Area Forecast Discussion
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FXUS62 KKEY 270844

Area Forecast Discussion
National Weather Service Key West FL
444 AM EDT FRI MAY 27 2016

.DISCUSSION...In the middle and upper levels, (700-200 MB), the
latest available IR imagery overlaid with model streamline analysis
as of 3 am depict a split pattern over the Eastern United States with
developing ridging over the Middle Atlantic and Northeastern States,
and a trough over east of Florida centered over Andros Island but
encompassing the Southeastern United States including the entire
State of Florida, the Keys, all of the Bahamas and adjoining waters.

At the surface and in the lower to middle levels, (Surface to 700
MB), a surface ridge extends from near Bermuda southwest to the
Carolina Piedmont. South of that, an area of low pressure is
developing near 26 North 74 West. Last evenings 00z sounding at Key
West represented a fairly dry lower to mid troposphere with PWAT at
only .91 inches, but has which has moistened since, with increasing
dry air with strong northerlies above that, which is in association
with the cyclonic flow associated with the aforementioned middle and
upper level trough.

.CURRENTLY...As of 3 am. skies across the Keys island chain are
partly cloudy. Temperatures across the islands are in the upper 70s,
with dewpoints around 70. Winds along the Florida Reef are east to
southeast 10 to 15 knots...and east near 10 knots over the islands.
KBYX radar detects isolated showers across all waters surrounding
the Florida Keys.

.SHORT TERM...Today through Sunday night, Middle and Upper Low
pressure is expected to work in tandem with surface low pressure east
of the Northern Bahamas, resulting in development of a subtropical or
tropical system well East of the Northern Bahamas. This system is
progged by the NHC to develop into either a subtropical or
tropical cyclone and move northwest, reaching the South Carolina low
country by Sunday. Locally, this will keep the Keys beneath deeper
cyclonic air with lots of dry air in the middle levels. As a result,
latest available model forecast soundings are indicating that PWAT
values will remain low, at 1.00-1.25 today and tonight, rising a
little to between 1.25 and 1.50 for Saturday and Saturday night, then
to between 1.50 and 1.75 for Sunday and Sunday night. Given a weak
surface pressure pattern developing tonight and continuing through
Memorial Day, just isolated chances for showers and thunderstorms
will be left in the grids for today through Saturday. A deeper
moisture profile supports better mesoscale shower process
development, so low chances for showers with isolated thunderstorms
will be inserted into the grids across the Keys for the Saturday
Night through Sunday Night periods.


.LONG TERM...Memorial Day thru Thursday, The Florida Keys will
experience more typical weather as we celebrate the Holiday and
enter the first days of meteorological summer, as well as the
beginning of June and now what we can conclusively now say will be
the first full week of the new wet season as well. A typical weaker,
broad surface ridging pattern across the Florida Peninsula will be
accompanied by slightly drier air in the middle levels. This will
work against favorable light to gentle northeast to easterlies
which allow for mature cumulus/towering cumulus cloud line
development. So will advertise a near climo 20 percent pop for these
periods for now, but if forecast soundings begin to illustrate more
available moisture, then rain chances will likely be increased up
into the lower to middle chance ranges for the week.


.MARINE...Today through tuesday night, a weaker pressure pattern will
result in gentle northeast to east winds, light at times. No
headlines or advisories expected but mariners close to shore along
the Keys should look out for the possible formation of waterspouts,
which tend to form along the edge of long dark flat cloud bases.


.AVIATION...Until 00z/28th, the best chance for a sub vfr encounter will
be early this morning, otherwise, vfr conditions can be expected at the
Key West and Marathon terminals. Mostly east winds of 10 knots or less can
be anticipated.


.CLIMATE...In 1984, the daily record rainfall of 2.95 inches was recorded
in Key West. Rainfall records have been kept since 1871.


Key West  87  78  88  78 / 20 20 20 30
Marathon  89  78  90  78 / 20 20 20 30





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