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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

                            
000
FXUS62 KKEY 210930
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
530 AM EDT Mon May 21 2018

...Well above normal rain chances with some heavy rainfall 
   likely...

.DISCUSSION...
.CURRENTLY...
Under mostly cloudy skies and a steady east to southeast wind, 
temperatures are averaging in the mid 70s along the island chain. 
Meanwhile, local radars are detecting scattered showers and a few 
thunderstorms in our county warning area. Surface wise, a western 
Atlantic ridge extends into the extreme Southeast United States, a
trough of low pressure is located in the southeast Gulf of Mexico
along with another trough lingering in the western Caribbean 
Seas. On our marine district, winds are east to southeast varying 
from 9 knots at Pulaski Shoal Light to 20 knots at both Sombrero 
Key Light and Molasses Reef Light. 

&&

.SHORT TERM...(Today through Wednesday night)
An Abundance of moisture will remain in place over the next
several days, but it appears the best low level confluence from 
the east and large scale ascent migrating northward from the 
northwest Caribbean Sea will be tonight into Tuesday. Otherwise, 
our region will remain in a blocked synoptic scale pattern with 
low pressure in the eastern Gulf of Mexico and a western Atlantic
ridge to our east. With that, a squeeze play between these 
systems will result in above normal rain chances through the 
period, but the best chance for prolonged rainfall appears to be 
tonight and Tuesday morning. High temperatures will vary from the
lower 80s, to the mid and upper 80s with overnight lows in the 
lower 70s in heavy downpours to the upper 70s with the absence of 
rainfall. Regardless, considerable cloudiness with prevail through
this time frame, with breezy to windy conditions this afternoon 
through Tuesday. 

&&

.LONG TERM...(Thursday through Sunday)
Despite differences in the medium range guidance on the location
and intensity of lower pressure in the western Caribbean Sea or 
the Gulf of Mexico, copious amounts of moisture, spells of low 
level confluence and episodes of large scale ascent will prompt 
well above normal rain chances through at least Saturday, with 
some drier air perhaps filtering in Saturday night and Sunday. 
However, there is still plenty of forecast uncertainty so please 
stay tuned to the latest updates.

&&

.MARINE...
A gradual wind surge will overspread our marine district from east
to west, hence, a Small Craft Advisory is in effect for increasing
winds on all Keys coastal waters except the outer waters of
Mainland Monroe and the waters in and around Dry Tortugas.
However, another pronounced surge can be expected tonight when a
Small Craft Advisory will be required on our entire marine
district. Fresh to strong winds will prevail for most of Tuesday,
with winds gradually slackening Tuesday night through Wednesday
night. Thereafter, above normal uncertainty on wind speeds due to
the location and intensity of lower pressure to the south and 
west. Hence, please stay tuned for the latest coastal water 
package from your National Weather Service right here in Key West.

&&

.AVIATION...
A few light showers are possible this morning along the island 
chain. However, the higher probability of sub-VFR conditions is 
expected later this morning and early this afternoon. Have tempoed 
that possibility for those times at both island terminals, along 
with a VCSH from around sunrise onward. Expect a persistent east to 
southeast breeze near 15 knots through the day, with occasional 
gusts around 20 knots. 

&&

.CLIMATE...
In 1901, the daily record low temperature of 68 degrees was 
recorded in Key West. Temperature records date back to 1872. 

&&

.PRELIMINARY POINT TEMPS/POPS...
Key West 84 73 83 77 / 50 80 60 50 
Marathon 87 73 85 77 / 50 80 60 50 

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...Small Craft Advisory for GMZ031-032-035-042>044-052>055-072>075.

&&

$$

Public/Marine/Fire...APA
Aviation/Nowcasts....04

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