Area Forecast Discussion
Issued by NWS Key West, FL

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000
FXUS62 KKEY 220232
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
1032 PM EDT Thu Mar 21 2024

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

.DISCUSSION...
Issued at 1032 PM EDT Thu Mar 21 2024

Tonight has been very calm in terms of convection, with KBYX
currently detecting no meteorological echoes within the Florida
Keys forecast area. Showers that developed along a convergence
line earlier this afternoon quickly waned, but not before dropping
almost a quarter of an inch in some island communities in the
Lower Keys. Winds, on the other hand, are the opposite of calm and
have increased further this evening, and are actually
overachieving in most locations. Sand Key C-MAN station has been
sustained between 20 to 25 knots most of the evening. Windy
conditions are ongoing along the island chain, and both the Key
West ASOS and the Marathon ASOS are recording sustained winds of
20 mph, with gusts around 30 mph. Water vapor imagery highlights
several clusters of convection rapidly moving east to southeast
across the Gulf of Mexico, with copious amounts of lightning being
detected within each cluster of storms. Some of this convective
activity is around 60 miles west of the Dry Tortugas and is ahead
of schedule. These storms are riding along a lower-level moisture
axis in an inhibited atmosphere. Looking at a synoptic scale,
CIMSS mean layer analysis features a trough moving across Texas,
which will be a big player in the Florida Keys sensible weather
over the next several days. This trough has suppressed ridging
even further, with subtle height falls sampled at almost all
significant levels by the 00Z sounding.

MOS guidance has winds increasing a few more knots, and as they
are already higher than expected, decided to nudge winds up a
little bit. Hi-res models are hinting at conditions deteriorating
by early tomorrow morning, but the storms on the periphery of our
western waters are closing in quickly. There is a potential for a
PoPs forecast bust tonight if this swath does manage to survive
until it reaches the island chain, and there is also a potential
for a bust if it does not. Have decided to nudge rain chances up
to 50%, as well as include thunder for all coastal waters, as well
as the island chain.

&&

.MARINE...
Issued at 1032 PM EDT Thu Mar 21 2024

A Small Craft Advisory is in effect for all Florida Keys coastal
waters. From synopsis, strong east to southeast breezes will
continue overnight across the coastal waters of the Florida Keys
as low pressure develops in the Gulf of Mexico. Strong southeasterly
breezes on Friday will be accompanied by strong to potentially
severe thunderstorms. These thundery squalls may come in multiple
episodes Friday through Saturday, and will be capable of damaging
wind gusts, locally heavy rainfall, and perhaps a violent
waterspout or two. The heavy weather will depart Saturday night as
fresh to strong breezes shift to the northwest. Breezes will
shift quickly to the northeast then east Monday and Monday night.

&&

.AVIATION...
(00Z TAFS)
Issued at 1032 PM EDT Thu Mar 21 2024

VFR conditions will prevail through the first half of the night,
then conditions will begin to deteriorate rapidly as the first
squall of a multi-day event rolls through. Have introduced VCSH
beginning at 08Z for EYW and 10Z for MTH. Decided to also go ahead
and include a TEMPO for the first squall tomorrow morning. There
is still uncertainty in exact timing and length of the event, so
amendments likely will be narrowed down as the timeframe becomes
more clear. Thereafter, have introduced VCTS to account for the
second round of storms. Decided not to include a TEMPO at this
time, as this round of storms may be after 00Z. Surface winds
outside of convection will be sustained at 15 to 20 knots, with
gusts of 20 to 25 knots. Wind direction will generally be east to
southeast aside from convection wind gusts, which will be from the
west to northwest.

&&

.CLIMATE...
On this day in 2003, the record high temperature of 85F and the
daily record low temperature of 79F were both recorded in
Marathon. Temperature records date back to 1950.

&&

.PRELIMINARY POINT TEMPS/POPS...
Key West  75  81  74  82 /  30  70  90  80
Marathon  75  83  75  83 /  30  60  90  90

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch from 5 AM EDT Friday through Saturday afternoon for
     FLZ076>078.

GM...Small Craft Advisory for GMZ031>035-042>044-052>055-072>075.

&&

$$

Public/Marine/Fire...NB
Aviation/Nowcasts....NB
Data Acquisition.....11

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