Area Forecast Discussion
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FXUS62 KKEY 141100

Area Forecast Discussion
National Weather Service Key West FL
600 AM EST Sat Dec 14 2019

Under variably cloudy skies and increasing southwest winds,
temperatures have risen into the mid to upper 70s along the island
chain overnight. Meanwhile, local radars are not detecting any
precipitation echoes. On our marine district, winds are southwest
to west ranging from 6 knots at Carysfort Reef Light to 15 knots
at both Alligator Reef Light and Sand Key Light.

.SHORT TERM...(Today through Monday night)
A deep and negatively tilted mid and upper level short wave trough
extending from the upper Mid West States southeastward and down
the Sunshine State early this morning, will lift out into the
north Atlantic Ocean today. With that, mid and upper level ascent
early this morning will quickly be followed by subsidence aloft
across our region. However, a lagging, albeit weak cold
front/trough in the Southeast Gulf of Mexico will cross our entire
area by this evening. Given ample moisture below 700 mb, weak
upglide and low level confluence, a few narrow broken bands of
showers are expected to pass through the island chain this
afternoon. Hence, low chance pops will be inserted for today,
with no measurable rainfall expected later this evening through
Sunday night. A freshening northeast to east confluent flow will
prompt isolated 10 to 20 percent pops to be retained for the
balance of this forecast period. Above normal temperatures today
will return to near average tonight and Sunday, before moderating
slightly Sunday night through Monday night.


.LONG TERM...(Tuesday through Friday)
A deep mid and upper level trough over the nations midsection will
move quickly eastward into the Eastern United State, and southward
into the Gulf of Mexico on Wednesday before flattening out late
Wednesday into Thursday. With that, a formidable cold front will
likely push through our entire region by late Wednesday, before
stalling over the Central Bahamas to across the archipelago of
Cuba Wednesday night and Thursday. Since most of the ascent aloft
will lag well behind the cold front, only low chance pops seem
reasonable on Wednesday. But until then, limited moisture, the
Cuban shadow and a decelerating low level flow may prompt only
isolated 10 to 20 percent pops for Tuesday and Tuesday night. In
wake of the cold front, a strong northeast to east trajectory may
pose a chance of showers late Thursday into Friday. Well above
normal temperatures Tuesday will finally be slightly below normal
beginning Thursday.


Gentle to moderate southwest to west winds will become west near
15 knots on most Keys coastal waters today, before turning
northwest and then north behind a weak cold front passing through
our entire region this evening. For the balance of this weekend
and early next week, winds will freshen as high pressure builds
over the Southeast United States and slides into the western
Atlantic Ocean. Furthermore, a Small Craft Should Exercise Caution
and perhaps a Small Craft Advisory may be necessary Sunday night
into early Monday morning. Thereafter, winds will slacken
appreciably ahead of a cold front which appears likely to pass
through our entire marine district on Wednesday. With this cold
front, the probability is high that a Small Craft Advisory will be
required on all Keys coastal waters.


VFR conditions will prevail at both terminals. Isolated VCSH
possible this morning as a weak frontal system moves slowly through
the Keys Saturday. SW winds will be near 10 knots with gusts near 20
knots. Winds behind the front will veer to the NW as gusts abate and
then become N overnight. Lacking confidence in formation dynamics
for MVFR ceilings behind the front Saturday night.


In 2010, the daily record low temperature of 50 degrees was last
recorded in Key West. Temperature records date back to 1872.


Key West  83  72  79  75 / 30 10 -  10
Marathon  86  70  81  75 / 30 10 -  -





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