Upper Key Largo, Florida Weather Forecast Discussion

735
FXUS62 KKEY 031857
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
257 PM EDT Fri Oct 3 2025
...New AVIATION...
.AVIATION...
(18Z TAFS)
Issued at 255 PM EDT Fri Oct 3 2025
VFR conditions are expected at both EYW and MTH for the rest of
today and into tonight. A lull in convective activity is slated to
start a few hours from now, but until then showers and occasional
thunderstorms continue to pulse around the island chain near both
terminals. Short term amendments will continue to cover immediate
impacts including MVFR CIGs and MVFR to IFR VIS with some gusty
winds. Outside of convection, near surface winds will be generally
out of the northeast to east at near 10 knots with frequent gusts
to 15 to 20 knots.
&&
.PREVIOUS DISCUSSION...
Issued at 1150 AM EDT Fri Oct 3 2025
Today marks the start of a wet and messy pattern for weekend in
the Florida Keys. Before sunrise this morning, a broken line of
scattered showers with a couple embedded thunderstorms developed
south of the Upper and Middle Keys before moving west towards the
island chain. While this activity continued to wax and wane on its
approach, a few showers were able to cross the Keys with MRMS 6
hour estimates averaging around a few tenths of an inch where rain
fell. The local maximum is over Boca Chica at just over half an
inch. More showers continue to develop behind the initial line but
are struggling to organize into thunderstorms. Meanwhile,
easterly breezes have become fresh along our offshore observation
stations. That along with partly to mostly cloudy skies has kept
temperatures in the lower 80s with some values in the upper 70s
where rain is either falling or freshly fell.
High pressure reaching down along the Eastern Seaboard is our main
supplier of easterly breezes. This accelerated flow is promoting
plenty of convergence for further development of shallow showers
in our waters. But why are they just shallow and not a bunch of
towering thunderstorms? This morning`s KKEY 12z sounding seems to
hold the answer as it depicts a solid layer of dry air starting
just above 700 mb. While a few overachievers have made it high
enough to throw some thunderbolts, they deteriorated rather
quickly afterwards. Thus chance to likely PoPs continue to look
appropriate along with a slight chance of thunder in the short
term. Tonight, guidance aims to moisten up more of the atmosphere
as a wave traverses over the Bahamas into our waters. This influx
of cyclonic flow will keep PoPs elevated but also slacken and veer
breezes as it traverses over our area tomorrow. Still plenty of
uncertainty in the forecast as we deal with smaller scale
features, but things are mostly in line with what was originally
expected so far. Stay tuned...
&&
.FORECAST...
Issued at 415 AM EDT Fri Oct 3 2025
A very messy and active weather pattern is expected over the
coming days. The aforementioned stationary boundary will remain
generally in place across the Bahamas and south Florida. This will
continue to generate showers and thunderstorms that will get
steered southwest to west across the Keys later today. Meanwhile,
a weak surface low will begin taking shape later today or tonight
and continuing into Saturday. This surface low will lie just to
the east of the Southeastern Bahamas. Any additional development
is expected to be slow to occur as this feature moves
northwestward across the Florida Peninsula. Regardless, this will
bring above normal rain chances for the Keys through the weekend.
By late Saturday, this feature will move into the eastern Gulf
basin. At the same time, the stationary front will begin lifting
northward as a warm front and the winds will briefly becoming
southerly. As the low travels further northwest and moves inland
over Louisiana, high pressure will back into the southeast U.S.,
including the Sunshine State. This will bring winds quickly back
from the northeast to east and freshen. A period of breezy
condition is possible starting late Tuesday and continuing into
midweek.
Lastly, the front that started all this mess will actually get
shoved back south. Models differ on how far south this will get
pushed through. The GFS wants more of a clean passage with dry air
filtering in behind and bringing a brief reprieve from the active
weather. The ECMWF is more pessimistic with the front stalling
either overhead or near the Florida Keys. This in turn would keep
rain chances above normal.
&&
.MARINE...
Issued at 1150 AM EDT Fri Oct 3 2025
Small Craft Should Exercise Caution in all coastal waters of the
Florida Keys. From synopsis, high pressure is slowly moving
across the eastern U.S., which will maintain a northeast wind
across our waters. This high will build into the western North
Atlantic, leading to freshening northeast to east breezes into
Friday evening. Winds will then briefly clock around towards the
southeast for the upcoming weekend and return from the east early
next week. Another period of moderate to fresh breezes is possible
starting Monday night. Expect an active weather pattern with
winds and seas expected to be higher in and around thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
Key West  77  88  79  89 /  40  30  40  40
Marathon  77  86  79  87 /  40  30  50  50
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 5 AM EDT Saturday for FLZ076.
GM...None.
&&
$$
Public/Marine/Fire...JAM
Aviation/Nowcasts....JAM
Data Acquisition.....JAM
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NWS KEY Office Area Forecast Discussion