Area Forecast Discussion
Issued by NWS Key West, FL

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FXUS62 KKEY 220949
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
549 AM EDT Fri Mar 22 2024

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

.DISCUSSION...
Issued at 550 AM EDT Fri Mar 22 2024

...MULTIPLE ROUNDS OF STRONG TO MARGINALLY SEVERE THUNDERSTORMS
EXPECTED TODAY THROUGH SATURDAY...

An active overnight across the Florida Keys as the first of
multiple rounds of showers and storms moved through. This first
round was rather tame with generic thunderstorms. Rainfall totals
thus far from this first round has reached over a half inch,
especially in the Lower Keys. Elsewhere, rainfall has been much
lighter. East to southeast winds continue this morning with
sustained winds of 15 to 20 mph with gusts of 25 to 30 mph.
Similarly, across the marine platforms we have seen generally
near 20 knots with occasional higher gusts.

.FORECAST...
An upper-level trough will move into the western Gulf of Mexico
today. Ahead of the trough, a moist airmass will advect northward
into the central and eastern Gulf Coast. At the surface a low
pressure system is beginning to take shape with a warm front
extending eastward into the southeast Gulf of Mexico. Ahead of
the low, convergence is forecast to become maximized near the
warm front. The moist airmass, along with moderate deep- layer
shear and strong low- level convergence, will likely contribute to
a marginal severe threat. Scattered thunderstorms, associated
with lift ahead of the approaching system and the stronger
instability, are forecast to move into the Florida Keys by early
this evening. Convective coverage will likely gradually increase
as an MCS moves across the southern Florida Peninsula. Forecast
soundings in the Florida Keys this evening have 0-6 km shear of 50
to 60 knots, and 0-3 storm-relative helicity increasing to
between 250 and 300 m2/s2. This could support a threat of
marginally severe gusts, hail and a tornado or two will be
possible. In addition to the severe threat, flooding rains remain
a possibility as well. Storm totals through Friday night could
reach upwards of 4" with locally higher amounts possible. An
additional 1 to 2 inches is possible mainly Saturday morning.
Therefore, a Flood Watch remains in effect for now.

Ongoing convection will persist into Saturday. This convection
should tend to hamper daytime heating and related destabilization
Saturday morning as a southern- stream upper trough moves
eastward. An effective front/convectively reinforced outflow
boundary will probably be located over the Keys/Florida Straits.
The potential for weak to moderate instability to develop north of
this boundary remains questionable. Still, some guidance suggests
this may occur, especially if an overnight/early Saturday morning
MCS remains farther north towards the east-central Gulf and
central FL Peninsula.

Enhanced mid level flow of 50-70 knots in conjunction with the
aforementioned upper trough and strong deep-level shear will
conditionally support robust/severe thunderstorms, should they
develop across the Keys. Isolated damaging winds appear to be the
greatest threat with any thunderstorm clusters that can persist.
But, sufficient low- level shear should also be present Saturday
morning to pose some risk for a tornado. This isolated severe
threat will shift quickly offshore by Saturday afternoon in tandem
with an eastward-moving cold front.

Though the severe weather threat will subside Saturday evening,
winds will remain elevated behind the cold front. It will take
until Sunday afternoon before winds relax. As the next high
pressure builds in we could see a quick uptick in winds with
possible breezy conditions along the island chain on Monday.
Otherwise, quiet weather expected with near seasonal temperatures.
Keeping an eye on a new potential weather maker at the end of next
week but let`s get through this weekend first!

&&

.MARINE...
Issued at 550 AM EDT Fri Mar 22 2024

Small Craft Advisories are in effect for all of the Florida Keys
coastal waters. Strong east to southeast breezes will continue
this morning across the coastal waters of the Florida Keys as low
pressure develops in the Gulf of Mexico. Strong breezes will clock
around to the southeast and south today and will be accompanied
by strong to potentially severe thunderstorms. These thundery
squalls may come in multiple episodes today through Saturday, and
will be capable of damaging wind gusts, locally heavy rainfall,
and perhaps a violent waterspout or two. The heavy weather will
depart Saturday night as fresh to strong breezes shift to the
northwest. Breezes will shift quickly to the northeast then east
Monday and Monday night. Breezes will relax to gentle to moderate
by Tuesday.

&&

.AVIATION...
(06Z TAFS)
Issued at 550 AM EDT Fri Mar 22 2024

An active weather pattern will persist over the Florida Keys for the
upcoming TAF period. Early morning showers gusted to 26 knots out of
the southeast with MVFR CIGs. While light, stratiform rain will
persist through sunrise, VFR conditions will prevail for the first
few hours of the TAF period. The difficulty relates to when the next
line of showers reaches EYW. The next line of thunderstorms is
tracked to reach EYW near 21Z and could last up to four hours.
Lightning onsite is likely, requiring potential Airport Weather
Warnings. MVFR to IFR conditions are likely during this period of
time with gusts up to 30 knots possible. Weather conditions will
fluctuate rapidly, and amendments will be issued as necessary.

&&

.CLIMATE...

In 1941, the daily record rainfall of 0.78" was recorded in Key
West. Precipitation records date back to 1871.

&&

.PRELIMINARY POINT TEMPS/POPS...
Key West  81  74  82  70 /  80  90  80  20
Marathon  83  75  83  71 /  70  90  80  20

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through Saturday afternoon for FLZ076>078.

GM...Small Craft Advisory for GMZ031>035-042>044-052>055-072>075.

&&

$$

Public/Marine/Fire...LIW
Aviation/Nowcasts....AJP
Data Acquisition.....AJP

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