Area Forecast Discussion
Issued by NWS Key West, FL

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FXUS62 KKEY 282100

Area Forecast Discussion
National Weather Service Key West FL
400 PM EST Sun Feb 28 2021

A Bermuda High remains anchored across the western Atlantic with
a ridge axis extending west southwest across Florida and the Gulf
of Mexico. This has maintained breezy conditions across the island
chain and surrounding waters. The Bermuda High in combination
with deep layer ridging occurring across the southeast U.S., is
keeping the region under mostly sunny skies with very low (< 10
percent) PoPs.

BYX radar shows some lingering isolated sprinkles moving along in
the southeast flow but nothing more impressive. The aforementioned
deep layer ridging is suppressing vertical growth, which is
evident based on visible satellite and this morning`s 12Z RAOB
sounding, which showed multiple inversions. There is enough low
level moisture trapped below these inversions that fair weather cu
have proliferated in the southeast flow. Otherwise temperatures
across the island chain are in the lower to 80s with dew points
in the lower 70s. Thankfully breezy conditions are keeping the
muggy conditions at bay.

The Bermuda High will weaken and retreat eastward in response to
an energetic upper level trough traversing across the Central and
High Plains. This trough is beginning to phase with the
subtropical jet riding over top of the ridge over the southeast
U.S. and is helping to amplify a surface low in the Upper Great
Lakes region. This low will eject east and will help to push the
Bermuda High sufficiently east that the ridge axis across our area
will begin to weaken. This will lead to decreasing winds for
Monday into Tuesday. The aforementioned low pressure will slide an
attendent front southward and will stall along the north Gulf
coast late Monday night.

Meanwhile, a potent shortwave will move east from the
Intermountain West and push into the Red River Valley by Tuesday
afternoon. As this occurs it will begin to interact with the
stationary front and a new surface low will begin to develop near
the mouth of the Mississippi River Tuesday evening. As a result
our winds will turn from the south and southwest going into
Wednesday. A weak cold front will then slide through late Wednesday
afternoon and evening with winds clocking around to the northwest
and north. This will begin the ushering in of a cooler air mass
with temperatures returning to near or slightly below normal.

Thereafter a continental high will move southeast, settling
across the southeast U.S., while gradually weakening. This will
keep our winds generally from the north, while at times wavering
between northwest and northeast. Then a stronger Canadian High
(1036 mb) will quickly surge southeast and build along the Eastern
Seaboard. As this occurs, the pressure gradient will tighten in
response. Just how much strengthening occurs remains in question
but winds generally will increase over the weekend in response.
Regardless of strength, this next high will bring a reinforcing

Rain chances through the first half of the period will remain low
(<10 percent). As the front approaches from the north and
northwest on Wednesday, we could enough moisture pool ahead of the
front with some confluence that isolated showers couldn`t be ruled
out. Otherwise chances increase slightly with the passage of the
front Wednesday evening into early Thursday. Rain chances return
again Saturday as the base of a trough moves across the Florida
Keys, where enough lift may overlap with moisture pooling along a
speed surge associated with the reinforcing front.


Winds are gradually slackening across the area. With that said
Small Craft Advisories (SCA) remain in effect for the Florida
Straits, with Small Craft Exercise Caution (SCEC) headlines
currently in effect for most waters with the exception of the Gulf
waters within 5 fathoms and the offshore Gulf waters. We will see
one last nocturnal surge this evening with SCA continuing for the
FLorida Straits. SCEC will be in effect for all waters with the
exception of the offshore Gulf waters beyond 5 fathoms. Bermuda
High will weaken and slide east in response to an approaching
front that will settle across the north Gulf coast. This will lead
to slackening winds Monday through Wednesday morning. By Wednesday
afternoon, the front along the Gulf coast will once again start
moving and slide across the region late Wednesday afternoon into
the evening. This will lead to winds clocking around to the
northwest and north. High pressure will slide south from Canada
and anchor along the north Gulf coast. This will lead to a period
of peaks and lulls Wednesday night through Thursday night. Winds
slacken once again Friday. A reinforcing front will approach the
area late Saturday with freshening breezes.


VFR conditions will prevail at the Key West and Marathon terminals
through 18Z/01. High pressure will control the weather across the
Florida Keys, allowing for only a very slight chance of rain. Winds
E-SE 10 to 15 knots with occasional gusts over 20 knots.


In 1982-1983, Key West experienced its wettest winter on record
with a total rainfall of 21.42". Precipitation records date back
to 1871. Meteorological winter is defined as Dec 1st - Feb 28th.


Key West  76  84  75  83 / -  0 -  0
Marathon  76  85  75  84 / -  0 -  -


GM...Small Craft Advisory GMZ052>055- 072>075.



Data Acquisition.....DR

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