Area Forecast Discussion
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FXUS62 KKEY 250900

Area Forecast Discussion
National Weather Service Key West FL
500 AM EDT Tue Oct 25 2016

.DISCUSSION...A deep mean layered ridge is centered over the
Mississippi River Valley, supporting a surface high which sprawls
from Manitoba to the Appalachians. Meanwhile, the subtropical branch
of the jet stream has buckled across the Gulf of Mexico and also east
of the Bahamas. Aside from cloud cover, these ripples aloft have not
kinked any lower tropospheric mass fields. Satellite imagery
highlights the extensive mid-upper level cloud layers to our west.
Within breaks of the cooler cloud tops, lower level stratocumulus is
moving west southwest through the Straits of Florida. Aside from a
few sprinkles within the most intact cells, the KBYX radar is mostly
free of echoes. Temperatures are in the mid 70s with dewpoints in the
mid 60s. Northeast winds average 15 to 20 knots across the marine

.FORECAST...Today through Wednesday will feature strong east-
northeast breezes (at times gusting to 25 to 30 mph across the island
chain), increased cloud cover, temperatures in the lower to mid 80s
each afternoon, and overnight lows in the mid 70s. Rain chances will
be slim due to the reduced fuel content through the boundary layer
and the significant inhibition below 800 mb. The stable pattern will
be due to the consolidation of ridging partners across the
Southeastern United States. Sensible weather changes will occur
Wednesday night and Thursday. The buckled subtropical jet stream will
phase Wednesday night over the Yucatan Channel and the Bay of
Campeche. The upper levels will provide favorable venting aloft,
meanwhile, 925-700 mb wind vectors indicate greater than 30 knots of
low level easterly mass transport. What happens in between these two
layers will make all the difference. Moisture fields indicate the
tail end of a cold front will make a back door push through South
Florida and the Florida Keys on Thursday. Thereafter, the Florida
Keys will remain right on the cusp of deep tropical moisture to our
south, and maritime-modified continental to our north. Episodes of
frontogenesis along this boundary will be successful in producing
precipitation. The enhanced low level gradient and moisture will tend
to relax Saturday through Sunday, followed by more northeasterly
trajectories and lower theta-e infusions Sunday night and Monday.
Thus, rain chances will ramp up Wednesday night, peaking Thursday
through Friday, followed by decreasing chances thereafter. Rainfall
accumulations will hinge upon the amount of veering which can develop
within the level of non- divergence. Forecast reasoning has not
changed this cycle and no changes are needed.


.MARINE...A Small Craft Advisory is in effect for all coastal waters
of the Florida Keys. A high pressure system over the southeastern
United States will expand and intensify today through Wednesday.
Strong northeast to east breezes will develop today and tonight, and
persist through Saturday.


.AVIATION...VFR conditions are expected at the Key West and Marathon
Terminals today. Scattered and possibly briefly broken cloud bases
near FL050 are expected to lower, reaching near FL030 by midday
Tuesday. Northeast breezes 7 to 10 knots early this morning are
expected to increase shortly after sunrise to 10 to 13 knots with
occasional gusts near 20 knots.


Key West  84  75  85  75 / 10 10 10 30
Marathon  83  76  84  76 / 10 10 10 30


GM...Small Craft Advisory until 6 PM EDT this evening for GMZ031>035-



Data Collection......Fling

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