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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

                            
000
FXUS62 KKEY 110927
AFDKEY

Area Forecast Discussion...Updated
National Weather Service Key West FL 
409 AM EST Sun Nov 11 2018

UPDATED AVIATION SECTION

.DISCUSSION...
Isolated showers were present over the Straits of Florida, with
another batch moving southwest through Miami-Dade. The latter
batch appeared to be associated with a shallow impulse rounding
the eastern periphery of the Gulf ridge. Otherwise temperatures
were steady in the upper 70s to near 80, and dewpoints 72-74F.
Northeast to east winds were near 5 mph over the islands, and
running 10 to 13 knots along the reef. 

A cold front was noted over central Florida, continuing to slip
southward. High pressure was centered over the central
Appalachians, ridging into the northern Gulf. 

For today, Veterans Day, through tonight, high pressure will push
to the Mid Atlantic coast, and bridge the decaying frontal
boundary. Winds will turn easterly by this evening. Mostly shallow
showers will pass southwest near the Keys today, and there may be
some narrow cumulus convergence lines streaming west-southwest off
the island chain. Isolated showers are expected through tonight.

Monday through Tuesday, high pressure surface and aloft shifts 
entirely into the western Atlantic with a deep positive tilt 
trough moving into the central U.S. Surface winds will gradually 
veer, and while the profile is favorable similar to warm 
advection, significant dry air aloft (precipitable water dipping 
below 1.4 inches) may temporarily shut off shower production after
Monday morning.

Tuesday night through Thursday, guidance remains in difference but
has mroe clearly indicated a much slower front/trough passage
through the Keys; well later than the Wednesday morning passage 
earlier advertized. Thus, significant adjustment was made to
reduce winds mid-week although instability and moisture appear
adequate for chance pops. Guidance differs on whether the midweek
front moves through, or holds back in the eastern Gulf considering
the mean trough axis barely moves out of the central Plains.
Temperatures were also bumped up a category with the unfortunate
postponement of the front, poised to bring near-normal
temperatures to the Keys. 

Thursday night through Saturday, the one aspect guidance does
agree on is a second front, associated with the final eastward
translation of the mean trough into the Mississippi Valley. Chance
pops were maintained although the confidence of defined rainfall
areas remains low. Temperatures were lowered slightly for
Saturday.

&&

.MARINE...
Northeast to east winds will increase briefly over the western
waters before lulling slightly in the late afternoon, and
generally gradually increase elsewhere. Tonight, some small craft
exercise caution headlines will be likely especially over the
offshore Gulf, Straits and Hawk Channel as strong high pressure
over the mid Atlantic coast slides eastward into the Atlantic. 
Mostly moderate to occasionally fresh east winds Monday will
becoming southeast to south Monday night and Tuesday, and
gradually slacken as a front approaches the Keys from the Gulf of
Mexico. The cold front passage may take place later than
originally predicted, later Wednesday or early Tuesday. At least
caution headline winds and some small craft advisory level winds
and seas may occur, mostly over the Straits and offshore Gulf 
waters.

&&

.AVIATION...Updated 06Z Terminal Forecast Discussion: 

VFR conditions will prevail at both KEYW and KMTH terminals with 
cloud cover limited to SCT at or about FL020. Terminals will see 
light northeast become east northeast after 11/12Z and remain less 
than 10 knots. Possible VCSH at MTH until noon for showers moving 
off the mainland.

&&

.CLIMATE...

On this date in 1980, 22.75" fell when Tropical Storm / Hurricane 
Jeanne was stalled several hundred miles west of Key West. This was 
the wettest day ever recorded in Key West. Key West precipitation 
records date back to 1871.

&&

.PRELIMINARY POINT TEMPS/POPS...
Key West  85  78  85  78 / 20 20 20 30 
Marathon  85  78  85  78 / 20 20 20 30 

&&

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

$$

Public/Marine/Fire...JR
Aviation/Nowcasts....Chesser

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