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FXUS62 KKEY 201334

Area Forecast Discussion
National Weather Service Key West FL
934 AM EDT Sun Oct 20 2019

.DISCUSSION...In the middle and upper levels(700-200 MB), latest
available satellite imagery overlaid with model streamline
analysis as of 900 am, depicts a developing full latitude trough
across the Western CONUS with a formidable middle and upper low
taking place over Northern Wyoming. Downstream of that, overall
low amplitude ridging is in place across much of the Great Lakes
and Eastern United States. To the south, an intensifying synoptic
scale middle and upper anticyclone is developing near 24N 86W, in
the SE Gulf of Mexico, with its attendant east to northeast
oriented ridge axis over the Florida Keys, Southern Florida and
the Northern Bahamas.

At the surface and in the lower to middle levels(Surface to 700
mb), latest available marine and land surface observations and
analysis as of 900 am, detail a 1020-1025 mb high pressure cell
centered over Northern New England. South of that, an area of Low
pressure, remnants of Nestor, located over the South Carolina Low
Country, trailing a weak frontal boundary southwards to across 
part of North Central Florida, with dewpoints in the 50s and lower
60s northwest of that point. Closer to the Keys, a weaker surface
ridge is presently moving from Western and Central Cuba and into 
International waters to the immediate north. As a result, the 12Z 
sounding at KEY exhibited a moderate to fresh still moist south to
southwest flow from off of the surface to about 750 mb, with 
columnar PWAT at 2.17 inches, very high, well above the 90% moving
average for Oct 20th as indicated at the SPCs sounding 
climatology page. 

.CURRENTLY...As of 900 am, skies are mostly sunny over the Keys
and immediate surrounding waters, but still partly to mostly
cloudy arcing from Western Florida Straits waters including
GMZ005-075 to GMZ034 out at the Dry Tortugas into GMZ033, the
waters 20 to 60 nm west of Mainland Monroe County. And radar does
still detect widely scattered showers and possibly a storm or two
lurking along the old boundary across the northwesternmost 
portions of GMZ033. Temperatures across the islands are already in
the lower to middle 80s with dewpoints in the upper 70s. C-man
stations along the Florida Reef generally running south to
southwest at 10 to 15 knots in most cases. 

.SHORT TERM...For the rest of today and this evening, as the
aforementioned surface ridging north of Cuba migrates northwards
through the afternoon local south to southwest winds will become
light to gentle. Then by this evening, the surface ridge should be
north of the islands. As such local winds will back into a
southeasterly direction, albeit light to gentle as well. Though
the profiles is quite moist this morning, drier air advecting in
from the deep and warm anticyclone positioned west of the Keys 
will begin filtering down into the middle levels. This will erode 
out the vestiges of the aforementioned boundary over GMZ033 by
later in the afternoon. Given the moisture remaining right near
the surface, will leave in a dime pop in the grids thru this
evening. The ongoing forecast has all of this covered. Other than
some minor griding adjustments, no changes on this cycle. 


.MARINE...Today thru this evening, Somewhat elevated seas over 
the Western Straits will continue to subside through the 
afternoon. As such, there are no headlines or advisories in place 
across all waters. Gentle to moderate south to southwest winds
will become light to gentle southeast winds on all waters by this


.AVIATION...VFR conditions are expected throughout the next 24
hours at the EYW and MTH terminals, thanks in part to a slow 
trend of the air mass becoming less moist and unstable. Most 
shower activity should steer clear of the island terminals, 
focusing mainly over the Straits and Gulf from southwest through 
northwest of Key West and beyond 10 miles out.

Otherwise, there will be a gradual wind shift at both terminals
late this afternoon or early this evening that will force a
reversal of traffic flow on the east-west runways. The westerly 
wind component today will become southeasterly by this evening.




Upper Air/Data Collection......NB

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