Upper Sugarloaf Key, Florida Weather Forecast Discussion

502
FXUS62 KKEY 081738
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
138 PM EDT Mon Sep 8 2025
...New AVIATION...
.AVIATION...
(18Z TAFS)
Issued at 137 PM EDT Mon Sep 8 2025
VFR conditions will prevail at both EYW and MTH through the TAF
period. While showers are popping up in the coastal waters for the
time being not impacting either terminal therefore no mention of
VCSH. Near surface winds will be south to southwest at 5 to 10
knots.
&&
.PREVIOUS DISCUSSION...
Issued at 1120 AM EDT Mon Sep 8 2025
A mostly uneventful KBYX radar with only a few isolated showers in
our distant Straits. GOES-19 Satelitte reveals while the Lower and
Middle Keys are almost cloud free, the Upper Keys do have some
upper level clouds blocking some of the sun. Once again the 12Z
KKEY sounding measured ample moisture in the atmosphere with
MIMIC Precipitable Water confirming we are still in a moist
environment. Temperatures along the island chain are creeping from
the mid 80s into the upper 80s as the day heats up. Winds along
the Reef are mostly south and 5 to 10 knots. Today is expected to
be similar to yesterday with showers in a pulse-like nature
popping up in various areas across the coastal waters and island
chain but not amounting to much rain. For winds, they will remain
light and south to southwesterly. No changes were necessary to
this update forecast package.
&&
.FORECAST...
Issued at 415 AM EDT Mon Sep 8 2025
Mid latitude troughing over eastern North America and southern
stream troughing sweeping through the Gulf are contributing to
persistent lower level troughing over the eastern Gulf and across
Florida. In addition, this continues to maintain a broad swath of
very high precipitable water across Florida and the Keys.
Overall, a wetter than normal pattern remains across our area.
The troughing has also had a hand in crafting periods of broad low
level confluence across Florida and the Keys. After a mostly quiet
evening, shower and thunderstorms activity has increased quite a
bit across our area.
The lack of ridging at any level, along with the semi permanent
lower level trough across Florida and the Gulf, will maintain
higher chances for showers and thunderstorms for the next couple
of days. Adding to this, deep layered moisture will remain quite
high with forecast soundings generally depicting a nearly
saturated column through the troposphere. The overall weakness of
the lower level flow means mesoscale factors will often determine
timing and location of convective initiation. Will maintain high
chance to likely pops through this period. Expect seasonal
temperatures with dew points in the mid to upper 70s.
Rain chances may dip a bit heading into mid week. This is a result
of the trough to our north lifting a bit further north and as its
eastern flank is yanked away by a lifting out short wave trough
further north. Precipitable water is also expected to slip some
with modestly drier air showing up through the lower levels. With
that said, the environment will remain quite capable of showers
and thunderstorm development. A continued weak flow will keep the
door open for sea breeze and island cloud line triggers.
Guidance is becoming increasingly insistent that a stalled
frontal boundary, associated with the old surface trough, will
push southwards towards our area through the back half of the
week. This will be driven by complicated amplification of an
upper level trough over the eastern United States and Gulf. Not
only is deep layered moisture expected to still remain high, the
potential for upper level support will likely be on the rise as
short waves round the bottom of the trough within a diffluent
flow. The surface flow will remain chaotic and changeable due the
surface pressure field remaining poorly defined and perturbed
daily by diurnal and convective influences. As a result of the
above, have nudged PoPs up a bit for the mid to long range. With
that said, uncertainty is rather high.
&&
.MARINE...
Issued at 1120 AM EDT Mon Sep 8 2025
A Coastal Flood Statement is in effect for the Upper Keys waters
as minor saltwater flooding of low elevation streets and lots is
likely. Beyond that, no watches, warnings, or advisories are in
effect for the Florida Keys. From synopsis, a surface trough will
remain centered over the eastern Gulf and Florida Peninsula over
the next couple of days. This trough will be slowly sheared out
mid to late week. However, the pressure field in and around the
Keys will generally remain poorly defined. Moisture will remain
above normal. This along with the weak steering currents will
result continued above normal convective potential.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...AP
Aviation/Nowcasts....AP
Data Acquisition.....AP
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NWS KEY Office Area Forecast Discussion