Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 250847
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
445 AM EDT Sat Mar 25 2017

.SHORT TERM...
Sfc ridge will continue to dominate the region with the axis
across the wrn ATLC and into the ne Gulf of Mexico. Prevailing
flow will be east to southeast with plenty of moisture beneath a
6000-7000 ft subsidence inversion. Anticipate partly to locally
mostly cloudy skies from cumulus/stratocumulus...with some sct
cirrus at times as well ahead of an approaching upper level
trough. A few showers possible over the coastal waters and can`t
also rule out a few sprinkles over land areas and perhaps a brief
light shower. Overall chances over land though are below 15
percent. Highs today expected to be around 80 inland and mid 70s
along the coast.

Tonight...Mid to upper level trough approaches the area with a
plume of moisture encroaching on our western zones in the evening
and passing through overnight. There`s not a lot of forcing and
the moisture is not all that impressive. Could be a few showers
develop after midnight and patchy fog possible over the srn zones
where winds will be light to calm. Prevailing flow in the low
levels expected to be southeast to south so another mild night
with lows in the 55-60 deg range.

Sunday...Mid to upper level trough will be over the region in the
morning hours and begins to lift out in the late aftn. There`s
little to no sfc reflection of the trough and main low level forcing
for precip will be aftn sea breezes and aftn heating. Based on model
consensus will continue with a low 20-30 chance of showers and
tstms...though GFS is still the odd one out with likely POPS over SE
GA. Instabilty values for CAPE look to be around 700-1000 J/kg with
a max of up to 1400 J/kg possible over inland SE GA. Highs will be
held down a bit by increasing clouds but southerly flow will
compensate for that. Forecasting highs in the lower 80s inland and
around upper 70s near the coast.

Shortwave troughing that will move across the mid-Mississippi,
Tennessee and Ohio Valley regions on Sunday will continue to
progress east-northeastward through the eastern Great Lakes by
Sunday evening. Scattered convection triggered by a vorticity lobe
extending from this trough and potential sea breeze interactions on
Sunday afternoon may linger into the evening hours over the northern

Suwannee Valley and portions of inland southeast GA. Meanwhile,
another shortwave trough emerging from the Colorado Rockies on
Sunday will progress eastward through the Southern Plains states on
Sunday night. High cloudiness from this feature may approach western
portions of our region, but we expect a rather humid air mass to
prevail locally as low-level south-southwest flow prevails. Low
clouds and fog will be possible by the predawn hours on Monday
across much of our area. Above normal low temperatures will prevail,
with most areas only falling to the 55-60 range.

West-southwest flow will strengthen aloft on Monday as the shortwave
trough progresses E-NE through the Mississippi, Tennessee, and Ohio
Valley regions on Monday. Low-level ridging will remain centered
near the FL peninsula, keeping a relatively weak pressure gradient
in place locally. This will promote sea breeze development during
the afternoon along both the Gulf and Atlantic coasts, with these
boundaries progressing inland during the mid to late afternoon
hours. Temperatures aloft will be cooling over our region on Monday,
but the lack of deep layered moisture may limit convective
development along sea breeze boundaries, which should collide over
the Suwannee Valley during the late afternoon hours. We have
indicated widely scattered late afternoon and early evening
convection in the forecast grids for locations west of the St. Johns
River basin and west of I-95 in southeast GA. Low level ridging and
plenty of morning sunshine will boost highs in the low to mid 80s
inland, with the early afternoon sea breeze keeping coastal highs in
the mid to upper 70s.

Shortwave energy progressing through northern GA on Monday evening
may keep isolated to widely scattered convection going through the
early evening hours over southeast GA. Otherwise, low level
southwesterly flow will prevail overnight, with a relatively warm
air mass persisting for our region. Low clouds and fog may develop
during the predawn hours on Tuesday, as lows only fall to the upper
50s and lower 60s.

.LONG TERM (Tuesday through Saturday)...
A shortwave trough that will be passing through northern GA on
Monday night will progress eastward through the Carolinas on
Tuesday. As the base of this trough bypasses our region to the
north, a drier NW flow pattern will overspread our region as the day

progresses on Tuesday. There may be enough lingering moisture and
forcing from the bypassing trough aloft for some isolated convection
to develop near the Altamaha/Ocmulgee Rivers on Tuesday afternoon.
Otherwise, light southwesterly low level flow will prevail as weak
surface ridging persists over the FL peninsula. This weather pattern
will allow highs to soar into the mid/upper 80s inland, with an
afternoon sea breeze keeping coastal highs closer to 80. Warm
conditions will prevail Tuesday night, with low clouds and fog again
a possibility over much of the area, as lows generally fall to the
upper 50s and lower 60s.

Heights aloft will rise on Wednesday and Thursday downstream of a
potent shortwave trough that will dig from the desert southwest
through Texas. The 00Z GFS depicts a weak lead shortwave troughs
progressing across GA on Wednesday and Thursday afternoons, which
could spark isolated late afternoon convection, mainly for locations
north of Interstate 10. Otherwise, an early season heat wave is
expected to develop at inland locations, which will experience highs
in the upper 80s. Alma (GA) will approach or break their daily
record highs on Wednesday and Thursday. A loose local pressure
gradient will promote early afternoon sea breezes along the Atlantic
coast, which will again keep highs closer to 80 for the beaches.
Lows Wednesday night will again only fall to the upper 50s and lower
60s, with fog and low cloud development a good possibility for much
of our region.

Deep-layered ridging will remain anchored near the Bahamas later
this week, which will likely deflect the potent shortwave trough
over Texas northeastward. Significant differences exist with the 00Z
global models as far as how much troughing is able to dig into the
southeastern states. For now, model blends indicate widely scattered
convection possibly reaching our western counties on Thursday night
and early Friday.
Scattered convection is then indicated area-wide on Friday. However,
the 00Z ECMWF is not enthusiastic with rainfall chances over most of
northeast and north central FL, with higher chances expected in
southeast GA and perhaps the western Suwannee Valley as ridging
aloft deflects greater forcing to the north of our region.
Increasing clouds ahead of this system should keep highs in the low
to mid 80s inland, with sea breezes resulting in highs in the
mid/upper 70s at the coast. Rain chances will likely decrease on
Saturday as troughing aloft departs our area.
Above normal temperatures will likely prevail through next weekend.

&&

.AVIATION...
Prevailing VFR conditions expected next 24 hours with a slight
chance of MVFR cigs around VQQ and possibly near the coast. CIGS
mainly in the 4000-6000 ft range at times through this evening.
Winds will be light east to southeast early then become about 10
kt during the day.

&&

.MARINE...
Winds and seas continue to slowly diminish but will hold onto SCA
for outer waters offshore of NE FL at this time through late
morning. Rest of areas today around 3-6 ft. SE flow to continue
over waters the next several days with strong high pressure
remaining offshore of the mid-Atlantic coast. Winds will gradually
weaken during the next several days.

Rip Currents: buoy data at 41112 shows 4-5 ft seas with periods of 8
seconds and low level flow is about 10-12 knots. This suggests we
are near high risk for the NE FL beaches so will go with high risk
for today with moderate risk for SE GA. A bit lower risk for Sunday
as seas continue to slowly diminish.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  79  58  80  58 /  10  10  30  20
SSI  73  60  75  60 /  10  10  10  10
JAX  78  57  80  58 /  10  10  20  10
SGJ  77  61  78  61 /  10  10  10  10
GNV  81  57  82  57 /  10  10  20  20
OCF  81  58  82  58 /  10  10  20  20

&&

.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through this evening for Coastal Duval-
     Coastal Nassau-Flagler-St. Johns.

GA...None.
AM...Small Craft Advisory until 11 AM EDT this morning for Waters
     from Altamaha Sound GA to Fernandina Beach FL from 20 to 60
     NM-Waters from Fernandina Beach to St. Augustine FL from 20
     to 60 NM-Waters from St. Augustine to Flagler Beach FL from
     20 to 60 NM.

&&

$$

Shashy/Nelson



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