Jasper, Florida Weather Forecast Discussion

799
FXUS62 KJAX 161542
AFDJAX
Area Forecast Discussion
National Weather Service Jacksonville FL
1142 AM EDT Tue Sep 16 2025
...MINOR TIDAL FLOODING CONTINUES WITHIN THE ST. JOHNS BASIN...
...INLAND HIGHS RISE TO SEASONABLY WARM LEVELS...
...ANOTHER WEEKEND NOR`EASTER EXPECTED TO TAKE SHAPE...
For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf
.UPDATE...
Issued at 1142 AM EDT Tue Sep 16 2025
Late morning surface analysis depicts low pressure (1008
millibars) meandering near Cape Hatteras, while high pressure
(1022 millibars) stretches across the southeastern states to the
south of this feature. Aloft...cutoff troughing continues to swirl
across the Carolinas, while ridges were located over the
southeastern Bahamas and also from the southern Plains
northeastward across the Great Lakes region. Latest GOES-East
derived Total Precipitable Water imagery indicates that an
unseasonably dry air mass prevails across our region, with PWAT
values around 1 inch throughout southeast GA and northeast FL,
ranging to around 1.3 inches for north central FL. Brisk west-
southwesterly flow prevails above 450 millibars (around 22,000
feet) per the morning sounding at Jacksonville, with this brisk
flow transporting a veil of cirrus over locations south of the
Interstate 10 corridor. Meanwhile, a flat cumulus field was
developing over most of northeast FL and the Suwannee Valley. Fair
skies prevail across southeast GA, and temperatures area wide were
climbing to the upper 70s and lower 80s. Dewpoints were generally
in the 60s area-wide as of 15Z.
Cutoff troughing will nudge northward this afternoon and tonight,
keeping brisk southwesterly flow aloft in place across our area.
Pockets of mostly thin cirrus cloud cover will continue to move
across the skies of northeast and especially north central FL this
afternoon. Meanwhile, a dry air mass in place across our area will
result in a flat cumulus field expanding across the rest of our
region this afternoon. Breezy northeasterly winds will keep
coastal highs in the mid 80s today, while inland highs climb to
the upper 80s to around 90. Heat index values will be held in
check as dewpoints fall into the 50s across inland southeast GA
and the 60s elsewhere.
Cirrus cloud cover will thicken somewhat while increasing in
coverage across our area tonight, especially for locations south
of Waycross. This cloud cover may thin out as it progresses
eastward during the predawn or early morning hours. Some patches
of fog could develop across inland southeast GA and the Suwannee
Valley as this cloud cover departs, but confidence was too low to
include in the forecast at this time. Given the dry air mass in
place, we trended lows a few degrees below model blends, yielding
minimums in the 60-65 range inland, with upper 60s and lower 70s
for north central and coastal locations.
&&
.SHORT TERM...
(Wednesday through Thursday night)
Issued at 1246 AM EDT Tue Sep 16 2025
Wednesday will remain a dry one as the upper low/trough to our
northeast will take its time weakening and lifting off to the
northeast through Thursday. Though some higher PWATs near 1.5
inches try to sneak into the area as a frontal boundary well to
the south wobbles north, still expecting it to be too dry for any
rain chances, especially with weak subsidence still in place. The
weakening/departing surface and upper low will also weaken the
pressure gradient a bit on Thursday, and therefore onshore winds
are expected to weaken to around the 5-10mph range except with a
slightly higher sea breeze influence along the coast. This may
also taper coastal flooding along the St. Johns River a bit and
allow some of the trapped water to start to drain - will certainly
monitor trends over the next 12-24 hours, though for the time
being Coastal Flood Advisory remains in effect through Wednesday
Evening for the St. Johns River Basin at this time. Weaker onshore
flow will result in very warm high temps Wednesday as well, with
upper 80s to near 90 common inland and mid 80s by the coast. Lows
Thursday Morning range from the mid 60s inland to the low 70s
closer to the coast and St. Johns River with just some isolated
mid/high clouds.
Layer moisture makes slightly more of a jump Thursday as the
aforementioned front to our south nudges further north, mainly
having impacts for south and eastern parts of northeast FL. Still
will be enough of lingering dry air and subsidence to limit any
rain chances to areas south of a line from about Gainesville to
Saint Augustine and especially closer to the coast, with
decreasing cloud cover the further north and west you go into
interior NE FL and SE GA. A slight turn in the flow will also be
expected as the front nudges north, with more of a due easterly to
east/southeast flow around 5-10mph inland and around 10-15mph near
the coast. Very warm temps will continue inland with highs around
or just above 90 common, closer to the mid to upper 80s closer to
the coast. A few showers will likely continue Thursday Night,
mainly along the coast south of Saint Augustine. Elsewhere, a
decrease in clouds with lows ranging from the mid to upper 60s
inland to the low 70s south and east.
&&
.LONG TERM...
(Friday through Monday)
Issued at 1246 AM EDT Tue Sep 16 2025
The aforementioned frontal boundary does not get much further than
central FL around Friday before another ridge of high pressure
builds across the southeast US towards north FL. Though it does
not look as strong as the previous event, still looks like strong
enough ridging combines with developing broad troughing over the
western Atlantic to induce a northeasterly wind event. Breezy
flow and increasing low level moisture will return chances for
showers and some isolated thunderstorms for most of the area this
weekend and into early next week, especially closer to the coast.
This will also support deteriorating surf zone conditions with the
potential for high rip current risk, small craft advisory
conditions, and the continuation and expansion of tidal flooding
to coastal areas as well. Temperatures start the period generally
above normal, though trending closer to normal throughout the
weekend and into early next week.
&&
.AVIATION...
(12Z TAFS)
Issued at 735 AM EDT Tue Sep 16 2025
VFR conditions will prevail at the regional terminals through at
least 05Z Wednesday. IFR conditions are expected to develop at
VQQ after 05Z, with MVFR visibilities possible at GNV after 09Z.
North-northwesterly surface winds of 5-10 knots at the SSI and SGJ
coastal terminals early this morning will shift to northeasterly
by 15Z, with speeds increasing to 10-15 knots by 16Z. Light
northerly surface winds elsewhere at the inland terminals will
shift to east-northeasterly by 16Z, with speeds increasing to
around 10 knots. Surface winds will then shift to east-
southeasterly towards sunset, with speeds gradually diminishing
this evening.
&&
.MARINE...
Issued at 1142 AM EDT Tue Sep 16 2025
Low pressure located near Cape Hatteras will meander northward
towards the Chesapeake Bay tonight and Wednesday before weakening
off the Mid-Atlantic coast later this week. Weak high pressure
will remain situated over our region to the south of this coastal
low through Thursday. Seas of 3 to 5 feet will prevail across our
local waters through tonight, diminishing to 2 to 4 feet from
Wednesday through Thursday night. Strong high pressure will then
build southeastward from Hudson Bay, Canada late this week, with
this feature shifting over New England by Saturday as it wedges
down the southeastern seaboard. Coastal troughing will sharpen
over our near shore waters this weekend, resulting in
strengthening onshore winds, building seas, and an increasing
coverage of showers and thunderstorms across our local waters.
Small Craft Advisory conditions are possible late this weekend and
early next week.
Rip Currents: Breaker heights of 4-5 feet at the northeast FL
beaches and 2-4 feet at the southeast GA beaches will combine
with a long period northeasterly ocean swell to create a higher
end moderate rip current risk at all area beaches today. Breaker
heights will subside to the 2-4 foot range at the northeast FL
beaches on Wednesday and Thursday, allowing for a lower end
moderate risk.
&&
.FIRE WEATHER...
Issued at 1142 AM EDT Tue Sep 16 2025
An unseasonably dry air mass will continue at inland locations
through Thursday, with minimum relative humidity values falling to
the 30-35 percent range for inland southeast GA and the Suwannee
Valley this afternoon, with minimum values of 35-40 percent then
expected on Wednesday and Thursday. North-northeasterly surface
and transport winds will become breezy at coastal locations this
afternoon. Elevated mixing heights at inland locations will
create generally good daytime dispersion values, while fair values
are forecast elsewhere. Lighter easterly surface and transport
winds are expected on Wednesday for northeast and north central
FL, with light southwest to westerly winds across inland southeast
GA. Elevated mixing heights should create fair daytime dispersion
values for most of inland southeast GA, with pockets of poor
values possible. Fair to good daytime dispersion values are
expected elsewhere. Light southeasterly surface and transport
winds are then forecast for inland southeast GA and the northern
Suwannee Valley on Thursday, where elevated mixing heights should
allow for fair to good daytime dispersion values. Easterly surface
and transport winds will prevail elsewhere, with fair to good
daytime dispersion values remaining in the forecast.
&&
.HYDROLOGY...
Issued at 1142 AM EDT Tue Sep 16 2025
As northeasterly winds gradually weaken across the Atlantic
Coastal waters, this has allowed the intracoastal waterway to fall
below minor flood stages along the northeast FL Atlantic coast,
and the Coastal Flood Advisory has been discontinued for coastal
Flagler and St. Johns Counties. Lingering weak onshore flow has
still not allowed the St. Johns River Basin to drain out, and
minor, nuisance-type flooding will continue around times of high
tide through Saturday, with water levels rising to 1 - 1.5 ft
above Mean Higher High Water (MHHW) around times of high tide.
Tidal flooding is then expected to expand to the Atlantic Coastal
areas this weekend through early next week due to a surge of
onshore winds as another weekend local Nor`Easter takes shape.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG  90  62  90  65 /   0   0   0   0
SSI  83  68  85  71 /   0   0   0   0
JAX  88  65  90  69 /   0   0   0   0
SGJ  85  69  87  71 /   0   0   0  10
GNV  91  64  91  67 /   0   0   0   0
OCF  90  66  90  69 /   0   0  10   0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 8 PM EDT Wednesday for FLZ125-132-
     137-325-633.
GA...None.
AM...None.
&&
$$

NWS JAX Office Area Forecast Discussion