569 
FXUS62 KKEY 172006
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
306 PM EST Sat Dec 17 2022

...New DISCUSSION, MARINE, AVIATION...

.DISCUSSION...
Issued at 300 PM EST Sat Dec 17 2022 
GOES-16 satellite imagery is detecting mostly cloudy skies across
the island chain, with temperatures in the upper 70s. It remains 
quite muggy to the senses, with dew points in the lower 70s. The 
evolution of KBYX Doppler radar returns today has been quite 
similar to the evolution of yesterday, with the main convective 
activity limited to the Straits of Florida.

No major change to the overall thinking for the forecast for the
first few periods. The stalled frontal boundary over the Straits
of Florida will continue to work its way back northward this 
evening. This will result in continued veering (warm advection, 
large- scale forcing for ascent) throughout the evening and 
overnight hours. CAM guidance agrees with this evolution, with 
showers and thunderstorms likely proliferating in the western 
waters around midnight, before eventually pushing across the 
island chain overnight. Have elected to continue advertising 
likely PoPs (around 60%).

A second frontal boundary currently draped over the Florida 
Panhandle will finally push this primary frontal boundary south of
the Florida Keys tomorrow afternoon. This will promote a brief 
period of drying through Monday night, as high pressure builds 
across the Southeast. Deterministic and ensemble global guidance 
then pegs the next feature of interest as a shortwave trough 
promoting surface cyclogenesis over the Gulf coast. Indications 
are this trough will dive southeastward towards central Florida 
Tuesday through Tuesday night. Forecast soundings highlight a 
window of great veering, with storm-relative helicity values above
impressive 150 m2/s2 levels. Have decided to introduce thunder to
the forecast for these periods, and this will continue to be
monitored for potential stronger impacts.

There appears little in the way of cool advection in the wake of
this feature. Winds will quickly veer from the northeast, to
southeast, to southwest late in the week. This will be in the
response to what appears will be a powerful upper-level trough and
associated cold front pushing through the East Coast Friday and
Friday night. As is typical this time of year, there is quite a
bit of model spread and respective uncertainty with regards to how
strong the cold advection is behind this front. However, all
indications point towards below average temperatures for Christmas
Eve and Christmas Day for the Florida Keys. Current forecast 
calls for lows 55 to 60 Friday night, with highs in the upper 60s 
for Christmas Eve. It should be noted that this forecast is on 
the upper 50th percentile (warm) side of guidance, and should 
model trends continue, this may need to bumped further downwards.

&&

.MARINE...
Issued at 300 PM EST Sat Dec 17 2022
There are no watches, warnings, or advisories currently in effect
for the coastal waters of the Florida Keys. From synopsis, a
surface front stalled south of the island chain will lift back 
northward overnight tonight. Light to gentle southeasterly breezes
will veer to the southwest overnight. A reinforcing secondary 
front will push through the Florida Keys on Sunday. High pressure 
will build across the Southeast in the wake of the front, 
resulting in freshening north to northeast breezes Sunday 
afternoon through Monday. High pressure will weaken on Tuesday, as
a disturbance in the Gulf of Mexico pushes towards the Florida 
Peninsula. Winds will then quickly veer from the northeast, to the
southeast, and then eventually southwest ahead of a potentially 
much stronger cold front by the end of the week.

&&

.AVIATION...
(18Z TAFS)
Issued at 300 PM EST Sat Dec 17 2022
Showers will likely steer clear from both terminals until later 
this evening. Have introduced VCSH at 04z for EYW and 05z for MTH. 
Sub-VFR conditions are likely withing passing showers and 
thunderstorms. EYW could see some light rain over the next few hours 
as a cluster of decaying showers to the southwest of Key West moves 
to the northeast. There is a chance that after tomorrow's cold 
frontal passage for MVFR CIGS around mid-morning, however, 
confidence was too low to include at this time. Surface winds will 
rapidly shift clockwise ahead of an approaching front, with winds 
being southeast this afternoon at 6 to 10 knots, becoming southwest 
to west overnight. The veering will continue through tomorrow 
morning, and winds will be northwest to north at 4 to 7 knots. 

&&

.CLIMATE...
On this day in 2006, the daily record rainfall at both Key West 
(1.07") and Marathon (2.24") was recorded. Rainfall records in Key 
West date back to 1871, and 1950 in Marathon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Key West  79  72  79  69 /  40  60  30  20 
Marathon  80  72  79  69 /  40  60  30  20 

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&

$$

Public/Marine/Fire...BT
Aviation/Nowcasts....NB
Data Acquisition.....DR

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