181
FXUS62 KJAX 301418
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
1018 AM EDT Tue Apr 30 2024

...New UPDATE...

.UPDATE...
Issued at 1010 AM EDT Tue Apr 30 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 basic forecast looks on track. Analysis shows mid level shortwave
trough just to our west and expected to track to the east through
the day. The observed sounding shows a large subsidence inversion
at about 7500 ft, but weaker than yesterday, and added low level
moisture. Forecast soundings shows the inversion breaking down
further this afternoon with sufficient cooling aloft associated
with the shortwave and added moisture with the east coast sea
breeze to produce isolated to scattered showers and potential
storms. Estimated MLCAPE still remains on the low end at about
500-1000 J/kg, potentially a bit higher along the sea breeze where
moisture is more maximized. The forecast POPs today look good
with only slight adjustments with some initial development along
the east coast over northeast FL this morning. While we don`t anticipate
severe storms, the bulk shear of about 30-35 kt could support a strong
storm in southeast GA, closer to some upper level forcing. The main
threat would be some small hail and strong wind gusts late afternoon
and early evening, with increasing probabilities from southeast
GA northwestward.

&&

.NEAR TERM...
Issued at 315 AM EDT Tue Apr 30 2024

A shortwave aloft will pass through the region today driving a
weakening frontal boundary through the SE US. Meanwhile, surface
high pressure off the GA/SC coast will shift further into the
Atlantic causing flow to shift to south-southwesterly. This will
allow for both Atlantic and Gulf sea breezes to shift inland this
afternoon and likely converge along US 17 in the evening.
Southerly flow combined with the passing shortwave will provide
enough moisture and instability for isolated showers and storms to
develop along the sea breezes mainly along their collision.
Scattered showers and storms will move across inland SE GA late
this afternoon into evening as the frontal boundary swings
through. Lingering low level moisture and calming winds will lead
to patchy fog developing for inland areas early Wednesday morning.
Highs today will be in the mid to upper 80s inland and low 80s
along the coast. Overnight lows will be in the 60s.

&&

.SHORT TERM...
(Wednesday through Thursday night)
Issued at 315 AM EDT Tue Apr 30 2024

A shortwave trough that will be traversing the Deep South on
Tuesday night will reach the Carolina coast on Wednesday morning,
resulting in deep-layer flow over our region shifting to
northwesterly. A weak surface reflection of this shortwave will
be left behind over our region, with slightly deeper moisture
(PWATS around 1.4 inches) pooling ahead of this feature, helping
to trigger mostly isolated convection along mesoscale boundaries
such as the Atlantic sea breeze and the St. Johns River breeze
during the late afternoon and early evening hours. Following the
dissipation of fog during the early morning hours, plenty of
sunshine from the mid-morning through mid-afternoon hours will
boost highs on Wednesday to the upper 80s to around 90 at inland
locations, while the afternoon sea breeze keeps coastal highs
generally in the mid 80s. Beneath fair skies, lows will only fall
to the 60s on both Wednesday night and Thursday night, with
patchy to areas of radiation fog expected to develop during the
predawn and early morning hours at inland locations.

A weak surface pressure pattern will prevail again locally on
Thursday, with ridging aloft building into our area in the wake of
Wednesday`s departing shortwave trough. Low level flow will shift
to easterly, with a drier and more subsident air mass advecting
over our area. Just enough moisture may remain around for isolated
convection to develop towards sunset where the Atlantic and Gulf
coast sea breezes collide towards sunset, generally for locations
in north central FL and the Suwannee Valley. The drier air mass
and plenty of sunshine will allow highs to soar to near 90 degrees
on Thursday, while highs top out in the low to mid 80s at coastal
locations, where prevailing onshore winds will become breezy
during the afternoon hours.

&&

.LONG TERM...
(Friday through Monday)
Issued at 315 AM EDT Tue Apr 30 2024

Ridging aloft over our region early on Friday will flatten in response
to a slowly evolving and digging trough that will encompass the Pacific
Northwest, the northern Rockies, and the upper Midwest. The flattening
of the ridge will allow for a more zonal flow pattern to develop, and
shortwave troughs embedded within this zonal flow will traverse our area,
mainly on Saturday and then again early next week. A dry air mass is
expected to linger throughout much of Friday across our area, with model
guidance generally keeping convection associated with the upstream
shortwave trough just west of our region, although some isolated convection
developing along mesoscale boundaries cannot be ruled out. Plenty of
sunshine from Friday morning through the mid-afternoon hours and the
lingering dry air mass will again boost highs to around 90 at most inland
locations, with the afternoon Atlantic sea breeze keeping coastal highs in
the low to mid 80s. Lows on Friday night will only fall to the 65-70 degree
range at most locations as convective debris clouds from upstream convection
filter overhead.

The aforementioned initial shortwave trough that is currently expected
to traverse our area on Saturday should bring at least widely scattered
convection to our area, especially during the afternoon and evening
hours. Weak flow aloft should preclude any severe weather threat, with
longer term models also suggesting that higher CAPE values will remain
west of our region. Forecast confidence then decreases late in the weekend
and early next week, as the longwave trough situated over the northern
tier of the nation potentially lifts into Canada, leaving behind a weak
frontal boundary over the southeastern states. Some subsidence in the wake
of the initial shortwave trough passage may result in less convective
coverage along mesoscale boundaries on Sunday, and then the 00Z operational
GFS/ECMWF guidance diverges on the timing of the next shortwave trough that
could impact our area early next week. Slightly above average temperatures
will continue overall this weekend and early next week, with active sea
breezes moving well inland as Atlantic surface ridging extends its axis
across north central FL.

&&

.AVIATION...
(12Z TAFS)
Issued at 606 AM EDT Tue Apr 30 2024

VFR conditions will prevail at the regional terminals through at
least 18Z. Isolated to widely scattered showers and thunderstorms
are expected to develop during the mid to late afternoon hours,
mainly along mesoscale boundaries such as the Gulf and Atlantic
sea breezes. Confidence in coverage remains too low to include
anything other than vicinity coverage at this time. Activity may
linger into the early evening hours at the Duval County terminals,
as the Gulf and Atlantic sea breezes collide near U.S. Highway 301
around sunset, with any activity that manages to develop moving
back towards the I-95 corridor. Fog may be more widespread during
the predawn and early morning hours on Wednesday at the inland
terminals, and confidence was high enough to include TEMPO LIFR
conditions after 07Z at VQQ, with prevailing MVFR conditions
expected at JAX, GNV, and CRG by 10Z Wednesday. Southerly surface
winds will increase to 5-10 knots after 13Z at the regional
terminals, with the Atlantic and Gulf sea breeze boundaries
pushing inland this afternoon, resulting in surface winds shifting
to southeasterly at the coastal terminals by 17Z and then
spreading inland, except at GNV, where surface winds will shift to
southwesterly around 10 knots by 20Z. Surface winds will then shift
to southeasterly this evening while gradually diminishing.

&&

.MARINE...
Issued at 315 AM EDT Tue Apr 30 2024

High pressure centered off the South Carolina coast will weaken
and shift eastward today as a weakening frontal boundary enters
the southeastern states. South-southeasterly winds prevail this
morning with a coastal surge in the afternoon as the Atlantic sea
breeze shifts inland. Isolated showers and thunderstorms may
develop over our local waters today into Wednesday as the
dissipating frontal boundary moves over our area. Another high
pressure center will then build over coastal New England late this
week, resulting in onshore winds redeveloping over our local
waters. A cold front is then expected to enter the southeast
states by Saturday night and Sunday, possibly bringing a chance of
showers and thunderstorms to our region by late in the upcoming
weekend.

Rip Currents: Moderate risk of rip currents continue through
Wednesday with the potential for a high risk of rip currents at NE
FL beaches on Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  85  63  88  63 /  30  30  10   0
SSI  80  67  84  67 /  10  10  10   0
JAX  85  65  88  65 /  20  20  20  10
SGJ  83  67  86  67 /  10  10  20  10
GNV  87  64  89  63 /  20  10  20   0
OCF  87  64  89  64 /  20  10  20   0

&&

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

$$