Matecumbe Key, Florida Weather Forecast Discussion

776
FXUS62 KKEY 201810
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
210 PM EDT Sat Sep 20 2025
...New AVIATION, PREV DISCUSSION, FORECAST MARINE,...
.AVIATION...
(18Z TAFS)
Issued at 135 PM EDT Sat Sep 20 2025
While VFR conditions will prevail at both island terminals, shower
and thunderstorm activity developing over South Florida will have
to be monitored. Have elected to leave VCSH mention out of the
TAFs at this time. Near-surface winds will remain out of the
northeast at 6 to 10 knots.
&&
.MARINE...
Issued at 451 AM EDT Sat Sep 20 2025
No watches, warnings, or advisories are currently in effect for
the Florida Keys waters. From synopsis, as drier air continues to
push across the Keys and high pressure builds across the Eastern
Seaboard, drier conditions, coupled with light to gentle northeast
to east breezes, are expected through the weekend. This week,
moisture will return, but winds will remain light to gentle.
&&
.PREV DISCUSSION...
Issued at 1040 AM EDT Sat Sep 20 2025
Surface analysis places a sprawling area of high pressure over
the Southeast, supporting light to gentle north to northeasterly
breezes and mostly sunny skies on this September morning across
the Florida Keys and the adjacent coastal waters. The 12z sounding
at KEY sampled a moist, yet stable layer from the surface to
around 850 mb, with an even more stable and dry layer throughout
the rest of the troposphere.
The inherited forecast calls for slight rain and thunder chances.
Although it is tempting to take PoPs out completely for today,
there remains a low possibility of any convection over South
Florida diving southwestward towards the Middle and Upper Keys
late this afternoon or this evening. In addition, the mean low-
level northeasterlies may support a broken cumulus cloud line to
form along portions of the Lower Keys. Given these possibilities,
will stick with the current forecast.
&&
.FORECAST...
Issued at 451 AM EDT Sat Sep 20 2025
Through the weekend, the Keys will remain under the influence of
a broad ridge aloft with weak synoptic forcing. Low-level
northeast to east flow will continue to advect warm, humid air
into the CWA though precipitable water values are expected to
remain somewhat suppressed through Sunday from a relatively drier
airmass overhead compared to the climatological norm. This should
limit shower activity, although isolated pulse-like showers and
thunderstorms can never be ruled out this time of year. With
minimal convective inhibition, any showers that do form could
briefly intensify before collapsing producing a few lightning
strikes and gusty winds.
By early next week, deeper tropical moisture will return back into
the Keys as the ridge axis shifts. Increasing moisture will
enhance instability and allow for more convection to develop. Have
nudged PoPs up to 40% though guidance is suggesting higher which
will be re-evaulated as confidence increases. Towards late week,
drier mid- level air may move in again reducing shower chances
once again. Outside of convection, breezes throughout the week
will remain light to gentle.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...BT
Aviation/Nowcasts....BT
Data Acquisition.....BT
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NWS KEY Office Area Forecast Discussion