Area Forecast Discussion
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FXUS62 KKEY 210155

Area Forecast Discussion
National Weather Service Key West FL
955 PM EDT Sat Apr 20 2019

Dry and cooler conditions prevail across the Florida Keys on this
Saturday evening, in the wake of the strong cold front that moved
through Friday night. Satellite imagery depicts scattered
stratocumulus across the area, while radars show no precipitation.
Temperatures along the island chain are falling through the lower
70s, and winds on land are from the northwest at 10 to 15 mph.

Surface analysis depicts weak high pressure over the central Gulf
of Mexico. Aloft, the deep trough axis that pushed the front
through Friday night now extends southward from the central
Appalachians through Florida. GOES derived TPW imagery shows a
very dry airmass over the Keys area and upstream over the Gulf,
with estimated PW values well below one inch. The 00Z Key West
sounding also depicts a dry and stable airmass in place, with a
strong inversion based near 6000 feet, and a PW of 0.88 inches
which is near the 10th percentile for this time of year.

Overnight, expect partly cloudy skies to prevail, while a notably
dry and cool airmass for late April continues to filter into the
area. Lack of available moisture will preclude any chance of rain.
Lows by morning should drop into the upper 60s at most locations,
with mid 60s possible in the Upper Keys, while dewpoints dropping
into the upper 50s will feel very comfortable. The existing
forecast appears to be on track, and no updates are planned for
this evening.


Significant wave heights at the Pulley Ridge CDIP buoy, located
about 75 nm northwest of the Dry Tortugas, have dropped to 6.5
feet recently, and wave guidance shows that heights will continue
to drop steadily during the rest of the night. Based on this data,
will likely drop the Small Craft Advisory for seas across the
offshore Gulf waters and western Straits, replacing it with a
Small Craft Exercise Caution headline due to lingering west to
northwest swell generating seas of 4 to 6 feet during the rest of
the night. This swell and resulting wave heights will continue to
gradually subside on Sunday. Otherwise, no significant changes are
planned for the late evening forecast issuance.


VFR conditions will prevail overnight and Sunday at the EYW and
MTH island terminals. There will be periods of ceilings near 4000
feet overnight, then mostly clear skies are expected Sunday with
just few to scattered clouds. NW to N surface winds of 9 to 13
knots this evening will decrease slightly late tonight into


GM...Small Craft Advisory for GMZ033-034-054-055-074-075.



Data Collection..........SD

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