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658
FXUS62 KKEY 062024
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
324 PM EST Fri Dec 6 2019

.DISCUSSION...
Water vapor imagery depicts quite clearly a large upper level
ridge situated from roughly the eastern Pacific to the middle of
the Caribbean. To the north a weakening upper level low is across
MS/AL and moving more east than southeast now. Further upstream
the next upper level low remains over the Pacific, poised to move
into the Pacific Northwest and West Coast regions. This feature
will bear watching as it could bring our next front midweek next
week.

Closer to home, the surface high that was over the Carolinas, has
emerged over the western North Atlantic and continues to move
east. As it moves east, the gradient over the Upper Keys has relaxed
enough to allow winds to veer from NE to E. Winds across the Lower
and Middle Keys remains from the NE as a secondary weak high
pressure cell is developing over the extreme eastern Gulf of
Mexico in between the departing high to the east and an
approaching weak surface low to the west. The weak low is
currently centered over southern LA and is drifting southeast.
Upstream a large high pressure cell is located over the Upper
Mississippi River Valley and moving eastward. Taking a look at
surface observations, temperatures have warmed up into the mid 70s
with dew points in the low to mid 60s. Meanwhile, visible
satellite imagery shows sunny skies across the Middle and Lower
Keys with some fair weather cu moving butting up against the Upper
Keys.

Tonight through Saturday, the aforementioned weak surface low will
continue to drift southeast into the eastern Gulf of Mexico and
dissipate. The weak surface high developing over the extreme
eastern Gulf will eventually become absorbed into a new high
pressure cell that is moving east from the Upper Mississippi River
Valley by late Saturday. Before this occurs, our winds will relax
to almost calm across the island chain, while remaining light over
our waters. During this period, subsidence along with dry air
still in place will keep precipitation chances to near 0 percent.

By Saturday night/Sunday, the high pressure will move off the New
England coast and build southward. This is turn will strengthen
the gradient and lead to an increase in winds across the entire
region. In addition, a meager moisture return is anticipated with
an east to southeasterly return flow. As it stands we are keeping
slight chances for showers returning to the Keys for the first
time since the week before Thanksgiving. After Sunday, the high
will slowly continue its eastward trek and as such, the wind
gradient will gradually relax into Tuesday. This gradual decline
will be short lived as the next potential front descends across
the SE US. There is still some uncertainty in the front`s
position on Wednesday and even less certainty in an upper level
trough that will quickly sweep southeast into the northern Gulf on
Friday. The GFS and ECMWF are coming closer to a solution on the
Wednesday front, keeping the majority of the focus and moisture to
our north, while still bringing in stronger winds.

&&

.MARINE...
High pressure has moved offshore of the Carolina coast and will
continue to trek eastward. Expect winds to gradually diminish
through Saturday. A new high pressure cell will emerge off the New
England coast and build southward, resulting in freshening NE/E
breezes. Winds gradually diminish again starting Monday and
lasting through Tuesday. An approaching front will lead to
additional freshening of breezes with the potential for small
craft advisory headlines. As it stands, no watches, warnings, or
advisories are active across the Florida Keys` waters.

&&

.AVIATION...
A dry and stable air mass will continue for the next 24 hours, due
partly to gentle northeast surface winds continually renewing the
dry air. As a result, clear skies will continue through at least
tonight over the terminals, with shallow strato-cumulus clouds over
the adjacent warm waters of the Gulf Stream.

&&

.CLIMATE...
Record high 88, 2016 was recorded at the Marathon Airport. This
is also tied for the warmest temperature ever recorded in
December.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&

$$

Public/Marine/Fire...LIW
Aviation/Nowcasts....Haner
Data Collection......NB

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