Lower Matecumbe Key, Florida Weather Forecast Discussion

961
FXUS62 KKEY 270216
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
1016 PM EDT Fri Sep 26 2025
...New DISCUSSION, MARINE, AVIATION...
.DISCUSSION...
Issued at 1015 PM EDT Fri Sep 26 2025
850-500 mb heights are falling slightly from earlier this
afternoon, with slight rises at 250 mb as the Keys are positioned
between a deep upper trough east of the Mississippi River into the
northern Gulf, a western north Atlantic ridge displaced well east
of the southeast U.S., and a formative tropical disturbance near
the northern coast of eastern Cuba. This evening`s sounding noted
increasing northerly high altitude winds as a remnant, persistent
trough southeast of the approaching robust southern U.S. trough
squeezes into a shear zone. The high altitude portion of trough in
the westerlies seems to be slightly lifting northward whereas its
lower portions continue to progress eastward. The sounding showed
only modest moisture increase mainly within a few thousand feet
of the surface, although there remains ample buoyancy. 700 mb
temperatures have cooled slightly, but with 500 mb temperatures
remaining steady, mid-level instability hasn`t increased that
much.
Southerly-directed outflow from mainland showers and a few
thunderstorms have brought slowly-drifting boundaries bayside,
with transient showers pretty much maturing and disappating within
a few miles of their genesis, and these small showers will likely
continue to pop up in a few spots where east late this evening and
overnight. boundaries and the earlier island convergence can
intersect. The slight rain chances look good for the Keys, and
while GOES precipitable water estimates (estimating about
0.10-0.15 inches lower than our evening sounding calculation),
it`s possible these values are 902close to 2.0 inches in the far
southeast portions of our Straits waters. We are watching the
deeper convection just east of our waters closely, however the
very light steering flow is more likely to become light north to
northeast by Saturday morning as the developing circulation of
Potential Tropical Cyclone Nine becomes more apparent in the
Straits west of Andros Island.
&&
.MARINE...
Issued at 1015 PM EDT Fri Sep 26 2025
No watches, warnings, or advisories are currently in effect for
the Florida Keys waters. Winds over the reef were near calm, with
light northeast winds noted Gulfside north of the Lower Keys. The
nearshore waters were indeed quite smooth this evening, with even
the buoy at Satan Shoal off the reef southwest of Key West
reporting a significant wave height at only four tenths of a foot.
From synopsis, Light and variable breezes will persist through
tonight while the pressure gradient remains weak. Potential
Tropical Cyclone Nine is expected to move north- northwest across
the central and northwestern Bahamas this weekend. Impacts for the
Florida Keys are expected to be moderate northwesterly breezes
and northeasterly swells along the Upper Keys.
&&
.AVIATION...
(00Z TAFS)
Issued at 1015 PM EDT Fri Sep 26 2025
Brief MVFR ceilings were noted at KMTH earlier as cloud-marked
boundaries and transient rain showers moved into the vicinity.
Otherwise, those temporary impacts are the limit with prevailing
VFR conditions and light, variable winds overnight. Light
northeast winds will likely begin soon after sunrise Saturday,
then backing out of the northwest in the afternoon with sustained
speeds below 10 knots.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...JR
Aviation/Nowcasts....JR
Data Acquisition.....MC
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NWS KEY Office Area Forecast Discussion