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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

FXUS62 KKEY 102010

Area Forecast Discussion
National Weather Service Key West FL
310 PM EST Sat Nov 10 2018

.DISCUSSION...In the middle and upper levels( 700-200 mb), latest
available GOES-R satellite imagery overlaid with model streamline
analysis as of 200 pm depict zonal flow over the Middle and 
Eastern portions of the CONUS, but the next NE to SW oriented 
positively tilted trough is developing from Manitoba SW to Utah. 
Across the Southern CONUS, South Florida and the Florida Keys are
beneath the northern periphery of an expansive anticyclone 
centered across Northern Central America. 

At the surface and in the lower to mid levels(Surface to 700 mb),
latest available GOES-R satellite imagery overlaid with marine 
and land surface observations and surface analysis, as of 200 pm,
detail a cold front extending south southwest to across Northern 
Florida and into the SW Gulf from rapidly intensifying low 
pressure east of Southern Maine.

.CURRENTLY...As of 200 pm, skies are mostly sunny across the 
islands and adjoining waters. Radar does not detect any showers
anywhere in the service area attm. Temperatures across the 
islands have reached the lower to mid 80s with dewpoints in the
upper 60s to lower 70s. C-man stations along the Florida Reef are
recording North to Northeast winds near 10 knots, with island 
platforms at 5 to 10 mph. 

.SHORT TERM...Tonight thru Tuesday Night, including Veterans Day.
Looks as if a continuation of above normal temperatures and
humidity values will continue thru the rest of the weekend and the
first half of next week. On a more positive note, as a strong 
early season anticyclone of arctic origins continues to move 
towards the Middle-Atlantic coast tonight thru tomorrow evening, 
local breezes will kick up a notch for our Veterans Day tomorrow. 
But the near breezy to breezy conditions will add a bit more 
comfort to these muggy conditions Veterans Day through Monday 
despite dewpoints remaining in the 70s. Then local winds will drop
down again by Monday evening, with gentle to moderate breezes 
expected through Tuesday evening. This will occur as a powerful 
cold front moves across the breadth of the Gulf towards South 
Florida and the Keys due to the eastward migration of the 
aforementioned deep polar trough (first paragraph). 

As local winds drop off ahead of this approaching front they will
veer around beginning Monday night. Latest forecast soundings are
transporting a little more moisture Monday Night thru Tuesday 
night, but dynamics are fairly weak. Hence the pre-frontal 12 hour
pops we have advertised, 30%, for these 3 periods, are not that 
bullish, but still slightly below guidance as well. Latest 12Z 
GFS brings the center of this next cold high pressure system of 
arctic origins, behind the front, southwards by the middle of the 
week, with a near 1040 mb near NE Arkansas by 18Z Wednesday. As 
such local winds could be increasing late Tuesday night. Given 
strong cool thickness advection thinking that the winds could 
increase a bit earlier when this air moves across the still very 
warm Gulf waters.

Extended, Wednesday through Saturday, Surface frontal system is
still progged to slow down as it gets near the Keys, but there are
timing differences remaining between both the 12Z GFS and ECMWF
runs. It still does appear that the surface boundary may return
back to the north again after it pushes south towards South
Florida and the Keys. As such, will maintain a slight chance for
showers for Wednesday night thru Saturday. Have maintained
elevated winds for Wednesday Day thru Thursday, but its possible
breezy conditions could still be in place across the Keys Thursday
Night thru the weekend, given the strength of the ridging. Another
factor which could impact the local MSLP gradient would be a
strengthening hybrid system several hundred miles east of the
Bahamas during Wednesday. For now daytime highs and overnight 
lows for the extended are near the climatological normals.


.MARINE...SCEC headlines are likely across portions of the Key
waters Sunday thru Monday afternoon before our local winds and
seas let down Monday night thru Tuesday evening. Thereafter, a
very strong arctic high moving east across the MidSouth and
Eastern United States will result in developing SCA conditions
across portions of the waters beginning late Tuesday Night lasting 
thru Thursday, with SCEC conditions remaining Thursday Night.


.AVIATION...VFR conditions expected at both the KEYW and KMTH
island terminals tonight. Surface winds from 040 degrees aoa 8-10
knots will increase to between 11 and 13 knots and gusty at both 
terminals late.


Key West 77 84 77 84 / 10 20 20 20 
Marathon 76 85 77 84 / 10 20 20 20 




Upper Air/Data Collection......BT

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