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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

FXUS62 KKEY 212003

Area Forecast Discussion
National Weather Service Key West FL
303 PM EST Wed Feb 21 2018

.DISCUSSION...In the middle and upper levels(700-200 mb), latest
available satelitte imagery overlaid with model streamline
analysis as of 200 pm, depict a positively tilted longwave polar 
trough ensconced over the Western CONUS with its axis from
Saskatchewan down to Southern California, with an unusually 
strong middle and upper ridging pattern in place across the 
Eastern two thirds of the CONUS, with the center of strong middle 
and upper high pressure located over the Western Atlantic near 32 
North 73 West, or halfway between Bermuda and the Carolinas.

At the surface and in the lower to middle levels, (Surface to 700
mb), latest satelitte imagery overlaid with marine and land
observations and analysis as of 200 pm, detail the center of a 
very strong 1033 mb plus high pressure system near 32 North 60 
West, with its attendant axis extending west southwestward into 
the Carolina/Georgia Low Country retaining near 1030 mb pressure.

.CURRENTLY...As of 200 pm, skies are mostly sunny across the Keys
Island Chain and surrounding waters. Temperatures have reached the
lower to mid 80s across the islands with dewpoints around 70 
degrees. More typical of April. Radar only detects non precip
echoes attm. C-man stations along the Florida Reef are buzzing
near 20 knots with gusts actually between 23 and 28 knots. Free Ships
on the water are registering solid 20 to 25 knots. Smith Shoal
Light in the cooler waters is only 15 to 20 knots. 

.SHORT TERM...Tonight thru Monday, excellent weather for
landlubbers continues with steady state ridging positioned from
the West Central Atlantic to across the Southeastern United States
tonight through Friday, then slowly weaken in place Friday night
through Sunday. The ridge will gradually shift southwards to 
across Florida Sunday night through Monday. Latest model forecast
soundings, only the available GFS, continues to indicate a slight
moistening of the boundary layer late tonight and Thursday
morning continuing thru Thursday evening, with PWAT between 1.25 
to 1.50 inches. Given good late night flux and strong convergence,
will maintain 20 pops tonight, and 30 percent for Thursday, with
20 percent for Thursday evening. The ongoing forecast already has
this covered. Mid levels dry out a bit with PWAT at 1.25 inches or
less for Friday thru Monday, but given the strong convergence,
will maintain dime pops all the way thru this period. But any of
these brief small fast moving showers will deliver trace amounts
of rain and will be evasive. Temperatures each day will reach the
lower to mid 80s with low temperatures in the lower to mid 70s.
Tonight low max will likely tie for the max low for the date, 
which is 76 degrees for both KEY AND MTH. 

.Extended...Monday night thru Wednesday...Surface ridging across
the Florida Peninsula will gradually weaken thru the period,
resulting in lighter surface winds. Expect mostly clear skies with
only a 10 percent chance of showers. Would remove the showers if
lowest boundary layer levels would dry out below 1.00 inches 
PWAT, but still not the case attm. 


.MARINE...SCA conditions likely across Hawk Channel and the
Florida Straits through tomorrow afternoon, before weakening to
SCEC by tomorrow night thru Friday Night for these waters. SCEC
conditions likely across the shallower Florida Bay and nearshore
Gulf waters north of the Middle and Lower Keys, as well as over
the cooler Offshore Gulf waters thru tomorrow night. No headlines
or advisories in place for the weekend and after attm.


.AVIATION...VFR conditions will prevail at the island terminals
this evening. With that said, very brief high MVFR conditions 
will be possible due to isolated weak passing showers. Surface 
winds will be out of the east near 15 knots with gusts of 20 to 25
knots, decrease a little bit through the overnight period


GM...Small Craft Advisory tonight for GMZ042>044-052>055-072>075.




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