Area Forecast Discussion
Issued by NWS Jacksonville, FL

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FXUS62 KJAX 180920

Area Forecast Discussion
National Weather Service Jacksonville FL
420 AM EST Sat Nov 18 2017

Patchy fog and some low clouds will be around early this morning as
moisture off the Atlantic along with clear skies enabling formation
of radiation fog over the forecast area. Temps in the upper 40s to
lower to mid 50s are noted at 3 AM. Local visibilities will briefly
be down to less than 1 mile. Sfc high pressure noted over the NC
outer banks with a weak coastal trough along our coastline. This
high pres system is in the process of moving eastward. A cold front
is well to our west across the central Plains trailed from a 993 mb
sfc low over southeast KS at 3 AM.

Sfc high pressure over ern NC will shift quickly eastward through
tonight as the fast moving cold front will march steadily east-
southeast while sfc low over the Plains moves northeastward. Airmass
across the local area is fairly dry and low level winds will turn
from an east direction to south and southwest today. Any fog and
stratus around before 9AM should rapidly dissipate as daytime
heating begins. Modest warm advection and mostly sunny skies will
bring highs warmer than normal with forecast of highs around 75-80.
Favored the warmer GFS MOS temps today. Tonight...changes will be
coming our way as the front will enter our forecast area after
midnight accompanied by a sharp wind shift, enough moisture and
upper level support to generate at least scattered shower activity.
High POPs are placed over inland southeast GA around 40-50 percent.
Skies will be mostly clear in the evening before front
arrives...with increasing clouds and forcing arriving late. Timing
of the front...expected to move into our inland southeast GA zones
about 4AM, then located from St Simons Island to Live Oak around
sunrise Sunday morning. Mixing of the boundary layer and increased
clouds will result in min temps leveling off around the mid to upper

.SHORT TERM (Sunday-Monday night)...

Fast moving cold front will sweep through the area Sunday morning
bringing scattered showers. Moisture and dynamics limited so
rainfall amounts are expected to be limited. Skies will clear from
northwest to southeast during the day as cool high pressure builds
in from Texas and the lower Miss valley. Cold air advection will
keep high temps held to the lower to mid 60s across Se Ga and upper
60s to near 70 across Ne Fl. High pressure moves into N Ga and Tenn
Valley Sunday night providing light winds and rather cold temps
across areas from the Suwannee Valley into inland Se Ga where min
temps will dip into the mid/upper 30s while coastal areas will be at
least 10 degrees warmer with a north breeze. High pressure moves
across the Carolinas Monday providing a continuation of the cool and
dry conditions. As the high moves offshore Monday night...return
flow will bring milder temps to the area with an increase in clouds
as a short wave trough approaches the area.

.LONG TERM (Tuesday-Friday)...

Short wave trough traverses the area on Tuesday bringing a chance of
showers with best rain chances along the Ne Fl coast as it interacts
with a coastal trough. Could be a potentially wet extended period
depending on how conditions evolve with the next trough. The 00Z run
of the ECMWF has drastically changed as it moves a series of short
wave troughs across the area which brings a chance of showers to
areas mainly across the far south for the rest of the week. This is
very different from the 00Z GFS which still has a closed low diving
Se from the lower Miss Valley into the northern Gulf and then Ne
across the region which will bring more widespread rain to the area.
Due to the major differences between the models...have chosen to
take the middle ground and go with continued chance pops with
highest pops across the far south and gulf coast. Due to cloud
cover...max temps held to below normal especially mid to late week.
Confidence low on thunder so have left that out for now.


.AVIATION...Challenging TAFs with shallow fog resulting in ocnl
LIFR or less around JAX, VQQ and CRG. This should continue until
around 12z-13z. GNV will likely see ocnl IFR until 13z as well. With
daytime heating, any fog and stratus will quickly dissipate this
morning with generally southerly flow at or below 10 kt. Winds will
end up more southwest late Sat night ahead of an approaching cold
front. Low CIGS and LLWS issues look possible after 06z Sun due to
the cold front approaching.


.MARINE...Light onshore flow early today will transition to
southerly as a cold front approaches the region. Southwesterly winds
will increase to near 20-25 kt toward early morning for offshore
waters so have hoisted SCA. SCA is currently forecast go through
Sunday afternoon but could very well continue longer but for now
uncertain on winds Sun aftn-Mon so will have to be monitored for
possible extension. High pressure will build in behind the front
Sunday with the high directly north of area waters Monday night. The
high will shift northeast of the region through mid week while
another frontal system pushes through the area, though
greater uncertainty on the details due to model differences.

Rip Currents: Low risk for southeast GA waters and low end
moderate for northeast FL beaches.


AMG  77  56  63  36 /   0  50  20   0
SSI  74  61  66  46 /   0  30  40   0
JAX  79  58  68  44 /   0  20  40   0
SGJ  78  60  71  49 /   0  10  40   0
GNV  78  58  69  39 /   0  20  50   0
OCF  78  58  72  41 /   0  10  50   0





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