Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 271433
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
1033 AM EDT Wed Mar 27 2024

...New UPDATE...

.UPDATE...
Issued at 938 AM EDT Wed Mar 27 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

An occluded front extends from the NE Gulf of Mexico to Central
South Carolina with cold upstream from the FL Panhandle to eastern
TN. Ahead of both features southerly winds are prevailing with H8
southwesterly transport winds of 25 knots bringing in ample Gulf
moisture into the region. Some strong thunderstorms earlier had
moved into Suwannee Valley and I-75 corridor. These storms have
moved eastward and weakened as they moved in line from Baker to
Alachua counties. This morning`s convection was round one. Another
round of showers and storms are anticipated to develop this mid
afternoon through the evening. At this time, a secondary low level
jet max is expected to move through the region. Will have to
watch were the breaks in cloud cover occurs to realize further
destabilization of the lower atmosphere. In the upper levels,
series of weak disturbances will swing through the SWLY flow
which will allow the potential for strong to marginally severe
storms to occur across SE GA and NE FL. The main impacts will be
the potential for some storms to contain heavy rain, hail, and
gust winds of 40 to 60 mph, where SPC has most of the region in a
marginal risk of severe weather. Some storms may train over the
same areas with forecasted rainfall of 1 to 2 inches with locally
3 inches particularly across the Suwannee Valley and SE GA. WPC
has much of the region in slight chance for excessive rainfall for
today. With antecedent ground conditions more saturated from
previous rainfall across interior SE GA and northern Suwannee
Valley will continue the flood watch for this region. The
aforementioned front will press into and through the region during
the late nocturnal, pre-dawn and very early daylight hours with
the 3rd round of showers and thunderstorms anticipated.

Rain chances diminish by midday Thursday as high pressure
approaches but a tight pressure gradient will likely produce
breezy conditions. High pressure and upper ridging should keep the
region dry on Friday and into the weekend with a significant
warming trend into early next week.

&&

.SYNOPSIS...
Issued at 450 AM EDT Wed Mar 27 2024

Early morning surface analysis depicts a wavy frontal boundary
extending from the Appalachians southward through the FL Panhandle
and northern portions of the Gulf of Mexico. Meanwhile, high
pressure (1021 millibars) was building southeastward through the
Plains states in the wake of this front. Aloft...southwesterly
flow was deepening across our region between stout ridging over
the northwestern Caribbean Sea and a northern stream trough that
was digging east-southeastward from the High Plains towards the
Great Lakes region. Otherwise, a southern stream trough was
progressing eastward across west Texas. Waves of convection
continue to push north-northeastward ahead of the slow moving
front from the FL Big Bend and Apalachee Bay and into southwest
and south central GA, with strong convection located just west of
the Alapaha River as of 09Z. Thick cirrostratus was blowing off of
this deep convection and was blanketing locations along and north
of the Interstate 10 corridor, with multi-layered cloudiness
otherwise in place across much of southeast GA. Thinner cirrus was
located over north central FL. Warm air advection on the heels of
a south-southeasterly breeze was keeping temperatures and
dewpoints in the mid to upper 60s nearly area-wide as of 09Z.

&&

.NEAR TERM...
(Today and Tonight)
Issued at 450 AM EDT Wed Mar 27 2024

Waves of convection will gradually overspread western portions of
the Suwannee Valley and inland southeast GA this morning, with
cold pool / convective outflow interactions likely pushing the
leading edge of this convection across the Interstate 10 corridor
this morning. This activity will likely weaken as it moves
eastward and encounters a more stable air mass. A few breaks in
the multi-layered cloudiness are expected to develop during the
early to mid-afternoon hours, which will help to destabilize our
atmosphere. Meanwhile, a trough migrating through the southern
branch of the jet stream across Texas will create a 130-knot jet
streak at 250 millibars (around 35,000 feet) downstream of this
feature, with this jet streak becoming aligned over the Deep
South this evening. This feature will develop a wave of low
pressure along the frontal boundary over Apalachee Bay late this
afternoon, with this feature then progressing northeastward across
inland southeast GA tonight.

Strengthening southwesterly flow aloft overtop of the slow moving
surface frontal boundary will lift a batch of shortwave energy
across our area this afternoon. A low level south-southwesterly
jet around 40 knots will accompany the arrival of this shortwave
energy, with ML CAPE values rising to the 1,000 - 1,500 j/kg range
for locations south of Interstate 10 this afternoon. The next
wave of convection will push northeastward from Apalachee Bay and
the FL Nature Coast during the mid-afternoon hours, with activity
expanding in coverage and intensity during the late afternoon and
early evening hours throughout our area. Strong to isolated severe
thunderstorms will be possible, with stronger activity capable of
producing damaging wind gusts of 40-60 mph, hail, and frequent
lightning strikes. Thicker cloud cover today will keep highs in
the 70s for southeast GA and the Suwannee Valley, while breaks in
the cloud cover early this afternoon allow for highs to climb to
the low and possibly middle 80s for north central and portions of
coastal northeast FL.

Additional waves of convection are expected overnight as the wave
of low pressure crosses our region and the cold front begins to
make some eastward progress. Multiple rounds of downpours will
result in widespread 1-3 inch rainfall amounts across our area. We
decided to expand the Flood Watch across additional counties in
interior southeast GA and the Suwannee Valley, where we have a
higher likelihood of localized totals in the 3-5 inch range. That
being said, the Weather Prediction Center has expanded the area of
the Slight Risk of Excessive Rainfall along the I-10 corridor in
northeast FL, and we may need to include additional counties in
the Flood Watch area later today, based on forecast trends.
Localized flooding will be possible nearly area-wide tonight,
especially if downpours train over more normally flood prone
and/or urban locations.

Rainfall will end across inland southeast GA and the Suwannee
Valley overnight, with the cold front expected to approach the
I-95 corridor towards sunrise on Thursday, with downpours
remaining possible into the early morning hours for north central
FL and coastal locations in northeast FL and southeast GA. Cool
air advection on the heels of breezy northwesterly winds will
drive lows down to the mid and upper 50s for inland southeast GA
and the Suwannee Valley by sunrise on Thursday, with 60s expected
ahead of the front elsewhere.

&&

.SHORT TERM...
(Thursday through Friday)
Issued at 450 AM EDT Wed Mar 27 2024

Majority of convection associated with the frontal passage will
disperse and move offshore with a potential for some otherwise,
VFR conditions will prevail through at least 11Z at the regional
terminals.ast lingering developments over southeast Georgia in the
afternoon hours. High pressure conditions will settle in over the
forecast area by the end of the week with clearing skies, dry
weather, and with breezy northeasterly winds becoming more mild
and variable by Friday. Temperatures will dip down during the
latter part of the week with daily highs reaching up into the
lower to mid 70s with overnight low temperatures dropping into the
mid to upper 40s for inland areas.

&&

.LONG TERM...
(Saturday through Tuesday)
Issued at 450 AM EDT Wed Mar 27 2024

High pressure ridging over the region will persist through the
weekend and into the beginning of next week with dry weather
conditions through much of the period. Convection may return to
the region by midweek as the influence of high pressure begins to
diminish and instability ahead of an approaching frontal boundary
moves into the southeast US. Temperatures will experience a
warming trend over the weekend and into the beginning of next week
with max temps rising to be well above average by Monday.

&&

.AVIATION...
(12Z TAFS)
Issued at 757 AM EDT Wed Mar 27 2024

Ceilings are expected to lower to the 3,000-4,000 foot range
towards 15Z at the regional terminals as showers begin to
develop. Thunderstorm chances increase after 18Z, and we indicated
a PROB30 group for gusty winds and MVFR visibilities during
heavier downpours during the late afternoon and early evening
hours. This wave of convection should depart our region by 03Z,
with ceilings expected to lower to IFR. The next wave of showers
with isolated embedded thunderstorms will likely impact the
regional terminals during the overnight and predawn hours on
Thursday. Winds this morning shift to southerly while gradually
increasing to around 10 knots by 16Z. The Atlantic sea breeze will
develop during the afternoon hours, moving across the SGJ
terminal during the mid-afternoon hours, shifting surface winds to
southeasterly at 10-15 knots outside of developing thunderstorm
activity.

&&

.MARINE...
Issued at 450 AM EDT Wed Mar 27 2024

Elevated seas will continue through Thursday, with Small Craft
Advisory level seas of 5-7 feet persisting offshore. Small Craft
should Exercise Caution if venturing into the near shore waters
through tonight, where seas of 4-6 feet are expected. Otherwise, a
slow moving cold front stretching across the Florida panhandle
early this morning will approach our local waters this evening. A
wave of low pressure will develop along this front tonight, with
this feature strengthening as it accelerates northeastward off the
Carolina coast on Thursday. Showers and thunderstorms will
overspread our region this afternoon, with strong to isolated
severe thunderstorms possible over our local waters late this
afternoon through this evening. Stronger activity will be capable
of producing strong wind gusts, hail, and frequent lightning
strikes.

Waves of downpours and embedded thunderstorms will continue along
this slow moving front overnight through Thursday morning,
followed by a surge of northwesterly winds on Thursday afternoon
following the passage of the front. Winds may briefly reach Small
Craft Advisory levels on Thursday afternoon for the offshore
waters before shifting to northerly while gradually diminishing
on Thursday night and Friday. High pressure will then build
directly over our waters on Friday evening before shifting
southward this weekend, allowing for prevailing south-
southwesterly winds.

Rip Currents: A long period east-northeasterly swell will combine
with elevated seas to create a high risk of rip currents at all
area beaches today. Breakers of 4 to 6 feet at the northeast FL
beaches will be slow to subside on Thursday, and another day of
high risk conditions is expected. Breakers of 3-5 feet today at
the southeast GA beaches will subside to 2-4 feet on Thursday,
resulting in a high-end moderate risk.

&&

.HYDROLOGY...
Issued at 450 AM EDT Wed Mar 27 2024

Water levels continue gradually receding all along the Altamaha
River, with minor flooding expected to continue during the next
several days along upper portions of the Altamaha River near the
Baxley gauge. Meanwhile, runoff from more recent rainfall is
resulting in rises along the Satilla River, with minor flooding
beginning along lower portions of the Satilla River near the
Atkinson gauge on Thursday. Additional rises all along the
Satilla River are possible during the upcoming weekend.

A slow moving frontal boundary will impact our region through
Thursday morning. Widespread rainfall amounts of 1-3 inches
are forecast at most locations, and a higher potential for
higher amounts of 3-5 inches is expected across most of inland
southeast GA and northern portions of the Suwannee Valley. The
Flood Watch has been expanded to cover most of inland southeast GA
and northern portions of the Suwannee Valley for this potential.
Localized higher totals are possible across the rest of the
Interstate 10 corridor in northeast FL, where a Slight Risk of
Excessive Rainfall has been issued by the Weather Prediction
Center. We may expand the Flood Watch later today across portions
of northeast FL based on forecast trends.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  75  56  72  45 / 100  90  40   0
SSI  74  61  71  50 /  80 100  70   0
JAX  79  61  74  48 /  60 100  70   0
SGJ  81  65  75  53 /  60  70  60   0
GNV  80  62  75  48 / 100  90  70   0
OCF  83  63  77  48 /  80  90  60   0

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through late tonight for FLZ021-120-220-322-522.

     High Rip Current Risk through late tonight for FLZ124-125-133-
     138.

GA...Flood Watch through late tonight for GAZ132-134>136-149-151-152-
     162-163-250-350-364.

     High Rip Current Risk through late tonight for GAZ154-166.

AM...Small Craft Advisory until 6 AM EDT Thursday for AMZ470-472-474.

&&

$$


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