126
FXUS62 KJAX 131743
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
143 PM EDT Mon May 13 2024

...New AVIATION...

.UPDATE...
Issued at 1117 AM EDT Mon May 13 2024

A couple of tweaks to discuss this morning on the forecast
through this afternoon:

 1) The PoPs and cloud cover were both increased for the inland
zones, mainly north of I-10, to account for the earlier batch of
light and stable rain associated with the lift being supplied by
a shortwave impulse propagating through the zonal flow. A few
storms are possible as this wave pushes across the area this
afternoon, mainly south of I-10 and west of the St Johns River
where marginal instability will build as SSE flow advects higher
dewpoints into north-central FL.

2) Due to the thickening high cloud cover, temperatures were
trended downward to reflect the latest observations and cool
expected high temps to the upper 70s and low 80s across southeast
GA.

--------------------------------------------------------------

Otherwise, the Atlantic sea breeze is still expected to push
inland and interact with the Gulf sea breeze west of the Highway
301 corridor this afternoon, mainly trigger garden-variety
convection.

For this evening, SPC has maintained a Marginal Risk (Level 1 of
5) for the area while WPC has nudged a Slight Risk (15% chance of
flooding) a bit eastward into portions of the Suwannee Valley.
Both of these Risks are aimed at the severe and heavy rain threats
associated with thunderstorms during the evening hours as a warm
front begins to lift into the region.

For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf

&&

.NEAR TERM...
Issued at 300 AM EDT Mon May 13 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

A few sprinkles are moving across the region as of 06-07Z, in
response mainly to a pseudo warm front passing overhead as weak
high pressure moves northeastward. This is setting the stage for
the start of an active few days, as a more robust warm front
approaches the region this afternoon and evening. The timing of
this also coincides with the diurnal heating cycle and therefore
an onshore sea breeze, which should help to induce convection over
northeast FL. At the same time, shortwave energy/diffluence aloft
associated with a larger upper trough over the south/central US
streams east/northeast along the Gulf coast and across southeast
GA.

The combination of all these features will result in increasing
shower and t`storm coverage throughout the afternoon and evening,
likely continuing into at least the first half of tonight.
Although plentiful ingredients are in place, the main limiting
factor will be instability, as SB/MUCAPE is expected to be
generally around 1000 J/kg, decreasing further north and east and
especially over southeast GA. Despite this, with the modest
dynamics and frontal boundary, the SPC still places the entirety
of the CWA in a "marginal" risk for severe storms. The main
threats will be gusty winds, hail, and heavy rainfall - though an
isolated tornado cannot be ruled out as well. Looking like the
best "overlap" of ingredients will be around I-10 southward,
though southeast GA certainly cannot be totally overlooked as
well. Temps today will be a bit tricky due to the amount of cloud
cover likely to be in place (which also will play a big factor in
the amount of buoyancy available). However, expecting mid 80s to
low 90s south of about I-10 and low 80s and some upper 70s over
southeast GA. Expecting a break for most about after midnight
through the morning hours, with a mild night of upper 60s to
low/mid 70s.

&&

.SHORT TERM...
(Tuesday through Wednesday night)
Issued at 300 AM EDT Mon May 13 2024

Tuesday...Warm frontal boundary still on track to be somewhere
near the FL/GA border early in the day with likely ongoing
convective complex along this boundary close to/or just west of
the local area and expect this feature to push across the entire
area at some point during this time frame with heavy rainfall and
isolated strong to severe storms expected. Rainfall totals still
expect to be highest along and to the north of the warm frontal
boundary with localized 2-4 inch amounts across SE GA and 1-2 inch
amounts across NE FL. Damaging winds will remain the main storm
threat, but large hail and/or isolated tornadoes cannot be ruled
out. Max temp forecast a bit tricky due to possible timing issues
with storm activity but widespread highs in the 80s expected, with
some lower 90s possible across NE FL south of a line from Ocala to
St. Augustine. Even without storm activity expect the gradient
wind flow to be out of the Southwest from 15-25 mph with gusts to
35 mph at times, strongest in the warm sector across NE FL.

Tuesday Night...Mid to upper level trough sweeps into SE GA
through the night with dry slot of air aloft pushing the frontal
boundary with numerous showers and isolated strong/severe storms
with heavy rainfall from SE GA during the evening hours slowly
southward into NE FL during the overnight hours with waves of
storms moving along this boundary during this time frame. Training
of storms over already wet soils in some areas from this pattern
set up may require the issuance of a Flood Watch for some areas on
Tuesday ahead of this event. Low temps generally near 70 with
gusty Southwest winds continuing at 10-20 mph with gusts to 30 mph
at times.

Wednesday...Models trending towards dry slot aloft pushing in
faster and driving trailing frontal boundary with showers/storms
and heavy rainfall south of the region quicker than previous model
runs, but for now have kept rainfall chances mainly during the
morning hours across all areas, then shifting southward through NE
FL during the early to mid afternoon hours with some partial
clearing by the end of the day as frontal boundary pushes into
Central Florida. Max temps generally in the mid/upper 80s with
winds shifting to the West at 15-20 mph with gusts to 30 mph at
times.

Wednesday Night...Drier airmass overspreads the local area with
mainly dry conditions after sunset and skies becoming mostly clear
and temps falling into the 60s area-wide behind the frontal
passage.

&&

.LONG TERM...
(Thursday through Sunday)
Issued at 300 AM EDT Mon May 13 2024

Thursday...Lingering dry airmass in place between weather systems
will continue mainly dry conditions with above normal temps
reaching into the upper 80s/lower 90s over inland areas with West-
Northwest winds at 10-15 mph and East Coast sea breeze remains
pinned closer to the Atlantic Coast along the I-95 corridor.

Friday/Saturday...Another similar scenario with warm frontal
boundary lifting back northward on Friday and trailing frontal
boundary pushing southward through the region on Saturday with
heavy rainfall and isolated strong to severe storm potential area-
wide and rainfall chances already in the 50-70% range. Above
normal temps will continue.

Sunday...Lots of long range model uncertainty as some models push
drier air into the region, while some stall the frontal boundary
in the vicinity so for now the model blends are just placing
normal diurnal scattered convection due to local sea breeze
activity as above normal temps continue.

&&

.AVIATION...(18Z TAFS)
Issued at 142 PM EDT Mon May 13 2024

Complex forecast over the next 24 hours with multiple waves of
thunderstorms, some severe. Breezy southeasterly winds will
continue as MVFR cumulus ceilings build this afternoon. First wave
of rain and embedded storms will begin over the next few hours
and be followed by continued bouts of activity through around
03-06z. Combination of rainfall and a lifting warm front tonight
will lower ceilings to a low-MVFR and IFR. As the front lifts,
winds will turn southerly around 10 knots or less. There is more
uncertainty regarding the second round of storms on Tuesday which
appears to accelerate across the area between 12-16z. Threats
with the second round will be primarily considerable winds
potentially up to 50 knots, isolated tornadoes and small hail.

&&

.AVIATION...
(12Z TAFS)
Issued at 649 AM EDT Mon May 13 2024

Overall thinking has not changed significantly since the last
forecast. VFR is expected to continue through early this afternoon
as cloud decks above 030 move in later this morning. Expecting
convection to increase this afternoon and evening, with TEMPO
groups now added for similar timing to the earlier forecast as
well as a continued gusty wind potential. Isolated storms may be
strong to severe, with gusts up to 40-60+ knots. More detail to
TEMPO groups will be added throughout the day as the event
unfolds.

SHRA/-RA lingers tonight as more significant convection moves
offshore. MVFR conditions will be likely for most of the night for
this same period, and IFR also appears possible through the end of
the forecast period.

&&

.MARINE...
Issued at 300 AM EDT Mon May 13 2024

Southeasterly winds increase through today as a warm front lifts
northward toward the coastal waters. This will result in Small
Craft Advisory conditions this evening and overnight tonight. Showers
and storms will spread over our local waters this afternoon and
into the evening ahead of the aforementioned warm front. Tuesday,
the front stalls just north of the local waters as several rounds
of heavy showers and storms push across the area through
Wednesday. Conditions improve on Thursday as weak high pressure
and offshore flow develops.

Rip Currents: Rip current risk will be low to moderate given the
offshore or along shore wind developing today and into Tuesday.

&&

.HYDROLOGY...
Issued at 240 PM EDT Sun May 12 2024

From Monday to Wednesday, forecast storm total rainfall amounts
are from 2 to 3 inches for southeast GA to about 1 to 2 inches for
northeast FL. This may be enough to raise river levels a bit but
for now no minor river flooding is forecast. The high- end
potential total rain is over 5 inches in some locations, mainly
favoring nrn half of the area, so we will need to monitor trends
in the guidance for further updates to the forecast rainfall.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  79  67  83  69 /  90  80 100  70
SSI  81  70  84  72 /  80  80  90  70
JAX  83  69  89  71 /  70  80  90  70
SGJ  83  71  91  71 /  60  70  80  60
GNV  87  69  89  71 /  70  70  80  70
OCF  89  71  92  71 /  60  60  70  60

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...Small Craft Advisory from 5 PM this afternoon to 11 AM EDT
     Tuesday for AMZ450-452-454.

     Small Craft Advisory from 5 PM this afternoon to 2 PM EDT
     Tuesday for AMZ470-472-474.

&&

$$