Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
FXUS62 KKEY 240854

Area Forecast Discussion
National Weather Service Key West FL
454 AM EDT Thu Aug 24 2017

An upper-level composite analysis this morning reveals a weak,
broad, and deep cyclonic vortex centered over the southeastern
Gulf of Mexico. This system is associated with a deep layer of
rich moisture and weak to moderate conditional instability.
Numerous showers and thunderstorms have been developing
periodically during the last 24 hours over South Florida and the
adjacent coastal waters. At the moment, the highest concentration
of showers per Doppler radar scans is along and north of a line
from Andros Island to Dry Tortugas National Park, with isolated
coverage over most of the Straits of Florida. A deep (but weak)
southerly flow has developed over the keys per Doppler VAD wind
profile measurements, with the center of the cyclonic vorticity
maximum located over the southeastern Gulf of Mexico. Mean sea
level pressure values at Key West and Marathon are seasonably low,
near 1010 mb, about 2.5 mb lower than yesterday at this time.
Multilayered cloudiness covers the region.

We adjusted 12-hour measurable rain chances upward for the next
few periods. The trough/weak vortex will meander around the
southeastern Gulf of Mexico and Florida Peninsula during the next
day or two, before it begins moving very slowly northeastward this
weekend. The moist, unstable, confluent flow will support ready
development of showers and thunderstorms. The combination of rich
moisture through a deep layer and a sheared upper troposphere will
create long-lived, precipitating nimbostratus and altostratus
decks, in addition to the active cumulonimbi. Locally heavy
rainfall will be possible for the next few days. A low-level ridge
may finally build in slowly from east to west, and north to south,
next week, with rain chances dropping gradually.

No watches, warnings, or headlines. Mostly variable breezes are
expected today and tonight. A weak trough will linger near South
Florida from today through Sunday. Winds and seas will be higher
in and near scattered to numerous showers and thunderstorms.

Prevailing VFR conditions are expected at both EYW and MTH today.
However, numerous showers and thunderstorms will develop around
the Florida Keys today, with short-lived, sub-VFR impacts likely
at both EYW and MTH.

On August 24, 1992 (25 years ago), category five Hurricane Andrew
made landfall in southern Miami-Dade County. Catastrophic damage
occurred in Homestead, with major damage in the Miami metro area.
The southern eyewall affected Ocean Reef in the upper Florida
Keys, causing damage to numerous buildings. Hurricane Andrew is
only the third category five hurricane to have made landfall in
the United States. The other two are Hurricane Camille (1969) in
Mississippi, and the Florida Keys Labor Day Hurricane (1935).

Key West  87  80  88  80 / 70 60 60 50
Marathon  91  80  91  79 / 70 60 60 50




Visit us on the web at

Follow us on Facebook and Twitter at: is the U.S. government's official web portal to all federal, state and local government web resources and services.