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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

                            
872 
FXUS62 KKEY 280818
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
418 AM EDT Wed Jun 28 2017

.DISCUSSION...
Currently - A fairly flat pressure pattern is in place across the
Florida Keys, due to a blunted surface ridge ending around the 
Bahamas, and weakening surface trough extending from our area to 
northeast of the northern Bahamas. Winds are light and mostly east
to southeast. A number of outflow boundaries are present across 
our area, and are the initiation points for isolated shower and 
thunderstorm development. Meanwhile, another surface high 
blanketing the eastern United States is migrating eastwards into 
the Atlantic.

Forecast - Surface winds will remain light and mostly east to
southeast today with the rather flat pressure gradient 
continuing. Day time heating over Florida will skew winds on 
adjacent waters. The weakness of the flow through the lower levels
may allow for cloudline formation today and tomorrow. This along 
with any marine boundaries and normal instability and moisture 
justifies maintaining low chance pops through the next few of 
days.

Beginning Thursday, the previously mentioned high pressure system
moving off the Atlantic seaboard will gradually consolidate with 
the ridge to our northeast and become aligned further north. 
Meanwhile, the weak surface trough near our area will dissipate. 
This will result in a gradually strengthening east to southeast 
flow in the Thursday through Saturday time frame. Meanwhile, much 
drier air will move in through the lower levels. Medium range 
guidance reflects these changes with pops dipping well below 20 
percent. Will maintain slight chance pops for late Friday through 
late Saturday.

Through the remainder of the weekend into early next week, the 
ridge will continue marching eastwards into the Atlantic, and the 
local pressure gradient will gradually open up, letting winds
trend slowly downwards. Guidance suggests a mid latitude trough 
will bifurcate the low to mid level ridge. This should result in
increased mid level moisture and bring a bit more instability,
along with windows where lower level flow becomes favorable for
cloud line formation. Will maintain a low chance pops from Sunday.

Seasonably warm and humid surface conditions will continue.

&&

.MARINE...
Weak flow will continue today into tomorrow due to a rather flat
pressure gradient. A high pressure system moving off the mid
Atlantic coast will result in winds trending up beginning late
Thursday. Periodic marine cautions may be required every evening for
the Florida Straits from Thursday night into the weekend due to 
the usual evening surge encountered on an easterly flow. 
Thereafter, the pressure gradient will gradually open up as the 
high to our north moves off into the central North Atlantic.

&&

.AVIATION...
VFR and light/variable breezes will prevail at the EYW and MTH 
terminals this morning. Vertical wind profiles are expected to be 
favorable for moist convection along the island chain this 
afternoon. We have advertised an implied cloud line in both TAFs, 
but will wait until this morning's RAOB before including impacts at 
either terminal.  

&&


.PRELIMINARY POINT TEMPS/POPS...
Key West  89  81  89  81 / 30 30 30 30 
Marathon  91  81  91  81 / 30 30 30 30 

&&

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

&&

$$

Public/Marine/Fire...11
Aviation/Nowcasts....CLR

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