Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 210713
AFDJAX

Area Forecast Discussion
National Weather Service Jacksonville FL
313 AM EDT Sat Oct 21 2017

...STRONG COLD FRONT MOVES THROUGH ENTIRE REGION LATE MONDAY/EARLY
TUESDAY...

.NEAR TERM /TODAY-TONIGHT/...

Today...High pressure will remain in control at the surface and
aloft just NE of the region with an onshore easterly flow
continuing. This will continue the threat of coastal showers that
will press further inland later on this afternoon. Breezy onshore
flow at 15-20G25-30 mph will continue at the coast with 10-15G20
mph inland. High clouds will slowly increase from the W/SW through
the day but not enough to keep Highs from reaching mid/upper 80s
inland and lower 80s along the coast.

Tonight...Steering flow becomes more SEly and moistens with clouds
and shower chances increasing along the coast from JAX northward
into SE GA. Scattered rain showers will push inland to at least
the US 301 corridor as skies become partly to mostly cloudy. Lows
will be a bit more mild in the mid/upper 60s inland and lower 70s
along the coast.

.SHORT TERM /SUNDAY THROUGH TUESDAY/...

Sunday...Low level flow turns from east-southeast Sunday as
southern periphery of the surface high pressure pulls northeast
from the SE US Mid Atlantic region to New England. As a result...
increasing warm air advection and moisture on Sunday will lead to
a chance of showers and possibly a few embedded thunderstorms on
Sunday afternoon. Highs on Sunday will be in the low 80s along the
coast and the mid 80s inland.

Sunday night...The surface ridge will extend off the northeast US
over the adjacent Atlantic to the mid Atlantic while an upper
level ridge will reside just offshore. Low level flow will remain
and veer further to the SE. Precipitable water values increase
during the nocturnal hours particularly north of I-10 and over SE
GA between 1.9 to 2.0 inches. Widely scattered showers are
forecast near the First Coast and Suwannee Valley into SE GA with
isolated showers south of I-10 over interior NE FL. Temperatures
will be warm Sunday night, with lows in the upper 60s to lower 70s
interior to mid 70s along the coast.

Monday... Low level convergence associated with encroachment of
the pre-frontal trough ahead of the front bisecting Alabama by
afternoon will heighten POPs Monday ranging from 60 to 80% north
of SR16 offshore and 40-60% south of SR16. It will be warm and
humid Monday with temperatures 3 to 5 degrees above normal but no
record highs expected with abundant cloud cover. Weak instability
warrants just a slight chance of a thunderstorm across north
central Florida and near the the Altamaha River Basin with CAPES
of 850-1000.

Monday night and Tuesday...A cold front is forecast to move into
the region Monday night and then clear the region Tuesday morning.
The best dynamics will push off to the east and northeast of the
region by the time trough arrives, with the deeper moisture
pushing out into the Atlantic. The instability will be even lower
due to cloud cover and nocturnal cooling, but there is still a low
end probability of strong to possibly severe storms (Mon night -
Tue morning) given low level jet up around 45kt and strong cold
front. Drier conditions will push through the region on Tuesday
afternoon. Lows Monday night will be mid 60s across the interior
and upper 60s to lower 70s I-95 to the coast. Tuesday afternoon
highs will be in the mid 70s to lower 80s.

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...Strong high pressure
will build form over the Lone Star state and Southern Plains
Tuesday night. This feature will then build into the Gulf of
Mexico Wednesday pushing into Florida Thursday. A secondary push
of colder and drier air will make its way through the region
Tuesday night and Wednesday. This will finally bring Fall-like
temperatures, with lows in the 40s across much of the region
Thursday morning, except the coast in the lower to mid 50s. Highs
will struggle to reach the 70 degree mark across the region
Wednesday and Thursday. Modest return flow develops beginning late
Thursday night into Friday as high pressure pushes offshore as
max temps Friday push into the mid 70s.

&&

.AVIATION...
Generally VFR except for some patchy MVFR VSBYS in fog at GNV/VQQ
this morning depending how thick cirrus aloft may become.
Otherwise the onshore flow will continue to provide for SCT to BKN
clouds at 3000-5000 ft along the coast but rain chances low enough
to keep out of the TAF forecast for now.

&&

.MARINE...
Small Craft Exercise Caution (SCEC) conds will continue into
early next week as E/NE winds at 15-20 knots and seas 4-6 ft will
slowly veer to E/SE on Sunday and SE/S on Monday. Winds/Seas will
be close to Small Craft Advisory (SCA) levels with the frontal
passage by Tuesday/Wednesday as they shift W/NW.

Rip Currents: High Risk Today with breakers/surf in the 3-5 ft
range due to the onshore flow and continuing swells. Onshore flow
and swells may subside enough to allow for Moderate Risk on
Sunday.

&&

.HYDROLOGY...
Tidal Flooding on the St Johns River Basin continues to slowly
subside as onshore flow weakens and will lower Coastal Flood
Warning to an Advisory for all areas along the river except for
areas in Putnam County where Moderate flooding still possible for
a few more high tide cycles.

&&

.PRELIMINARY POINT TEMPS/POPS...
AMG  84  64  84  70 /   0  30  30  40
SSI  80  72  81  75 /  20  40  30  50
JAX  83  70  84  71 /  20  50  30  40
SGJ  83  72  83  73 /  40  40  30  40
GNV  85  67  86  70 /  10  20  30  20
OCF  86  67  87  71 /   0  20  50  10

&&

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

     Coastal Flood Advisory until 6 AM EDT Monday for Clay-Coastal
     Duval-Flagler-Inland Duval-St. Johns.

     Coastal Flood Warning until 6 AM EDT Monday for Putnam.

GA...High Rip Current Risk through late tonight for Coastal Camden-
     Coastal Glynn.

AM...None.
&&

$$

Hess/Cordero



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