No Name Key, Florida Weather Forecast Discussion

253
FXUS62 KKEY 220830
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
430 AM EDT Mon Sep 22 2025
...New DISCUSSION, MARINE, AVIATION...
.DISCUSSION...
Issued at 430 AM EDT Mon Sep 22 2025
KBYX radar has remained active through the entire overnight period
thus far. Earlier in the night, showers and an isolated
thunderstorm moved westward across the westernmost portions of
the Florida Keys. This activity was mostly driven by residual
boundaries and northeast to east breezes converging with east to
southeast breezes. This activity has since been dissipating.
Attention has now been turning to the nearshore and offshore
waters to the south of the Middle Keys where more widespread
showers and thunderstorms have been developing. This activity has
mostly developed over the last hour (230-330am). One of the cells
became intense enough to warrant a Marine Weather Statement over
the Elbow Cay area. However, even this cell has since been
starting to weaken. Otherwise, up until now the Island Chain has
remained dry. Since it has remained dry, the Island Chain has
remained quite warm for late September. Temperatures along the
Island Chain are in the lower 80s with dew points in the upper 70s
making it still feel like we are in the droves of summer.
High pressure remains over the Eastern Seaboard extending
southward towards Florida. However, the gradient weakens
dramatically from off the Carolina Coast southward towards
Florida. There is also a subtle inverted trough moving slowly
northwestward towards the Keys early this morning. As a result,
marine platforms around the Keys are observing northeast to east
breezes of 5 to 10 knots.
.FORECAST...
A broad upper trough across the Gulf will slowly lift to the
northeast through tonight. In conjunction with this, a weak
inverted trough is slowly propagating westward towards the Florida
Keys early this morning. In the lower to mid levels, there is also
a fair amount of moisture streaming into the area. GOES East
Total Precipitable Water (TPW) products shows mainly 1.9 to 2.1
inch PWAT across the area. However, lurking not too far away is
even moister air with PWATs generally of 2.2 to 2.3 inches.
Therefore, we have a supportive upper level environment, plenty
of moisture, and instability (00z evening sounding measuring CAPE
values near 3000 J/kg), we expect more widespread showers and
thunderstorms today and tonight. Due to this, 60% remains in the
forecast for these two periods.
As the upper level trough lifts northeastward, some weak ridging
builds into the region. However, some moisture will remain keeping
rain chances elevated for one more day on Tuesday at 50%.
Slightly drier air moves into the area for mid week through the
weekend resulting in 30% PoPs through the period. This is right
around average rain chances for this time of year. Otherwise,
typical summer weather is expected from Wednesday onward with
highs near 90 and lows near 80 with some lower 80s in areas.
&&
.MARINE...
Issued at 430 AM EDT Mon Sep 22 2025
There are currently no watches, warnings, or advisories in effect
across the Florida Keys coastal waters. From synopsis, as a
moisture surge pushes across the Florida Keys, rain and thunder
chances will be elevated for today through Tuesday. High pressure
over the Eastern Seaboard will continue sliding eastward today,
with light to gentle (occasionally gentle to moderate) east
breezes shifting to the east to southeast. Mainly light breezes,
occasionally light to gentle will prevail for much of the week, as
weak high pressure remains across the Florida Peninsula.
&&
.AVIATION...
(06Z TAFS)
Issued at 430 AM EDT Mon Sep 22 2025
While VFR conditions are expected at both EYW and MTH today, rain
chances will increase throughout today and into tonight. VCSH is
primed to start in the next hour or so at both terminals with
passing showers possibly resulting in periods of MVFR CIG and VIS
conditions. Outside of convection, near surface winds will be out
of the northeast to east at near 5 knots before increasing and
veering to the east to southeast.
&&
.CLIMATE...
On this day in Keys Weather History in 1959, a record low of 66
was recorded in Marathon. This is also tied for the coldest
temperature recorded during the month of September. Temperature
data for Marathon dates back to 1950.
&&
.PRELIMINARY POINT TEMPS/POPS...
Key West  88  79  89  81 /  60  60  40  30
Marathon  89  80  89  81 /  60  60  50  30
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...MJV
Aviation/Nowcasts....JAM
Data Acquisition.....JAM
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NWS KEY Office Area Forecast Discussion