Area Forecast Discussion
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FXUS62 KKEY 071904

Area Forecast Discussion
National Weather Service Key West FL
304 PM EDT Tue Apr 7 2020

.SHORT TERM...(Tonight through Friday)
Quiet, dry weather will continue through Friday night. A surface
ridge axis will develop from east of the Bahamas westward through
the Straits and along the north coast of Cuba. The close proximity
will lead to a continuation of merely light and gentle breezes,
favoring a westerly direction starting Wednesday. The surface
ridge to our south will dissipate around Friday. Meanwhile, a
flat upper ridge over the Central Gulf will maintain warm and dry
conditions aloft, inhibiting convective development. Temperatures
will run about 2-5 degrees above normal for the rest of this week.


.LONG TERM...(Friday night through next Tuesday)
The extended forecast will feature the return of a few periods
with 10-15 PoPs, or a slight chance of showers and thunderstorms,
with more summer-like muggy dewpoints in the mid 70s creeping in
at times.

A mid-latitude surface high will uneventfully zip by to our north
and northeast on Friday night and Saturday. As it bridges across
South Florida and the Keys, it will bring a quick turn back to
more common easterly breezes on Saturday. Meanwhile, the upper
ridge over the Central and Eastern Gulf will flatten some on
Saturday, possibly weakening the thermodynamic cap enough for
convection to form over the Everglades. Westerly steering flow
aloft could then push mainland-borne convection out across
Biscayne Bay or the far Upper Keys. Therefore, Saturday PM is the
first small mention of SHRA/TSRA for the Upper Keys.

The upper ridge will rebound a bit over the Eastern Gulf on
Sunday, resuming the dry and hot forecast for Sunday and Sunday
night. However, low pressure should rapidly deepen over the Lower
Mississippi Valley on Sunday and move northeast, kicking up fresh
or possibly strong southerly breezes over the Keys.

The ridge will again flatten around Monday night or Tuesday. This
could allow a front to slip into North or possibly Central
Florida. The flattening ridge should also reduce the cap strength
a little. Of course, climatological 12-hour PoPs in April are
already near 10 percent, so will use the flattening ridge on Day 7
as justification for raising the forecast back to a near-climo
PoP forecast. If any convection does fire off, it will have
moderate instability to tap, so will include a mention of thunder
with the low-PoP forecast.


Weak gradients will prevail through Thursday night while a
diffuse Atlantic high pressure ridge noses in through the Straits
and along the north coast of Cuba. The ridge to our south will
dissipate Friday. High pressure will zip across the Southeast
States Friday night, heading east into the Atlantic on Saturday on
its way to Bermuda. This will bring a quick turn to easterly
breezes by early Saturday.

Strong low pressure will develop over the Lower Mississippi
Valley on Sunday, bringing freshening southeast and southerly
breezes. This is the first shot at getting a cautionary headline
of any kind in the marine forecast. The official forecast carries
15-20 knot southerlies on Sunday, but some statistical guidance
suggests 20-25 knot winds. Will let later forecasts move in that
direction if guidance holds with this solution.


Little change in the FEW-SCT coverage of fair weather cumulus over
the next 24 hours. Light and variable winds today will become
light west or northwesterly on Wednesday as a weak high pressure
ridge noses in through the Straits. A subsidence inversion will
remain around 2,500 to 3,000 feet MSL, with clear skies above.


Key West  76  84  76  84 / -  0 -  0
Marathon  76  86  76  86 / -  -  -  0




Data Collection......SDR

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