-- Discussion containing changed information from previous version are highlighted. --
418
FXUS62 KKEY 241036
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
636 AM EDT Tue Sep 24 2024

...New DISCUSSION, MARINE, AVIATION...

.DISCUSSION...
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Issued at 634 AM EDT Tue Sep 24 2024
KBYX radar shows mostly scattered showers moving to the west near
20 knots across the Florida Keys coastal waters with these showers
occasionally moving across the Island Chain. For the most part,
these showers have remained below thunderstorm, but, the first
thunderstorm of the morning is trying to get going across the
western Straits of Florida. It is a very muggy and tropical late
September morning across the Keys with temperatures in the mid 80s
with dew points in the mid to upper 70s. Weak high pressure
remains in place across the Eastern Seaboard along with developing
tropical low pressure across the northwestern Caribbean Sea which
is still Potential Tropical Cyclone Nine per the National
Hurricane Center. This is creating for a tightening pressure
gradient across the Keys resulting in marine platforms observing
east to southeast breezes near 15 knots with Sand Key just now
starting to observe 15 to 20 knots. Island Chain communities are
observing near 15 mph with occasional gusts to near 25 mph.

.FORECAST...
In the upper levels, ridging remains in place across the Keys for
today, however, between 850 to 700 mb, we will see increasing
moisture which is expected to lead to increasing cloud cover and
higher rain chances than previous days with 40% maintained for
today. Also, the aforementioned pressure gradient is expected to
only gradually strengthen, therefore, we expect breezes to remain
fairly consistent on where they currently are for a majority of
the day.

Moisture continues to increase across the Keys tonight as the
tropical system in the Caribbean continues moving northwestward
towards the Yucatan Channel while potentially strengthening.
Therefore, maintained the 70% chance PoPs for tonight. Also,
breezes will continue to increase due to the deepening tropical
low pressure system and the high to the north across the Eastern
Seaboard.

Wednesday through Thursday is when we expect the wettest and
windiest weather throughout the Keys as the tropical system makes
its closest approach to the Keys Wednesday night. While the
forecast track of the system is expected to remain well west of
the Keys, there will be an expansive wind field with it resulting
in far reaching impacts. Therefore, it is important not to focus
on the exact path of the system as the effects will be far-removed
from the center. For the latest info on Potential Tropical Cyclone
Nine, please visit the National Hurricane Centers website for the
latest track and advisory information. Also, the Weather
Prediction has the Keys in a marginal risk for excessive rainfall
from Wednesday through Friday. The Keys can expect thundery
squalls over this time frame with strong gusty winds embedded
within the squalls.

Thursday night through Friday, as the system continues moving
rapidly northward due to increased forward speed making landfall
as a hurricane in the Big Bend area of Florida, we expect the
"tail" of the system to remain over the Keys prolonging the wet
period for a little bit longer.

Friday night through the weekend and into early next week, upper
level ridging as well as drier air moves back into the Keys
returning us to the typical early autumn pattern as we approach
the start of October. Temperatures will remain on the warm side
though near 90 degrees by day and lower 80s overnight.
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&&

.MARINE...
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Issued at 634 AM EDT Tue Sep 24 2024
Tropical Storm Watches are in effect for the Florida Keys coastal
waters westernmost marine zones along with Small Craft Should
Exercise Caution for Increasing winds today. For the easternmost
marine zones, Small Craft Should Exercise Caution for Increasing
winds are headlined for today along with Small Craft Advisory
Conditions expected Wednesday headlined. From synopsis, moderate
to fresh east to southeasterly breezes will continue today. This
will be in response to a high pressure building along the Eastern
Seaboard, and a tropical low developing in the northwestern
Caribbean Sea. Heading through the middle and later part of the
week, the forecast will depend on the development and movement of
this low. At this time, we expect fresh to strong east to
southeast breezes to develop late Tuesday, with strong southeast
winds peaking Wednesday night into Thursday as the tropical system
moves northward across the eastern Gulf of Mexico. The strongest
winds and highest seas are expected over western sections of the
Keys waters. Mariners should continue to closely monitor the
latest forecast updates during the next few days.

.COASTAL FLOOD...
A Coastal Flood Statement remains in effect for all of the Keys
island chain, as above normal tides continue. Boaters can expect
less clearance under fixed bridges, especially during the hours
around high tide.

A Coastal Flood Watch is now in effect for all the Florida Keys
from Wednesday evening through Thursday afternoon. Please see the
watch for more details.
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&&

.AVIATION...
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(06Z TAFS)
Issued at 634 AM EDT Tue Sep 24 2024
VFR conditions will prevail through the early morning for the 06Z
TAF period for EYW and MTH, but shower coverage will gradually
increase as PTC Nine moves northward. Near surface winds are
expected to increase to sustained moderate breezes after sunset,
especially at EYW with southeasterly gusts near 25 knots. Onset of
Tropical Storm force winds is most likely late Wednesday
afternoon or evening for EYW. MVFR to IFR conditions are possible
within fast- moving showers.
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&&

.CLIMATE...
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On this day in 1894, the daily record cold high temperature of
78F was recorded Key West. This observation tied for the coldest
high temperature recorded in September. Temperature records for
Key West date back to 1872.
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&&

.PRELIMINARY POINT TEMPS/POPS...
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Key West  89  81  85  81 /  50  70  90  90
Marathon  89  81  87  81 /  40  70  90  90
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&&

.KEY WATCHES/WARNINGS/ADVISORIES...
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FL...Coastal Flood Watch from Wednesday evening through Thursday
     afternoon for FLZ076>078.

     Tropical Storm Watch for FLZ078.

GM...Tropical Storm Watch for GMZ033>035-044-054-055-074-075.
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&&

$$

Public/Marine/Fire...MJV
Aviation/Nowcasts....AJP
Data Acquisition.....AP

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