Grassy Key, Florida Weather Forecast Discussion

211
FXUS62 KKEY 150857
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
457 AM EDT Mon Sep 15 2025
...New DISCUSSION, MARINE, AVIATION...
.DISCUSSION...
Issued at 238 AM EDT Mon Sep 15 2025
The overnight hours have been mostly unremarkable outside of the
handful of showers and thunderstorms that our KBYX radar has been
busy detecting. The activity that occurred in the vicinity of the
Upper Keys and Florida Bay earlier this evening has already
fizzled out, but the seemingly neverending boundary draped across
the Florida Straits has continued to trigger spicy thunderstorms.
CIMSS Vorticity notes a sloppily stacked vorticity maximum through
our forecast area, as well as a coinciding area of elevated PWAT
values. This will help to nurture additional showers and
thunderstorms in the Straits, but some dry air intrusion noted on
last night`s 00Z KKEY sounding should help to keep most of it
from lingering too long.
GOES-19 Satellite analysis still shows an area of low pressure
just offshore of the Carolina coast with a deep trough draped over
the region. Even though we are still situated at the base of this
trough, the low will gradually push north to northeastward over
the next few days, and the front will be allowed to retrograde and
make a return to southern Florida. This front will interact with a
building high over the Atlantic, and the tightening gradient will
lead to elevated breezes as well as a push of moisture by the
midweek. Rain chances are currently slated to peak sometime either
Wednesday or Wednesday night, and the middle of the week is
looking like it will just be a messy, wet period for the Keys.
Guidance is starting to suggest that the next opportunity for
drier conditions will be either over the weekend, or at the start
of next week, although confidence in this extended forecast is low.
All of this is to say that we should all appreciate whatever
Florida sunshine we can get today, because soggy weather is
returning again.
&&
.MARINE...
Issued at 238 AM EDT Mon Sep 15 2025
A weak frontal boundary will remain in the vicinity of the Florida
Keys coastal waters over the next several days. Weak undulations
of this feature while it interacts with high pressure to its
immediate north will result in a low confidence forecast for winds
and rain chances. Gentle to moderate northeast to east breezes
are expected to build in by Tuesday afternoon or night, as the
axis of the high pressure finally is able to spread down closer to
the Keys marine zones. During the middle of the week, over the
Wednesday and Thursday timeframe, will see freshening breezes and
Small Craft Exercise Caution headlines may be needed.
&&
.AVIATION...
(06Z TAFS)
Issued at 238 AM EDT Mon Sep 15 2025
Although an isolated shower and thunderstorm cannot be ruled out,
VFR conditions will prevail across the terminals through 06z
Tuesday morning. Near-surface winds will generally be light and
variable, favoring the east to southeast.
&&
.CLIMATE...
In 1907, the daily record rainfall of 4.92" was recorded in Key
West. Precipitation records for Key West date back to 1871.
&&
.PRELIMINARY POINT TEMPS/POPS...
Key West  90  80  90  78 /  40  30  40  50
Marathon  89  80  89  78 /  30  30  40  50
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...DP
Aviation/Nowcasts....BT
Data Acquisition.....BT
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NWS KEY Office Area Forecast Discussion