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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

FXUS62 KKEY 100855

Area Forecast Discussion
National Weather Service Key West FL
355 AM EST Sat Nov 10 2018

Isolated showers have persisted over the western Straits,
otherwise skies were mostly clear with temperatures in the mid to
upper 70s, and dewpoints in the lower 70s. 

The Keys will be in a weak pressure gradient today with a narrow
ridge across the western Atlantic. A cold front currently
progressing through Apalachee Bay into the central Gulf will
become more diffuse as strong high pressure across the middle
Mississippi Valley moves eastward to the Mid Atlantic coast by
late Sunday. While the best gradient will be to the north of the
Keys, a brief northeast to east surge can be expected beginning
late tonight. Shallow moisture may allow some cumulus lines and
local showers over the islands while the northeast to east flow
remains light this afternoon, otherwise more sparadic, isolated
showers moving quickly west and southwest will be the main
rainfall mechanism by late tonight.

A stronger cold front is expected to sweep through the Gulf from
late Monday through Tuesday night, with passage through the Keys
possibly during the early morning hours Wednesday. A brief period
of shallow moist isentropic lift occurs Tuesday, before flow
fields become a big chaotic as high pressure attempts to bridge
across the frontal boundary as it slows Tuesday night and
Wednesday. Even as the surface boundary passes, weak isentropic 
lift remains aloft, mainly 315-320K surfaces. Thus considerable
cloudiness and some sprinkles/light rain showers may continue into

Thursday through Friday, the combination of shallow moist
northeast to east flow with strong high pressure to the north and
deep troughing across the Gulf thorugh the Florida panhandle could
spell unsettled weather. Initially, mid level ridging keeps any
significant isentropic lift at bay, until later Thursday night and
Friday. Raised rain chances a bit for the end of the week. 


After a period of light northeast to east winds today and
onshore seabreezes along the northern Florida Bay, high pressure
sliding across the eastern U.S. will cause a brief surge in
easterly winds late tonight especially for the Gulf waters beyond
5 fathoms, and the open Straits. It is possible a brief period of
caution winds 15 to 19 knots may occur over the open Gulf. Mostly
moderate east winds, occasionally fresh over the open Straits and
Hawk Channel, will weaken later Tuesday in advance of an
approaching cold front. Small Craft Advisory conditions may occur
after the passage of the cold front Wednesday morning.  


.AVIATION...06Z Terminal Forecast Discussion: 

VFR conditions will prevail at both KEYW and KMTH terminals with 
cloud cover limited to FEW to SCT. Terminals will see light and 
variable winds become northeast and remain less than 10 knots before 
becoming light and variable again after 11/00Z.  



On this date in 1987, the daily record high temperature of 87F was 
last recorded. Key West temperature records date back to 1872.


Key West  85  77  84  77 / 20 20 20 20 
Marathon  86  76  85  77 / 20 20 20 20 





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