Windley Key, Florida Weather Forecast Discussion

330
FXUS62 KKEY 261752
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
152 PM EDT Fri Sep 26 2025
...New AVIATION...
.AVIATION...
(18Z TAFS)
Issued at 153 PM EDT Fri Sep 26 2025
VFR conditions will prevail at both EYW and MTH through the TAF
period. Dry air will limit shower activity therefore no mention of
VCSH at either terminal. Winds will be light and variable but
mostly east to southeasterly.
&&
.PREVIOUS DISCUSSION...
Issued at 1040 AM EDT Fri Sep 26 2025
A pleasant morning has been ongoing in the Florida Keys. KBYX was
previously detecting weak isolated showers across the coastal
waters, but a majority of that activity has diminished. This
morning`s 12z KKEY sounding revealed we are in a drier atmosphere
and MIMIC Precipitable Water agrees that we are in a "dry" slot,
though 1.7 inches of PWAT isn`t by any means dry. Temperatures
across the island chain are currently in the mid 80s, and coupled
with the light winds and limited cloud coverage, those will
continue to warm into the day. For the remainder of the day,
things will remain mostly quiet, though a cloud line could develop
over the Lower Keys producing a waterspout or two and isolated
showers. Winds will remain light and variable through the
afternoon. Due to the possibility of cloud line development this
afternoon 20% PoPs seems appropriate and therefore no updates were
needed to this package update.
&&
.FORECAST...
Issued at 414 AM EDT Fri Sep 26 2025
Conditions across the Florida Keys are still warm and muggy this
Friday morning. GOES East infrared satellite observations detected
lingering high altitude cirrus clouds and some low altitude
cumulus. KBYX and KAMX radar scans highlighted a line of showers
stretching from east of Fort Lauderdale to Floyd`s Wall in the
Florida Straits. Winds across the reef and the island chain
continue to be variable near about 5 knots. It is not a surprise
it feels extremely muggy, the lack of a breeze means moisture
remains trapped near the surface, and the evening 00Z sounding
sampled an environmental precipitable water value above the daily
75th percentile. Preparations for the day will remain the same as
earlier in the week, make sure to stay hydrated, stay in the shade
when possible, and wear sunscreen.
Currently, the weather pattern across the Keys is not too
complicated. The pressure gradient has been pretty weak across the
Gulf for most of the week. Weather phenomena have been driven by
a mixture of sea breezes, cloud lines, weak convergence
boundaries, and outflow boundaries. That comparative lack of
complexity is about to come to a very abrupt end. Tropical Storm
Humberto, which will not pose a threat to the Florida Keys, is
developing and expanding. A tropical wave over Hispaniola,
designated Invest AL94, is progged to continue northwest towards
the Bahamas. North and west of the Keys, a cold front is taking
shape over the central Gulf, which is attached to an upper level
trough digging south into the lower CONUS.
We are staring at the developing interaction between two tropical
lows in the western Atlantic and an eastward moving mid latitude trough
over the eastern CONUS. The environment east of the Keys is about
to become so chaotic it explains why numerical weather models
crunch more numbers than simulations of merging black holes.
Forecast specifics will become more clear with time, and high
confidence exists for a few topics. Breezes are forecast to back
northeasterly tonight and become northwesterly by Sunday night.
Wind speeds from gentle to fresh breezes are possible, though
moderate breezes over water are more likely. Shower coverage is
difficult, because as AL94 develops it will pull environmental
moisture towards its center. The mid latitude trough will also
direct drier continental air into the Gulf towards the Florida
Keys and inhibit shower formation late this weekend to the start
of next week. Statistical model guidance suggests shower chances
as low as 10 to 20% are possible this weekend. The forecast
package was put together while trying to find a middle ground
in the guidance. Showers are most likely Saturday night to Sunday
when the tropical wave is closest to the Florida Peninsula, but
before continental air reaches the Keys. Breezes may peak as early
as Sunday night, but probabilistic guidance suggests Monday to
Monday night as the most likely timeframe. Either way, please
check later updates for more information.
Conditions for the extended forecast are not at all certain. While
we can state winds will be westerly with high confidence, the
magnitude depends on what happens with AL94. Shower coverage is
also highly variable and depends on how long continental air is
funneled towards the Keys. It should be a bit cooler, and any
reprieve to dew points would be appreciated. Regardless of what
happens, the weekend is going to be busy.
&&
.MARINE...
Issued at 1040 AM EDT Fri Sep 26 2025
No watches, warnings, or advisories are currently in effect for
the Florida Keys waters. From synopsis, light and variable
breezes will persist through tonight while the pressure gradient
remains weak. On Saturday, a weak tropical wave, currently located
over Hispaniola, is forecast to move northwest towards the
Bahamas. Meanwhile, an upper level trough over the eastern CONUS
will move close enough to steer the developing low and support its
development east of the Florida Keys. Impacts for the Florida
Keys are expected to be moderate northwesterly breezes and
northeasterly swells along the Upper Keys.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...AP
Aviation/Nowcasts....AP
Data Acquisition.....DP
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NWS KEY Office Area Forecast Discussion