Fiesta Key, Florida Weather Forecast Discussion

534
FXUS62 KKEY 171814
AFDKEY
Area Forecast Discussion
National Weather Service Key West FL
214 PM EDT Wed Sep 17 2025
...New AVIATION...
.AVIATION...
(18Z TAFS)
Issued at 215 PM EDT Wed Sep 17 2025
VFR conditions will again be prevailing for EYW and MTH for the
18Z TAF period. Despite the earlier heavy rainfall, the general
atmospheric conditions will be relatively persistent. While rounds
of showers and thunderstorms are expected tonight, there are no
indications about when and where SHRA will form. Thus, one line
TAFs are issued because changes will be due to rapidly forming
SHRA. Expect amendments as showers and thunderstorms form.
&&
.DISCUSSION...
Issued at 1014 AM EDT Wed Sep 17 2025
Widespread cloud cover, disorganized showers, and bursts of
rainfall will define the rest of the afternoon across the Florida
Keys. Both KBYX and KAMX radars are detecting active showers and
thunderstorms across the offshore waters. A glance at GOES-E day
cloud phase imagery indicates a mess of high altitude debris cloud
and mid altitude stratiform with a few overshooting thunderstorms
around the Keys. Zooming out a bit to look at water vapor
imagery, a combination of deep moisture from the Caribbean, a very
sharp mid latitude trough, and a weak surface boundary are
focusing moisture over southern Florida. However, thunderstorms
are not yet widespread. The morning KKEY sounding highlighted a
couple reasons for the drier weather. The 925-700 mb layer was
most akin to a post convective environment. Winds rapidly veered
from easterlies to southwesterlies at about 5 kft. The sampled
PWAT rose above 2.10", but still below the 90th percentile for the
day. That may be related to the post convective environment, and
does not represent how much moisture exists over the Keys. Either
way, the radar is busy and expected to remain so through tomorrow
night. Make sure to keep checking the skies, keep an umbrella
nearby, watch the radar, don`t drive in flooded areas, and stay
tuned for additional updates.
&&
.MARINE...
Issued at 411 AM EDT Wed Sep 17 2025
Freshening northeasterly breezes today may lead to some Small
Craft Should Exercise Caution headlines later tonight,
particularly across the Florida Straits, as our forecast area sits
in a tightened pressure gradient. From synopsis, an unsettled
weather pattern is in place across southern Florida, and the
recent increase in showers and thunderstorms will remain in place
for the next couple of days. Freshening northeasterly to easterly
breezes will peak later tonight, and Small Craft Should Exercise
Caution headlines may be needed, particularly across the Florida
Straits. Breezes will slacken by tomorrow, but showers and
occasional thunderstorms will linger across the area through the
end of the week.
&&
.FORECAST...
Issued at 443 AM EDT Tue Sep 16 2025
We have done a lot of talking (typing) about this weak boundary
in the general area, and it looks like it will nudge its way back
into southern Florida today and tonight. As that happens, enhanced
moisture will lead to an increase in shower activity. The wettest
timeframe looks like it will be between Wednesday afternoon
through Thursday evening as probabilistic guidance is showing
anywhere from a 70 to 90 percent chance of any accumulating
rainfall during that period. There is still a lot of uncertainty
regarding how long this boundary lingers, but most of the guidance
suggests that some relief may come closer to the start of the
weekend. Guidance won`t be able to paint a clearer picture until
our weather becomes more active, so we will continue to convey the
low confidence in the extended forecast period. Overall, we are
entering yet another wet and soggy stretch, but the Florida
sunshine has to return eventually.
&&
.CLIMATE...
On this day in 2023, the daily record high temperature of 97F was
recorded in Marathon. This is also tied for the warmest temperature
ever recorded in the month of September for the Marathon area.
Temperatures records for Marathon date back to 1950.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...AJP
Aviation/Nowcasts....AJP
Data Acquisition.....JAM
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NWS KEY Office Area Forecast Discussion