084
FXUS62 KKEY 291937
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
337 PM EDT Tue Sep 29 2026

...New AVIATION...

.KEY MESSAGES...

- Moderate to major saltwater flooding of low elevation streets
  and lots is likely to continue over the next few day or so due
  to King Tide. Don`t drive through flooded roadways. Boaters can
  expect less clearance under fixed bridges.

- A Coastal Flood Warning is in effect for the Upper Keys,
  particularly along the sounds, bay side of Key Largo. A Coastal
  Flood Advisory is in effect for the Middle and Lower Keys.

- A wet pattern is expected for the next several days across the
  Keys. This will maintain above normal rain and thunder chances
  through at least Thursday.

&&

.AVIATION...
(18Z TAFS)
Issued at 256 PM EDT Tue Sep 29 2026

Widely scattered to numerous SHRA and occasional TSRA will move
across the region through this evening with occasional MVFR/IFR
restrictions, especially during pockets of heavier rainfall. There
may be a brief lull in the late evening and overnight hours before
additional activity develops again Wednesday morning through the
end of the period. Winds will remain out of the SE through tonight
but will shift to a more easterly direction on Wednesday at 10-15
kts and occasional gusts to 20 kts. While VFR conditions will
generally prevail outside of convection, elevated rain chances
will maintain potential of restrictions most times throughout the
period.

&&

.UPDATE...
Issued at 1129 AM EDT Tue Sep 29 2026

Deep tropical moisture continues to surge into the Florida Keys as
upper air analysis shows troughing with a slight positive tilt
extending into the Yucatan region and western Caribbean and a
mid/upper level anticyclone positioned in the subtropical Atlantic
southeast of Bermuda. Meanwhile, a 55-65 kt jet streak analyzed at
250 mb is streaming across the Florida peninsula, providing plenty
of divergence aloft across the region and this will generally
remain in place through the remainder of the day as the upper
trough axis remains to our west. Given the favorable forcing for
ascent and deep moisture with PWATs around 2 inches or more,
rounds of scattered to occasional numerous showers and embedded
thunderstorms will drift in a general northeastward direction
across the Island Chain and surrounding coastal waters the
remainder of the day. The 12Z KEY RAOB shows good moisture in the
mid and upper levels with some dry air and inhibition in the low
levels, likely related to the more stable and post-convective
environment that was in place earlier. Forecast soundings through
the remainder of the day do maintain somewhat drier air in the
lower levels, which may be indicating some Cuban shadow influence
from low level southerlies. However, the aforementioned dynamics
should be able to overcome these potential limiting factors
enough to still support likely PoPs so will continue with the
inherited forecast. With this overall environment of deep moisture
and ascent, coupled with the background of elevated tide levels,
the main concern will be locally heavy rainfall and flooding,
especially during high tide cycles and in areas that typically
experience King Tide flooding. Otherwise, dewpoints have returned
to the mid 70s area-wide and with highs reaching the mid/upper 80s
later today, the more typical warm and humid feel to the air in
late September is back after the recent multi-day slight taste of
fall.

&&

.DISCUSSION...
Issued at 436 AM EDT Tue Sep 29 2026

An incredibly messy but dynamic weather pattern is setting up
across the Florida Keys this morning. Let`s break it down. At the
surface we have weak ridging occurring which is leading to
chaotic, but light surface winds. In the lower levels the ridge
axis of an Atlantic Ridge lies just to our south but is steadily
marching northward. In the mid and upper levels we have a
pronunced, deep trough that extends from near the Great Lakes
Region well south across the Gulf Basin and into the western
Caribbean. This feature is providing broad cyclonic flow aloft as
well as the occasional shortwave that has ejected northeastward.

The aforementioned Atlantic Ridge axis will continue lifting
northward today. As it does, it will help to align our surface
winds more out of the east to southeast. In addition, the steering
flow more become more southerly, allowing for better moisture
transport from the western Caribbean ahead of the mid/upper level
trough. Thus far the trough has resided to our west with a
plethora of convection erupting throughout the last day or so.
However, as this activity tries to move northeast and away from
the trough, it has encountered more stable and relatively drier
air. This has kept much of the precipitation from reaching the
Florida Keys.

Today should be the transition point for the Keys. The mid/upper
level trough will slowly edge eastward today allowing for a better
alignment of moisture and lift. The fly in the ointment is the low
level ridge axis lifting northward. This will cause a southerly
wind below 700 mb and could bring in low level dry, warm air
advection. This may counter the increasing moisture aloft, leading
to an overall lower coverage of showers and thunderstorms for
today. Hi-res CAMs continue to advertise that we will have enough
synoptic forcing to overcome the more mesoscale effects. Time will
tell if this actually happens.

Once this feature sets in, we can expect multiple days of wet,
active weather through at least Thursday. Thereafter, a ridge out
across the Atlantic will shift further to the west and retrograde
the mid/upper level trough into the Bay of Campeche. This would
lower our rain chances back closer to normal with a moist east to
southeast flow.

&&

.MARINE...
Issued at 259 PM EDT Tue Sep 29 2026

A high pressure system across the eastern third of the U.S. will
steadily shift east into the western Atlantic through tonight. As
it does, east to southeast winds will remain in place. Thereafter,
this high will shift further offshore and merge with an existing
high pressure across the subtropical Atlantic and subsequently
build through the remainder of the week. This will promote
freshening breezes with an increasing likelihood of moderate to
fresh breezes beginning Wednesday, continuing through late week.
There is a good chance that marine Cautions may be required for
portions of Keys waters at that time, and Advisories cannot be
ruled out. In addition, a very wet pattern will remain across the
Keys over the next few days, resulting in periods of scattered to
numerous showers and thunderstorms.

&&

.AVIATION...
(18Z TAFS)
Issued at 256 PM EDT Tue Sep 29 2026

Widely scattered to numerous SHRA and occasional TSRA will move
across the region through this evening with occasional MVFR/IFR
restrictions, especially during pockets of heavier rainfall. There
may be a brief lull in the late evening and overnight hours before
additional activity develops again Wednesday morning through the
end of the period. Winds will remain out of the SE through tonight
but will shift to a more easterly direction on Wednesday at 10-15
kts and occasional gusts to 20 kts. While VFR conditions will
generally prevail outside of convection, elevated rain chances
will maintain potential of restrictions most times throughout the
period.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Warning until 7 AM EDT Wednesday for FLZ076.

     Coastal Flood Advisory until 7 AM EDT Wednesday for FLZ077-078.

GM...None.
&&

$$

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

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