Area Forecast Discussion
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FXUS62 KKEY 241331

Area Forecast Discussion
National Weather Service Key West FL
931 AM EDT Fri Mar 24 2017

.DISCUSSION...In the middle to upper level(700-200 mb), latest
available model streamline analysis overlaid on top of satelitte
imagery depicts a deep low pressure system pushing eastwards attm
near, over the Oklahoma Panhandle. This system is embedded within a
split flow over the Western CONUS. Downstream of that, a deep and
warm middle and upper level ridge bulges northward to Ontario from
the Central and Western Gulf of Mexico. But more pertinent, to
Keys weather, there is a well defined north to south oriented (at
500 mb) trough axis positioned from near 74 West 30 North south
southwest to over the Central Bahamas to over Cuba thence into
the Western Caribbean Sea.

At the surface and in the lower to middle levels(Surface to 700
mb), Latest satelitte imagery overlaid with marine and land
surface observations and analysis as of 900 am, details the
center of a 1036 mb strong surface anticyclone was positioned well
east of the Delmarva Peninsula. Well south of that, a nearly
stationary frontal boundary is analyzed from near New Orleans
southeast across the Gulf and bisecting the Florida Keys to Andros
Island and then east of Cat Island. As a result, the 12Z sounding
illustrated a fresh NE to E flow from off the surface up to 500,
then backing and becoming strong above that. The lower to middle
troposphere was only slightly moist with PWAT at 1.23 inches.

.CURRENTLY...As of 900 am, skies are partly cloudy across the
islands and all surrounding waters with Key West radar detecting
isolated showers impacting the Keys and shallower waters to the
north, but scattered showers are upstream of the Keys, moving
westward near 20 knots across the Atlantic waters and over the
Gulf Stream. Temperatures over the islands are in the lower to mid
70s with dewpoints in the mid to upper 60s. C-man showers are
recording sustained east winds between 20 and 25 knots and gusty,
near 20 knots in Florida Bay, but ship reports are suggesting
winds out in the straits may be sustained near 25 knots. Winds in
any of these showers will easily be gusting between 28 and 33

.SHORT TERM...Rest of today and this evening, The stalwart early
spring surface anticyclone positioned in the Western Atlantic,
well east of the Delmarva, will remain near 1035 mb a few hundred
miles east of Virginia Beach, sliding very slowly eastwards thru
this evening and overnight. The aforementioned axis of the 500 mb
trough, just east of the Keys will only move slowly away from the
area, but this feature in close proximity and the strong lower
level convergence generated by the aforementioned surface high
pressure, will help to generate widely scattered to scattered
showers upstream of the islands thru the balance of the day.
Despite latest available GFS, ECMWF forecast soundings
illustrating a slight decrease in lower level moisture in the
column thru the afternoon, expect that the near surface
convergence and air sea fluxes still justify maintaining low
chances for showers through the afternoon. This was already
incorporated in the inherited forecast, hence no changes will be
made on this cycle.


.MARINE...Given the aforementioned synoptic scenario, a SCA will
remain in place across all waters thru the afternoon. SCA
conditions seem likely across all waters tonight as well, with the
possible exception of the Florida Bay, where winds could be a few
knots lower but even that still seems a bit iffy at this point,
as decoupling affects are minimal.


VFR conditions will prevail at EYW and MTH today and tonight.
Sustained east winds of 20 to 25 knots expected from just off the
surface to about 3,000 feet.


On this date in Florida Keys weather history, in 1994, the high
temperature at Key West International Airport was 88 degrees. This
set the daily record for maximum temperature measured in Key West on
March 24th, a record which still stands 23 years later. Temperature
records at Key West date back to 1872.


GM...Small Craft Advisory continue today GMZ031>035-



Upper Air/Data Collection......Vickery

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