Area Forecast Discussion
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FXUS62 KKEY 200901

Area Forecast Discussion
National Weather Service Key West FL
401 AM EST Mon Feb 20 2017

Under partly cloudy skies with gentle to moderate north to
northeast breezes, temperatures in the Florida Keys are in the
upper 60s to lower 70s. There is no precipitation in the Keys
service area early this morning.

High surface pressure will be extending southward down the Florida
peninsula today through Tuesday as an amplified but narrow upper
ridge slides eastward across the eastern portion of the country
and the eastern Gulf. A mid level trough will deepen and is
expected to cutoff over the Red River Valley by early Tuesday. The
associated surface low is now expected to follow suit off the
northwestern Gulf coast, then swing towards South Florida and the
Keys Wednesday through Thursday. Confidence in the exact timing
and strength of the entire system...and hence precise sensible
weather expectations...remains very low. The ECMWF is not behaving
nicely from run-to-run. Whereas a recent solution showed a very
weak surface trough shunted by the lingering high pressure
extending across the western North Atlantic, the latest solution
swings a stronger and more complex surface low more quickly
towards the Keys for the middle of the week when compared to the
GFS. The GFS in itself has not been very consistent with the
strength and location of what should be a stacked cyclonic system.
Its latest solution is weaker and slightly north of the most
recent ECMWF. Due to the model-to- model and temporal
discrepancies, am deciding to continue with the elevated
probability of precipitation for Wednesday through Thursday,
accompanied by the possibility of thunderstorms. Due to the very
high uncertainty of this system, expect at least some measure of
adjustments to the sensible weather elements over the next couple
of days. Suffice it to say, unsettled conditions are a fair bet
especially for Wednesday through Thursday.

Looking beyond Thursday, a low amplitude mid level ridge swinging
through the eastern Gulf followed by broad high surface pressure
dropping through the Mississippi Valley should sweep the unsettled
pattern well to our east. Expect a low chance of showers for the
late periods with temperatures remaining several degrees above the
seasonal average.


Gentle to moderate north to northeast breezes will turn more
easterly through late this evening and into Tuesday as high
surface pressure settles across Florida and then shifts eastward.
There is a high degree of uncertainty for the middle portion of
the week as far as wind speeds and direction are concerned, thanks
to the scenario described above. Don`t be surprised by
modifications to the wind and sea details over the next few
forecast cycles, but expect at least good coverage of showers
accompanied by at least a few thunderstorms Wednesday through
Thursday across all waters surrounding the Florida Keys.


VFR conditions are expected at EYW and MTH terminals today. North to
northeast winds of 10 knots or less will turn from the east later
this morning and into the afternoon.


On this date in Keys weather history, in 1984, the daily record high
temperature of 85F was recorded. Temperature records for Key West
date back to 1872.


Key West  81  70  80  69 / -  -  -  20
Marathon  82  72  80  70 / -  -  -  20





Data Collection......Chesser

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