Area Forecast Discussion
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FXUS62 KKEY 140830

Area Forecast Discussion
National Weather Service Key West FL
330 AM EST Thu Dec 14 2017

A radiational cooling event is underway across the island chain,
as IR imagery reveals cloudless skies, ASCAT shows calm to light
and variable winds, and surface analysis indicates a high pressure
center located across the southern Florida peninsula. Dew points
range from the mid 40s to mid 50s, and temperatures ranging from
48 in Big Pine Key, to 50 in Card Sound, to 53 at NWS Key West,
to 59 in Key Largo and Cudjoe Key. On a larger scale, a broad low
pressure trough is in place across the Upper Midwest and Northeast
US, and swinging a series of cold fronts across the central and
eastern CONUS.

Temperatures will have the opportunity to dip a little lower in
the immediate future before calm surface winds become light. The
daily cold record for December 14th is 50 degrees in Key West,
and this record appears marginally safe unless dew points from
the 900 mb level are able to waft to the surface. A high pressure
cell will linger across South Florida today and tonight before
sliding into the western Atlantic Friday afternoon. Expect a
gradual rise atmospheric heights as an upper level ridge builds
across the eastern Caribbean and Western Atlantic - acting to
increase our dew points back into the 60s come Friday. Another
radiational cooling event is likely tonight as winds become calm,
but increasing low level moisture will keep minimum temperatures
5-10 degrees warmer than current observations.


The upper level pattern will favor cold, cyclonic flow (with a
series of clipper systems) translating across the Central and
Northeast US, and neutral to warm anticyclonic flow across the
Caribbean and southern Florida Peninsula Friday night through
Wednesday night. Temperatures and humidity will continue their
upward climb through the weekend, with dew points inching back
into the 70s Sunday night/Monday. Returning easterly breezes will
bring an increase in cloud cover and isolated showers, though
overall rain chances remain very low through the 7-day forecast.
Major model guidance is hinting at a possible cold front late next
week as a broad upper level ridge shifts southwest to the Yucatan


No watches, warnings, or advisories are in place across the
coastal waters to the Florida Keys. Pleasant marine conditions are
expected to continue through Saturday as high pressure lingers
near the Keys, creating gentle easterly breezes. A high pressure
cell will build across the Southeastern US, causing moderate to
freshening breezes Saturday night through Monday.


Until 12z/15th, VFR conditions will prevail at the Key West and
Marathon terminals. Calm winds will become northeast to east at
around 5 knots by late this morning before becoming light and
variable tonight.


In 2010, the daily record low temperature of 50 degrees was last
recorded in Key West. Temperature records have been kept since 1872.


Key West  70  57  74  63 / -  -  -  -
Marathon  71  57  75  63 / -  -  -  -





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