Area Forecast Discussion
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FXUS62 KKEY 241952

Area Forecast Discussion
National Weather Service Key West FL
352 PM EDT Mon Oct 24 2016

...Windy Week Ahead, With Higher Rain Chances After Wednesday...

Changes to Forecast -- We made some slight adjustments to both
digital and derived forecasts, mainly to delay higher rain/thunder

Current Situation and Analysis -- The stratocumulus deck which has
maintained prevailing cloud ceilings over middle and upper Keys
island communities today has eroded whilst migrating toward the
west-southwest, keeping lower Keys communities under plentiful
sunshine.  The atmosphere remains stable and dry aloft, with no
precipitation detected by Key West Doppler radar.  Currently, air
temperatures in the Keys are mainly in the lower 80s, with dewpoint
temperatures mostly in the mid 60s.  The air mass of continental
origin has modified during the last 48 hours.  However, pure
maritime tropical air remains far to the south over the Caribbean
Basin.  On the large scale, a deep layer mean anticyclone centered
over the Gulf of Mexico maintains deep ridging and subsidence over
the service area.

Prognostic Overview -- A high pressure area centered over the Deep
South is expected to intensify as it shifts over the southeastern
United States tonight through Tuesday night.  Meanwhile, pressures
likely will begin to fall over the northwestern Caribbean Sea thanks
to an approaching low-latitude, upper trough and jet streak.  As a
result of these developments, northeast/east gradient flow should
increase significantly during the Tuesday-Tuesday night time frame.
The strong low-level flow will persist, with some fluctuations,
through Sunday, resulting in robust upward fluxes of heat and
moisture from surrounding warm seas.  Near-surface equivalent
potential temperature will increase gradually during the next few
days, resulting in a progressively more moist and unstably
stratified atmosphere.  In addition, weather prediction models
suggest additional lowering of pressures over the northwestern
Caribbean during the Wednesday-Saturday time frame, which would
induce a confluent east-northeasterly flow favoring higher cloud
cover, rain, and thunderstorm chances across the Florida Keys and
adjacent coastal waters.  This reasoning is consistent with what has
been indicated for the last few forecast cycles.  Our changes with
this package mainly constitute tweaks to timing.  Some drying
seems probably by Sunday night or Monday as incoming trajectories
once again become rooted in continental air.

A Small Craft Advisory remains in effect for the Straits of Florida.
Small craft should exercise caution remains headlined for Hawk
Channel and the extreme southeastern Gulf of Mexico.  A high
pressure system over the southeastern United States will expand
and intensify tonight through Wednesday.  Strong northeast to east
breezes will develop Tuesday and Tuesday night, and persist through

Northeast winds near 10 kts and gusts to around 20 kts are expected
this afternoon at both KEYW and KMTH through 3 kft. A scattered to
broken stratocumulus deck around 4-5 kft will continue over KMTH
this afternoon, diffusing by early evening. Winds will drop to near
10 kts after sunset and pickup again Tuesday morning after sunrise.

Key West  73  82  75  83 / 10 10 10 10
Marathon  73  82  75  83 / 10 10 10 10

GM...Small Craft Advisory in effect for GMZ052-GMZ053-GMZ054-GMZ055-


Data Collection......Fling/Vickery

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