Grassy Key, Florida Weather Forecast Discussion

438
FXUS62 KKEY 050230
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
1030 PM EDT Sat Oct 4 2025
...New DISCUSSION, MARINE, AVIATION...
.DISCUSSION...
Issued at 1030 PM EDT Sat Oct 4 2025
An inverted surface trough over the Bahamas is nestled within the
southern periphery of a sprawling high over the eastern United
States. As a result, winds are gentle and broadly out of the east
along the island chain this evening. Deep layered moisture climbed
quite a bit over the past 24 hours and this evenings sounding
indicated a precipitable water of 2.25 inches. This increase was
likely driven by an upper level trough across the Gulf and
associated reflection through the lower levels and surface. In
addition, CAPE was plenty sufficient to support deep convection.
All this along with confluent lower level flow contributed to
quite a bit of shower and thunderstorm activity across the area
this afternoon. More recently, most of this activity has shifted
west and northwestward out of the forecast area.
The Gulf trough is expected to shift northwestward towards the
Texas coast and help to pull the best lower level confluence
further away from the Keys. Meanwhile, the trough over the
Bahamas will ease a bit further northwestward towards the Keys and
South Florida. This will result in winds generally veering further
southeast and slackening. However, some variability is expected to
creep in. Deep layered moisture will remain elevated with ample
CAPE and weak inhibition. This along with the approaching inverted
trough and upstream radar trends justifies holding high chance
PoPs. This is slightly below statistical guidance. Overnight lows
will be in the upper 70s with dew points in the mid 70s.
&&
.MARINE...
Issued at 1030 PM EDT Sat Oct 4 2025
The combination of strong high pressure over the eastern United
States and adjacent Atlantic, and an inverted trough over the
Bahamas is resulting in gentle to moderate broadly easterly
breezes on Keys waters. The trough will shift a bit closer to the
Keys through the overnight and should result in winds relaxing and
veering southeasterly with some variability.
&&
.AVIATION...
(00Z TAFS)
Issued at 1030 PM EDT Sat Oct 4 2025
VFR conditions will prevail at the island terminals overnight.
With that said, scattered activity may result in periods of sub
VFR conditions. Surface winds will be gentle out of the east.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 5 AM EDT Sunday for FLZ076.
GM...None.
&&
$$
Public/Marine/Fire...11
Aviation/Nowcasts....11
Data Acquisition.....MC
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NWS KEY Office Area Forecast Discussion