Marathon, Florida Weather Forecast Discussion

481
FXUS62 KKEY 060221
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
1021 PM EDT Fri Sep 5 2025
...New DISCUSSION, MARINE, AVIATION...
.DISCUSSION...
Issued at 1020 PM EDT Fri Sep 5 2025
Compared to recent days, it has been a calmer late afternoon and
now evening across the Island Chain. KBYX radar showed an area of
steady rain with embedded thunderstorms earlier across the
easternmost portions of the area which dissipated a few hours ago.
An outflow boundary moved southward off the Florida Mainland into
Florida Bay and sparked some new showers between approximately 5
to 6 pm. These showers also quickly dissipated as fast as they
developed as they moved over the Bay. As the outflow boundary
activity was ongoing, there was also a fairly frisky thunderstorm
that moved eastward across the south-central Straits to the west
southwest of Elbow Cay. This cell prompted a Marine Weather
Statement earlier on. Additional storms formed ahead of it which
resulted in a cluster of showers and thunderstorms in the vicinity
of and including Elbow Cay. This activity was still ongoing as of
around 930-945pm. However, it has become more of an area of
steady rain now with any lightning and thunder having waned. GOES
East Nighttime Microphysics imagery shows mostly high level clouds
across the western areas of the Keys and then the cumulonimbus
clouds associated with the convection across the southeastern
Straits. Temperatures along the Island Chain are in the upper 70s
to lower 80s and dew points in the mid 70s. A weak area of low
pressure continues to meander over the east-central Gulf with weak
high pressure over to the east across the Bahamas. This is
leaving the Keys in weak flow. As a result, marine platforms
surrounding the Island Chain are observing south to southwest
breezes of 5 to 10 knots.
.SHORT TERM FORECAST...
The 00z evening sounding continues to show a very saturated
atmosphere through the most of the column. The only caveat is from
the surface to around 850 mb where a decent size dry layer is
present. Wind profile remains very chaotic from the surface to
around 3000 ft AGL. The PWAT value measured was 2.22 inches which
is slightly higher than the 90th percentile for the date. Overall,
no changes are expected to the ongoing forecast as the profile
remains quite saturated and it won`t take much to cause showers to
form.
&&
.MARINE...
Issued at 1020 PM EDT Fri Sep 5 2025
There are currently no watches, warnings, or advisories in effect
across the Florida Key coastal waters. From synopsis, a surface
trough will remain draped across South and Central Florida over
the next couple of days. This will keep winds gentle and very
broadly south to southwesterly. A moderate wind surge is possible
this evening on waters near Key Largo. The band of heightened
shower and thunderstorm potential will remain across our waters.
An Atlantic ridge will lift northward out of Cuba into the Keys
and South Florida this weekend. This will weaken and back winds
southerly. With that said, expect wind direction to be chaotic at
times. Shower and thunderstorm coverage will likely remain above
normal.
&&
.AVIATION...
(00Z TAFS)
Issued at 1020 PM EDT Fri Sep 5 2025
VFR conditions are expected to prevail through the TAF period.
Latest indications are for the terminals to remain dry through
much of the overnight hours. The uncertainty arises towards the
early morning through the afternoon hours Saturday. Given the
relatively still high rain chances for at least one more day and
at least some consistency on showers being near the terminals
during the aforementioned time, we went ahead and kept VCSH in the
TAF mainly after 06/12z. However, the timing and placement for
this activity remains uncertain and may be adjusted in subsequent
updates. Light and variable winds are expected to become south to
southwest overnight into Saturday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Key West  89  78  90  79 /  80  60  60  50
Marathon  87  78  89  80 /  90  60  50  50
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...MJV
Aviation/Nowcasts....MJV
Data Acquisition.....DR
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NWS KEY Office Area Forecast Discussion