Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 200801

Area Forecast Discussion
National Weather Service Jacksonville FL
401 AM EDT Fri Oct 20 2017


High pressure will continue to the North with onshore flow pattern
remaining. Weak trough moving ashore early this morning produced a
few showers mainly South of KSGJ. Will keep pops below mention for
Today and Tonight, as additional precip generating troughs difficult
to discern at this time. Although a few light showers can not be
ruled out, mainly for coastal NE FL. With clear skies and cooling
expected over inland SE GA, expect fog development this morning and
again Tonight.

High temperatures Today will be coolest near the coast due to the
onshore flow, with readings ranging from the upper 70s near the
coast to the lower 80s inland. For Tonight the onshore flow will
reverse this trend with warmest readings along the coast.


A deep layer high pressure system centered over the Carolinas
is expected to move northeast through Sunday. This will continue
to result in east to eventually east to southeast flow by Sunday.
Veering winds will moderate temps with highs on Saturday in
the lower to mid 80s...then on Sunday more commonly in the
mid 80s...possibly upper 80s south zones. Lows Sat night becoming
warmer, near 70 along the coastal mid 60s inland.
Patchy fog, possibly dense at times, expected inland areas Sunday
morning. Adequate low level moisture and low level convergence
will support a low risk of a few showers on Saturday...mainly
coastal counties and the marine zones. Increased warm advection,
along with an uptick in moisture levels will provide a chance of
showers and possibly a few thunderstorms with a weakened
subsidence inversion and weak instability.


Moderate to strong warm advection begins the extended period over
the forecast region ahead of a strong cold front and vigorous
mid/upper level trough located across the MS valley. Prefrontal
troughing and rich moisture should result in high rain chances
around the 50-70% percent range. Weak instability warrants just a
slight chance of a thunderstorm Monday. Frontal boundary and
squall line now is sped up a bit in the guidance, and in fact the
GFS and ECMWF are within about 6 hours of agreeing on the frontal
passage occurring early Tuesday. Thus, we have high end likely
POPs for Mon night with potential for scattered thunderstorms. Not
much instability to work with due to cloud cover and nocturnal
cooling but still a low end threat of strong to possibly severe
storms (Mon night - Tue morning) given low level jet up around 45
kt and strong cold front. Deep moisture will be sliding eastward
along with squall line on Tuesday, followed by drier air/more
stable conditions. Secondary push of cool air may move in late
Tuesday afternoon and late evening. Sfc high pressure to our west
on Tuesday will build in across the north Gulf of Mexico and move
to northern FL on Thursday. Fall-like temps, cooler than normal,
expected Wed through Thu...with mostly clear skies. Coolest temps
in a long while (since early May 2017) occur Thursday morning with
lows forecast in the mid to upper 40s inland areas...and lower to
mid 50s near the coast.



High pressure will remain to the North of the region this 06z TAF
period. This will continue onshore flow pattern with stratus moving
inland with a few showers possible. The best chance for restrictions
with these showers and stratus will be over NE FL, mainly for KSGJ.



High pressure will be North of area waters into Saturday, then to
the Northeast Saturday night into Monday. A strong cold front will
sweep across the region from the West Monday night into Tuesday. A
strong line of storms will be possible as this front moves through.

Rip Currents: the high risk of rip currents is continued through
late Saturday due to lingering east swells and onshore flow.


.HYDROLOGY...Water levels along the local Atlantic coast
continue to lower to action stages with the passage of the New
Moon and gradually weakening onshore flow. High tides have been
cresting at low end moderate stage in the St. Johns River basin
south of downtown JAX with levels in the minor to barely moderate
in Duval county/JAX Metro area. At this time, decided to extend
the coastal flood warning for the St. Johns basin, through
Saturday morning.


AMG  81  59  83  63 /   0   0   0  10
SSI  76  71  80  70 /   0  10  10  30
JAX  79  69  83  67 /  10  10  20  20
SGJ  79  73  81  72 /  10  10  20  20
GNV  82  67  86  66 /  10  10  10  10
OCF  84  66  86  68 /  10   0  10  10


FL...High Rip Current Risk through Saturday evening for Coastal Duval-
     Coastal Nassau-Flagler-St. Johns.

     Coastal Flood Warning until 8 AM EDT Saturday for Clay-Coastal
     Duval-Flagler-Inland Duval-Putnam-St. Johns.

GA...High Rip Current Risk through Saturday evening for Coastal
     Camden-Coastal Glynn.

AM...Small Craft Advisory until noon EDT today 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.



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