429
FXUS62 KJAX 021819
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
219 PM EDT Tue Jul 2 2024

...New AVIATION...

.AVIATION...
(18Z TAFS)
Issued at 219 PM EDT Tue Jul 2 2024

Showers and thunderstorms will continue to develop near the SSI
terminal through around 22Z. Elsewhere, convection will shift
inland across northeast and north central FL as the afternoon
progresses, with impacts expected at JAX, VQQ and GNV after 20Z
and possibly extending past sunset. Periods of IFR visibilities
will be possible at these terminals during heavier downpours,
along with brief wind gusts up to 30 knots. Thunderstorms should
shift inland from CRG and SGJ, but vicinity coverage may continue
through around sunset. MVFR visibilities are expected to develop
towards midnight at VQQ after convection winds down. MVFR
visibilities will be possible at GNV towards sunrise, but
confidence remains too low to indicate in the TAF at this time.
VFR conditions should otherwise prevail overnight at the regional
terminals. Outside of thunderstorm activity, easterly winds around
10 knots will prevail at the regional terminals through around
sunset. Speeds will diminish after sunset and will then increase
to 5-10 knots after sunrise on Wednesday.

&&

.UPDATE...
Issued at 1235 PM EDT Tue Jul 2 2024

Early afternoon surface analysis depicts a stalled and weakening
frontal boundary positioned across the Deep South. Meanwhile, high
pressure (1027 millibars) centered over the eastern Great Lakes
extends southward down the spine of the Appalachian mountains.
Aloft..."Heat Wave" ridging continues to build eastward from the
lower Mississippi and Tennessee Valleys towards the southeastern
seaboard as troughing departs the New England and Mid-Atlantic
coasts. Latest GOES-East derived Total Precipitable Water imagery
indicates that deep moisture remains in place throughout our
region, with PWAT values mostly in the 1.9 - 2.1 inch range, while
a much drier air mass exists to the north of the frontal boundary
across the Carolinas and northeastern GA. Scattered and slow
moving convection developed late this morning just south of the
stalled front across inland portions of southeast GA, with widely
scattered showers and thunderstorms also developing along the
Atlantic sea breeze boundary that is positioned along the
northeast FL coast. Thick, multi-layered cloud cover was located
across inland southeast GA for locations north of Waycross, which
was keeping temperatures in the 75-80 degree range, while
temperatures elsewhere outside of ongoing convection were
generally in the 85-90 degree range as of 16Z.

The presence of the stalled frontal boundary, differential heating
due to cloud cover north of the Okefenokee Swamp, and mesoscale
boundary collisions in a deeply moist air mass should allow for
convective coverage to increase across southeast GA through the
mid to late afternoon hours. Slow movement of convection may
result in localized flooding, especially where heavy downpours
train over urban areas such as Brunswick and Waycross, or over
normally flood prone locations. The Weather Prediction Center has
placed all of southeast GA and most of northeast FL within a
"Marginal" risk of Excessive Rainfall today (Level 1 of 4) for
this isolated flooding probabilities. Further south, plenty of
insolation this morning has destabilized the atmosphere, setting
the stage for scattered to numerous showers and thunderstorms this
afternoon and evening.

High pressure wedging down the southeastern seaboard will
increase low level easterly flow somewhat later this afternoon,
providing an inland push to the Atlantic sea breeze boundary. The
Gulf coast sea breeze will also push inland towards Interstate 75
towards sunset, setting up a collision of these sea breezes that
will result in increasing chances for convection, mainly for
locations west of the I-95 corridor. Storms will pulse in an
environment that features ML CAPE values of 1,500 - 2,500 j/kg for
locations along and south of I-10, with stronger storms this
afternoon and evening being capable of producing downburst winds
of 40-50 mph, frequent lightning strikes, and localized flooding
due to slow movement of thunderstorms. Highs this afternoon will
remain in the mid to upper 80s for locations north of Waycross,
with upper 80s and lower 90s elsewhere, except mid 90s for
portions of north central FL. Peak heat index values should remain
just below Heat Advisory criteria in northeast and north central
FL, with maximums generally in the 103-107 range.

Convection may be slow to wind down for locations west of the U.S.
Highway 301 corridor this evening as mesoscale boundary collisions
continue. Also, light onshore winds could develop isolated
convection at coastal locations during the overnight and predawn
hours on Wednesday. Low stratus ceilings are expected to develop
towards sunrise across inland southeast GA due to the presence of
the weakening frontal boundary. Lows tonight will fall to the low
and mid 70s at inland locations, with coastal lows in the upper
70s to around 80.

&&

.MARINE...
Issued at 1235 PM EDT Tue Jul 2 2024

A frontal boundary will remain stalled over the Georgia waters
through Wednesday. Prevailing winds will shift to easterly this
afternoon as high pressure building over the Mid-Atlantic states
wedges down the southeastern seaboard. Showers and thunderstorms
will increase in coverage across our local waters along and south
of this stalled frontal boundary through Wednesday. The frontal
boundary will gradually dissipate over the Georgia waters by
Thursday, with prevailing onshore winds continuing as high
pressure weakens off the eastern seaboard. Coverage of showers and
thunderstorms are expected to decrease across our local waters
late this week through Saturday, with prevailing winds then
shifting to southwesterly during the weekend ahead of the next
weakening frontal boundary that will be entering the southeastern
states. Seas of 2 to 4 feet will prevail both near shore and
offshore during the next several days.

Rip Currents: Onshore winds will become breezy this afternoon at
area beaches and will combine with a lingering east-southeasterly
ocean swell to create a low-end moderate rip current risk. This
moderate risk is expected to continue at all area beaches through
Independence Day.

&&

.FIRE WEATHER...
Issued at 1235 PM EDT Tue Jul 2 2024

Light and generally easterly transport winds will continue through
Wednesday, with scattered to numerous afternoon and evening
showers and thunderstorms and more extensive cloud cover keeping
daytime dispersion values in the poor to fair range throughout our
region. Mixing heights will begin to rise on Thursday, but
generally light transport wind speeds will keep daytime dispersion
values in the fair range at most locations during the afternoon
hours.

&&

.HYDROLOGY...
Issued at 400 AM EDT Mon Jul 1 2024

High moisture (PWATs ~2.3 inches) over the region will lead to
heavy downpours from convection especially along and ahead of an
approaching frontal boundary/trough from the north. WPC has placed
SE GA and small area of northeast FL in a marginal risk of
excessive rainfall today. Localized areas could see rain amounts
of 3 inches in a short period of time.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  74  91  74  93 /  60  70  30  60
SSI  79  89  79  90 /  50  50  30  40
JAX  75  92  75  92 /  30  70  20  70
SGJ  77  91  78  91 /  40  40  20  60
GNV  73  93  75  92 /  50  80  40  70
OCF  74  92  75  93 /  50  70  40  60

&&

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

$$