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Area Forecast Discussion (AFD)

Issued by Key West, FL (KEY)

FXUS62 KKEY 202040

Area Forecast Discussion
National Weather Service Key West FL
440 PM EDT Fri Apr 20 2018

A weak pressure gradient under sunny skies has lead to light to
gentle breezes across the Florida Keys and surrounding coastal
waters. Temperatures are currently in the upper 70s to low 80s.
Dew points are generally in the upper 60s. KBYX is free of any
precip echos. 

A weak boundary in Central Florida will continue limping down the
Florida Peninsula, stalling north of the Florida Keys tonight.
Current satellite/radar appearance of the boundary remains devoid
of showers and an air mass change is not expected locally. After 
09z and beyond, fcst soundings indicate steepening lapse rates and
an increase in instability and moisture, with most high-res models
hinting at increasing shower coverage along our eastern Straits
of Florida. Isolated showers (10%) are in the forecast for tonight
and Saturday as a result. 


An upper level cyclone will shift from the Central Plains to the 
Southeastern US Sunday through Tuesday. An orphaned frontal
boundary will linger across the Florida Peninsula, and
southeasterly flow will inspire a bit of isentropic upglide from
Cuba late this weekend. As the low approaches Sunday night, a 
weak warm front will bring local bulk shear (sfc-6km) in the 35 
knot range, with instability near 3000 j/kg along our warm coastal
waters. As a result, we have nudge rain chances upward a bit, and
introduced a isolated thunder into the digital forecast grids. 
The low begins to pull northward Tuesday night, its associated 
cool front slides through the island chain. The instability and 
shear are also present during this time period and MOS guidance 
reflects this trend, so isolated thunderstorms were also added to 
the Tuesday night period as well. Thereafter, dew points 
(previously in the low 70s) will migrate back to the upper 60s 
through the remainder of next week... a welcomed gift in late 


No watches, warnings, or advisories are in effect for the coastal
waters surrounding the Florida Keys. A trough of low pressure 
will move southward across the Florida Peninsula and eastern Gulf 
of Mexico, before dissipating near South Florida tonight. 
Thereafter, a high pressure area over the eastern United States 
will shift over the western North Atlantic Ocean. 


VFR conditions will continue at both terminals tonight with light 
winds from the northeast, shifting from the east Saturday morning.


On this date in Florida Keys weather history, in 1997, the low
temperature at Key West International Airport was 61 degrees. This
set the daily record for minimum temperature measured in Key West
on April 20th, a record which still stands 21 years later.
Temperature records at Key West date back to 1872.


Key West  73  85  78  84 / 10 10 30 20 
Marathon  73  86  78  85 / 10 10 30 20 




Data Collection......DR

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