099
FXUS62 KKEY 010116
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
916 PM EDT Sat Oct 31 2026

...New UPDATE, AVIATION...

.KEY MESSAGES...

- Coastal flooding will continue to gradually decrease over the
  weekend, but receding rates will be slow, especially in the
  Upper Keys.

- Gentle to moderate northeasterly breezes may freshen to moderate
  to fresh tonight, but are expected to slacken again tomorrow.

- A wet, stormy period is expected tonight through Monday. Locally
  heavy rainfall, if timed with high tides, may exacerbate coastal
  flooding hazards.

&&

.UPDATE...
Issued at 840 PM EDT Sat Oct 31 2026

It has been a difficult evening for trick-or-treat festivities
mainly for Key West as a continuous stream of shower and
thunderstorm activity has drifted northwestward near and mainly
just offshore of the island. While the majority of this activity
was just offshore, the lightning activity was very intense at
times with many strikes detected within 5 miles of the island
during prime trick-or-treating hours, many of which were positive
strikes. In addition, these storms were also very efficient
rainfall producers with MRMS 3-hr QPE data showing a swath of 3-5"
and locally 6" just offshore to the SW of Key West, narrowly
avoiding significant flooding impacts on the island. However, even
with the majority of the rainfall occurring offshore, an inch to
an inch and a half of rainfall occurred from Key West to Boca
Chica, which exacerbated the ongoing coastal flooding impacts that
have been observed recently. Fortunately, recent KBYX radar
imagery finally shows decreasing shower coverage at this time as
much of the area is worked over, especially across the Lower Keys.
While some additional activity will continue overnight, overall
coverage should remain isolated to scattered before increasing in
coverage further into Sunday as a shortwave trough brings
decreasing heights aloft. Overnight lows will fall to the mid 70s
with mostly cloudy to overcast conditions and no changes planned
to the ongoing forecast at this time.

&&

.DISCUSSION...
Issued at 320 PM EDT Sat Oct 31 2026

A broad high pressure system set up over New England and
Pennsylvania. Breezes along the Florida Peninsula freshened last
night as the pressure gradient tightened, and the high developed
enough to finally push breezes across the Keys back to east-
southeasterly. Keys residents could feel the increase in humidity
by stepping outside. Dew points across the Keys rose into the
upper 70s. Satellite derived Advected Layer PWAT late this
afternoon showed an increasing amount of moisture in the 700 to
500 mb layer. This lined up temporally with the development of
thunderstorms over the Florida Straits. The environment was in the
process of destabilizing and more than sufficient moisture is
present. All the environment lacks is a source of lift to organize
showers.

An upper level trough, the remnants of Tropical Storm Vance,
moved over the northwestern Gulf last night. This shortwave will
be able to travel along the Gulf Coast and provide a source of
upper level divergence starting early tomorrow morning. The
challenge with this trough is that the forcing will not be
focused. Ongoing wind convergence south of the Keys is broad.
Statistical guidance suggests PoPs may be able to approach 80
percent for portions of the Keys. However, the developing pattern
is not one that will last for a long period of time. The region of
enhanced divergence will move west of the Keys as early as Monday
night. While November may start out with a burst of rainy season
weather, we are steadily approaching the dry season.

Once the wet period comes to an end, the forecast for next week
becomes more uncertain. While broad layer ridging is expected to
prevail across the eastern United States, a strong mid latitude
trough is on track to develop over the Great Plains. Exactly how
much this trough is able to weaken the ridge is uncertain, and
model ensembles are not favoring one solution over another. In
essence, the ensembles are moderating the more extreme solutions.
Statistical guidance suggests a weak cold front may move across
the Keys late next week, but there is no agreement on the timing
or magnitude. Check back later, because we will have a better idea
of this frontal system after this weekend`s bout of moisture.

&&

.MARINE...
Issued at 320 PM EDT Sat Oct 31 2026

Small Craft Should Exercise Caution for increasing winds
headlines are in effect for the waters of Florida Bay, Bayside and
Gulfside waters, Eastern Hawk Channel, and the eastern Straits of
Florida. No additional watches, warnings, or advisories are in
effect for the waters surrounding the Florida Keys.

From synopsis: a broad area of high pressure over the eastern
United States will sustain gentle to moderate, occasionally fresh,
breezes across the FLorida Keys waters this weekend. Small Craft
Should Exercise Caution for increasing winds headlines are in
effect for portions of the marine zones tonight. Breezes are on
track to slacken tomorrow, but stronger winds along the east coast
will generate a higher northerly swell for the waters south of
the Upper Keys. Expect breezes to slacken during the weekend with
light to gentle breezes possible midweek. Shower chances will be
elevated through Monday with the peak expected on Sunday. Drier
conditions will be able to set up during the middle of the week.

&&

.AVIATION...
(00Z TAFS)
Issued at 840 PM EDT Sat Oct 31 2026

Mainly VFR conditions will prevail through the late evening hours
but rain chances will increase Sunday morning into the afternoon
hours. As a result, brief MVFR/IFR restrictions will be possible
at times if any of this activity brings direct impacts to either
of the island chain terminals. Surface winds will be out of the NE
at around 5-10 kts, though occasional higher gusts could occur,
especially in the vicinity of thunderstorm activity.

&&

.CLIMATE...
On this day in Keys Weather History, in 1999, the daily record
rainfall of 4.05" was recorded in Marathon. Precipitation records
for Marathon date back to 1950.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Warning until 5 AM EDT Sunday for FLZ076.

     Coastal Flood Advisory until 5 AM EDT Sunday for FLZ077-078.

GM...None.
&&

$$

Public/Marine/Fire...RG
Aviation/Nowcasts....RG
Data Acquisition.....AP

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