Area Forecast Discussion
Issued by NWS Key West, FL

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682
FXUS62 KKEY 210902
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
502 AM EDT Fri Jun 21 2024

...New DISCUSSION, MARINE, AVIATION...

.DISCUSSION...
Issued at 500 AM EDT Fri Jun 21 2024
It is looking to a be a steamy start to Friday in the Keys this
morning. Temperatures across the island chain are currently in the
lower 80s with dewpoints in the mid to upper 70s. Offshore marine
observation stations are reporting moderate easterly breezes that
are notably lower in magnitude than the last few days. Convection
has been somewhat sporadic across the Straits of Florida
throughout the overnight hours, but a broken line of showers did
pass through the Lower and Middle Keys a few hours ago. Currently,
KBYX detects a few shallow cells popping up east of the Middle
Keys and trekking west towards land. Despite meager shower
coverage, most of the island chain is draped in a swath of high
clouds that spiraled off of the northeast edge of the Central
American Gyre (or CAG) planted on the Yucatan Peninsula.

A weak low with some associated convection has snuck over the
Bahamas to land just off the east coast of Florida. This places
said feature in between the high pressure centered just north of
Bermuda and the remnants of Tropical Depression Alberto over
southern Mexico. As a result, the tight pressure gradient that had
promoted fresh to strong breezes across south Florida earlier
this week has slackened. Today and through this weekend, breezes
will gradually lighten in response. This doesn`t mean we will lose
the influence of the CAG as the prevailing east to southeast
winds will draw a good deal of tropical moisture across the Keys.
In fact, CIMSS MIMIC TPW currently depicts the island chain on
the edge of a large moisture gradient with higher PW values
observed in the Straits of Florida.

With these features in place, today will be somewhat of a
transitional weather day across our CWA. Moderate easterly
breezes will start to bring in some of the previously mentioned
moisture while pushing some of the continental dry air currently
stuck over south Florida out of the way. While yesterday evening`s
sounding had a PW value measured over 1.6 inches, there`s still
some dry air mixed in that has kept most convection from reaching
thunderstorm status. Throwing in decreasing speed convergence due
to slackening winds and reduced surface heating due to high cloud
cover will result in less favorable rain chances than one might
infer from this set up. Opted to stay at a modest 40% PoP which is
above climatology for this time of year but also less than what
is to come.

Tonight and the rest of the weekend, as the low in the
western North Atlantic lands on the US coastline guidance
continues to pump spokes of moisture over the area with signs
pointing towards a period of wet, unsettled weather. Currently
holding at 50% PoPs through this weekend, but some MOS guidance is
in agreement for higher values Saturday. By the start of next
week, high pressure in the Atlantic will wrestle control back over
our winds and near normal PoPs are expected to return.

&&

.MARINE...
Issued at 500 AM EDT Fri Jun 21 2024
Small Craft Should Exercise Caution until winds decrease in the
Straits of Florida and Deep Gulf waters. From synopsis, a weak
low off the east coast of Florida has wedged itself between high
pressure centered north of Bermuda and the remnants of Tropical
Depression Alberto over southern Mexico allowing a slackening of
of east to southeasterly breezes over the next few days. Moisture
pulled into our area via the Central American Gyre will result in
waves of unsettled weather this weekend. High pressure building
over the North Atlantic early next week will result in light to
gentle southeast to south breezes.

&&

.AVIATION...
(06Z TAFS)
Issued at 500 AM EDT Fri Jun 21 2024
VFR conditions will prevail at the EYW and MTH terminals through
Friday evening. Above normal rain chances are expected, however
exact timing or coverage of convection will be difficult to
forecast, so have included just VCSH throughout the TAF period for
now. Short-term amendments will be issued as needed, based mainly on
radar trends. Short periods of MVFR or even IFR conditions will be
possible if convection directly impacts a terminal. Outside of any
stronger convection, surface winds will remain from the east at 7 to
12 knots.

&&

.CLIMATE...
On this day in Keys weather history in 1986, an F1 tornado caused
$250k in damage between Plantation and Tavernier. Tropical Storm
Bonnie formed in the central Gulf moving westward on the 23rd, so
this tornado may have been caused by the initial
depression/circulation.

&&

.PRELIMINARY POINT TEMPS/POPS...
Key West  88  79  88  79 /  40  50  50  50
Marathon  88  80  88  80 /  40  50  50  50

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&

$$

Public/Marine/Fire...JAM
Aviation/Nowcasts....Jacobson
Data Acquisition.....Jacobson

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