winds at coastal locations helping to develop a healthy
cumulus field for locations along and east of U.S. Highway 301.
Temperatures at 15Z were climbing through the low and middle 80s
at most locations, with the moistening air mass now yielding
dewpoints mainly in the low to mid 70s across our area.
Our local pressure gradient will continue to gradually tighten
this weekend as strong high pressure builds over New England, with
this feature wedging down the southeastern seaboard and combining
with a sharpening coastal trough offshore to create breezy winds
along the I-95 corridor this afternoon. This tightening gradient
will shove the Atlantic sea breeze boundary well inland this
afternoon, with isolated, low-topped convection possible for
inland locations south of I-10 and along/west of the U.S. Highway
301 corridor through sunset. An overall subsident environment
persisting over our region should keep any shower activity that
develops brief in duration for any one inland location, and
dewpoints will fall back to the 60s for locations west of I-95.
Plenty of sunshine will otherwise boost highs to the lower 90s
inland, with maximum heat index values remaining below 100. Breezy
onshore winds will keep coastal highs mostly in the mid or upper
80s.
High pressure wedging down the southeastern seaboard will advect a
pocket of drier air southwestward across our area overnight, with
model soundings indicating that PWATs will fall below 1.25 inches.
This drier air should limit any convergent shower activity to the
Atlantic waters, with winds west of U.S.-301 decoupling overnight.
Some patchy fog could develop for inland portions of southeast GA
during the predawn hours on Sunday, mainly for locations west of
Waycross. Subsidence and fair skies inland tonight will allow lows
to fall to the 60-65 range, while an onshore breeze keeps coastal
lows generally in the mid 70s.
&&
.SHORT TERM...
(Sunday through Monday night)
Issued at 204 AM EDT Sat Sep 20 2025
High pressure ridging will extend SSW from the New England coast
into the Carolinas. Dry air will extend into the region from the
ridging and the associated increased subsidence will help suppress
pops over the area with only silent pops now forecast due to below
average Precipitable Water levels 1.1-1.4 inches (average PW values
are around 1.6 inches for mid/late September). A pinched gradient
will exist over the coast/waters between the high to the NNE and
weak coastal troughing well east of the waters and will support
breezy winds at the coast 15-20 mph with gusts to 25-30 mph slightly
less inland 10-15 mph. Partly cloudy skies mainly from scattered
Atlantic stratocumulus clouds moving onshore and bubbling inland
under high level cirrus clouds and should allow highs to reach the
low 90s inland near I-75 and west of Waycross while the cooler
onshore flow will limit highs into the mid 80s at the beaches and
the upper 80s along I-95.
Sunday night, high level clouds will increase with increasing
coastal showers towards dawn. A gradient of lows will result due
to drier air inland with mid 60s over inland SE GA, the upper 60s
along I-10 inland to the suwannee Valley, with low 70s along the
coast and St Johns river and north central FL as NE onshore winds
continue 10-15 mph at the coast diminishing to around 5 mph inland.
Monday, frontal boundary to the south will begin to lift northward
along the FL peninsula/eastern Gulf as the high extending from the
NNE weakens and retreats in to the north Atlantic waters. Mostly
cloudy skies due to increasing high/mid level clouds north of the
frontal boundary will prevail Monday as scattered coastal showers
move onshore in the morning hours with isolated to scattered T`storm
coverage by the afternoon, especially from the St Johns river east
to the coast. Onshore winds will be lighter due to a weaker gradient
10-15 mph along the coast becoming 5-10 mph inland. Highs will be
a little less Monday due to more clouds with upper 80s inland and
the mid 80s coast.
Monday night, skies will become partly cloudy overnight as high
level clouds decrease with lows ranging from the mid 60s across
inland SE GA and the low 70s along the coast.
&&
.LONG TERM...
(Tuesday through Friday)
Issued at 204 AM EDT Sat Sep 20 2025
Tuesday, a lifting shortwave from the eastern Gulf will shift NE
across the area ahead of broad troughing progressing east across
the Appalachian mountains. High pressure will reform at the surface
more to the ENE through Wednesday with light easterly winds and
scattered coastal showers moving onshore in the morning hours
with isolated afternoon T`storms over coastal SE GA and inland
NE FL with slightly higher coverage over the St Johns river into
north central FL.
An upstream mid to upper level trough will deepen and swing to the
east Thursday into Friday, supporting a cold front moving across the
deep south Thursday and into our area by late Friday/early Saturday.
Timing difference between global models remain at this stage and for
now have 40-50 percent pops across the entire area late this week as
the front moves in.
Temperatures will warm from near normal Tuesday to above normal
Wednesday into Friday with low 90s near the coast to end the week.
&&
.AVIATION...
(12Z TAFS)
Issued at 800 AM EDT Sat Sep 20 2025
VFR conditions will prevail at the regional terminals through at
least 05Z Sunday. Broken ceilings of 3,500 - 4,500 feet will
likely progress westward across the terminals throughout the
afternoon hours, with clearing from east to west as the Atlantic
sea breeze boundary shifts inland. An isolated, brief shower
cannot be ruled out at SGJ after 16Z, but confidence was too low
to indicate vicinity coverage at this time. IFR to LIFR conditions
are expected to develop at VQQ after 05Z. Northwesterly surface
winds sustained around 5 knots early this morning will shift to
northeasterly towards 15Z, with speeds increasing to 10-15 knots
early this afternoon. Light northerly surface winds will develop
elsewhere after 13Z, followed by winds shifting to northeasterly
while increasing to around 10 knots early this afternoon.
Northeasterly surface winds will remain sustained at 5-10 knots
overnight at the SSI and SGJ terminals, and winds will shift
slightly to north-northeasterly towards sunrise on Sunday. Winds
at the inland terminals will diminish after sunset.
&&
.MARINE...
Issued at 1112 AM EDT Sat Sep 20 2025
High pressure building over New England will wedge down the
southeastern seaboard this afternoon and tonight, sharpening a
coastal trough situated offshore. Northeasterly winds will
gradually strengthen to Caution levels of 15-20 knots on Sunday,
with scattered showers and thunderstorms developing, mainly over
the offshore waters and the near shore waters adjacent to
northeast Florida. Seas of 2-4 feet will generally prevail both
near shore and offshore through tonight, followed by a slight
increase to the 3-5 foot range from Sunday through Monday night.
High pressure will then gradually weaken as it shifts southward
down the U.S. eastern seaboard early next week, allowing winds and
seas to diminish.
Rip Currents: Strengthening northeasterly winds will build
breaker heights to the 3-4 foot range this afternoon at the
northeast FL beaches, creating a high rip current risk. Breakers
of 2-3 feet will likely yield a higher end moderate risk at the
southeast GA beaches. Breakers on Sunday and Monday will build to
the 4-5 foot range at the northeast FL beaches, maintaining a high
risk, while 2-3 foot breakers at the southeast GA beaches likely
will maintain a higher end moderate risk.
&&
.FIRE WEATHER...
Issued at 1112 AM EDT Sat Sep 20 2025
Northeasterly surface and transport winds will gradually
strengthen this afternoon, with breezy surface speeds expected at
coastal locations. These strengthening winds will combine with
elevated mixing heights to create good daytime dispersion values,
except fair values for coastal locations north of St. Augustine.
Breezy northeasterly surface and transport winds will expand to
inland locations by early Sunday afternoon, with continued
elevated mixing heights creating high daytime dispersion values
for inland locations west of the U.S. Highway 301 corridor, while
good values are forecast elsewhere. Northeasterly surface and
transport winds will then weaken somewhat on Monday, with breezy
surface speeds continuing at coastal locations. Good daytime
dispersion values will prevail inland, while fair values prevail
for locations along and east of I-95.
&&
.HYDROLOGY...
Issued at 204 AM EDT Sat Sep 20 2025
Localized `action` stage tidal flooding is expected around high
tides today along the local coast and within the St. Johns river
basin. Latest model guidance (ETSS and PETSS) is trending lower
with high tide crests today given a weaker local nor`easter event
compared to events earlier in the month, and will continue to hold
off on a Coastal Flood Advisory at this time for today. Model
guidance continues to favor greater risk of tidal flooding in the
St. Johns River basin late Sunday through mid-week next week given
trapped tides/reverse flow event due to persistent easterly winds.
A coastal flood advisory may be needed for portions of the St.
Johns River basin late Sunday or by Monday to message minor tidal
flooding impacts early next week with inundation of 1-1.5 ft MHHW
datum around daily high tides.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG  90  64  89  65 /  10   0   0   0
SSI  85  70  84  73 /  10  10   0  10
JAX  89  67  88  70 /  10   0  10   0
SGJ  86  72  86  73 /  10  10  10  10
GNV  92  62  92  69 /  20   0   0   0
OCF  91  68  90  70 /  20  10  10   0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Monday evening for FLZ124-125-138-
     233-333.
GA...None.
AM...None.
&&
$$

NWS JAX Office Area Forecast Discussion