Upper Key Largo, Florida Weather Forecast Discussion

310
FXUS62 KKEY 100830
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
430 AM EDT Wed Sep 10 2025
...New DISCUSSION, MARINE, AVIATION...
.DISCUSSION...
Issued at 430 AM EDT Wed Sep 10 2025
Complicated mid latitude troughing remains dug in over the eastern
United States. Associated weak surface troughing persists across
Florida. With that said, the eastern flank of this trough is being
pulled northeastward by a shortwave trough lifting out over the
Atlantic states. This is leaving weak low pressure in the eastern
Gulf and contributing to a continued broadly confluent and very
moist environment in the Keys. After sporadic activity along the
Keys yesterday, boundary interactions helped to congeal a sizable
swath of activity rolling eastward through much of the island
chain last evening. This activity petered out a few hours ago, but
with scattered activity perking up over and beyond our deep Gulf
zones.
The previously mentioned Gulf surface low is expected to degrade
into a long trough straddling the Florida Peninsula today into
tonight. As a result, light to gentle southwesterly breezes are
expected to slacken further, becoming variable at times. Forecast
soundings suggest some drier air associated with a dying ridge to
our southeast will percolate into our area. This should allow for
somewhat lower rain chances over the next couple of days. Expect
near to slightly above normal temperatures with dew points
stagnant in the mid to upper 70s.
Confidence is slowly increasing that high pressure over the
eastern United States will expand southward late in the week,
moving into South Florida late in the week and possibly the Keys
this weekend. This will likely result in a modest strengthening of
broadly northeasterly breezes, with the stronger winds remaining
further north of our area. This will unfold as a mid latitude
trough amplifies, reaching deep into the Gulf. The amplifying
trough aloft should encourage the formation of surface through
lower level troughing off the southeast Coast. Should this occur,
it will assist in driving a long stalled boundary southward into
or past the Keys this weekend. Uncertainty remains high regarding
timing, position, and strength of any of these features. The
combination the lower level boundary, likely some upper level
support, and the associated increase in deep layered moisture
should bring about a period or two of considerably higher rain
chances. For now will maintain likely PoPs in the Friday night
through Saturday night time frame. Currently, not much in the way
of airmass change is expected with guidance suggesting dew points
may only briefly dip into the lower 70s, not very exciting.
&&
.MARINE...
Issued at 430 AM EDT Wed Sep 10 2025
A weak low in the eastern Gulf will wash out into an elongated
trough stretching across Florida today into tonight. As a result,
light to gentle southwesterly breezes will slacken with
increasing likelihood for variable periods. After a couple more
days of light and varying breezes, high pressure over the eastern
United States is expected to expand southward down the Florida
Peninsula, possibly reaching the Keys this weekend. This will
allow winds to firm up modestly out of the northeast. With that
said, uncertainty is high.
&&
.AVIATION...
(06Z TAFS)
Issued at 430 AM EDT Wed Sep 10 2025
VFR conditions are expected to largely prevail this morning at EYW
and MTH. Some passing shower activity producing sub-VFR conditions
is possible through the period based on guidance trends, primarily
after 12z, but uncertainty in coverage and timing precludes mention
in the TAFs for the moment. Thus, mention of more specific impacts
and categorical changes will be handled by future updates and
amendments. Winds will generally be from the south to southwest at 5
to 10 knots, becoming light and variable around 11/00z.
&&
.CLIMATE...
On this day in 2017, the eye of category 4 Hurricane Irma moved
across Cudjoe Key with maximum sustained winds 130 mph. Storm survey
evidence estimated the highest 3-second wind gusts on Big Pine Key
and Scout Key, at 150 to 160 mph. In the Florida Keys, 1,179 homes
were destroyed, 2,977 homes received major damage and 5,361 suffered
minor damage. More than 1,300 vessels were damaged or destroyed. The
storm surge reached 5-8 feet across the Lower Keys. WFO Key West
measured maximum sustained winds of 72 mph and gusts to 93 mph. Peak
measured gusts of 120 mph occurred at the Key Deer National Wildlife
Refuge and a private residence on Big Pine Key. Rainfall totals of 6
to 12 inches were measured at available rain gauges, with a maximum
of 12.54 inches at the Key Deer Wildlife Refuge on Big Pine Key.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...11
Aviation/Nowcasts....MC
Data Acquisition.....MC
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NWS KEY Office Area Forecast Discussion