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FXUS62 KKEY 282050

Area Forecast Discussion
National Weather Service Key West FL
350 PM EST Tue Jan 28 2020

Afternoon temperatures have reached the mid to upper 70s across
the Florida Keys amid gentle north to northeast breezes. GOES-East
visible satellite imagery depicts mostly sunny skies with Key West
radar picking up only non-meteorological echoes. Showers over the
Straits departed our waters to the south earlier this afternoon as
the influence of the surface trough wanes.

Concerning the short term forecast (through Thursday night), the
synoptic pattern will remain highly progressive with depressed 500
mb heights allowing shortwave troughs to ripple through the largely
zonal flow aloft. This pattern will bring the next weak cold front
through the area tomorrow night into Thursday morning, ushering in
a relatively brief period of showery weather. Temperatures will
not fall much at all behind the front, but humidity will dip down
a bit due to the north wind. High temperatures will mainly be in
the upper 70s with lows falling into the mid to upper 60s.

More substantial changes arrive for the long term forecast
(Friday through Monday night). The atmosphere will quickly become
saturated again on Friday as an impressive cyclonically veering
vertical profile becomes established in the model soundings. Low-
level southerly flow should allow for a Cuban shadow effect during
the day Friday, limiting PoPs and likely preventing thunderstorm
formation until the evening. By Friday night the cap should be
sufficiently eroded as vertical flow becomes more unidirectional
from the southwest to west. This should lead to a period of
elevated PoPs Friday night and Saturday with a more potent cold
front likely clearing the region by Saturday night. Decided to go
ahead and add slight chance thunder for those periods, considering
the enhanced lift with the trough, ample deep moisture, and
modest instability (ML CAPE ~500 J/kg). A respectable surge of
northwest to northerly winds can be anticipated with the front
Saturday through Sunday morning, but there is not a lot of cold
air to speak of. This is due to the source region of the air mass
originating in the northern Plains with the coldest air remaining
locked far north in the Arctic. The result will be temperatures in
the lower 60s for lows and lower to mid 70s for highs from Saturday
night through Monday (with a comfortable fall in dew points into
the 50s). The pattern looks to remain progressive to begin next
week with moderation likely.


No watches, warnings, or advisories are currently in effect for
the coastal waters of the Florida Keys. Gentle to light breezes
will generally prevail due to a weak pressure pattern through
Friday night (the exception being Wednesday night and Thursday
morning when a weak cold front will freshen breezes to moderate
strength). The next substantial cold front will arrive Saturday
or Saturday evening, likely bringing a fresh blow of northwest to
north winds through Sunday morning. Breezes will likely slacken to
start next week.


Areas of strato-cu remain in the vicinity of the Florida Keys but
are struggling to hold together as they move towards the island
terminals. VFR conditions expected with light and variable winds
from the NW to NE through the period.


On this date in 1940, the daily record cold high temperature of
52 degrees was recorded in Key West. Temperature records date back
to 1872.


Key West  68  78  69  78 / -  -  50 20
Marathon  68  80  68  79 / -  -  40 20





Data Collection......BT

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