Area Forecast Discussion
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000
FXUS62 KKEY 030312
AFDKEY

Area Forecast Discussion
National Weather Service Key West FL
1012 PM EST Fri Dec 2 2016

.DISCUSSION...In the middle and upper levels(700-200 mb), latest
available IR satelitte imagery overlaid with model streamline
analysis as of 900 pm depict a sharpening full latitudinal positively
tilted trough oriented from Eastern Montana down to Northwestern Old
Mexico. Well downstream and to the southeast of that feature, the
center of an expansive deep and warm anticyclone was positioned near
Jamaica. South Florida and the Florida Keys lie on the northwestern
periphery of the deepest ridging with water vapor imagery delineating
very dry air.

At the surface and in the lower to middle levels,(Surface to 700 mb),
latest available marine and land surface observation and analysis
overlaid with IR satelitte imager as of 900 pm detail a 1020 mb cool
surface ridge oriented from Southern Minnesota to Northern Georgia.
Well to the south of that, a nearly stationary frontal boundary is
analyzed in the Florida Straits just south of the Florida Reef. The
00z evening sounding at Key West illustrated a gentle northeast to
east flow from just off the surface up to 850 mb, becoming light and
variable up to about 500 mb thence westerly with an exceptionally
moist lower to mid troposphere from off the surface up to almost 650
mb, with total columnar PWAT at 1.93 inches.

.CURRENTLY...Skies as of 900 pm across the islands are mostly cloudy
across the islands and adjoining waters. 11-3.9 micro differencing
product continues to indicate the likelihood presence of some stratus
across the immediate nearshore gulf waters north of the Middle Keys
and inside the 5 fathom line north of the Lower Keys as well as in
the Offshore Gulf waters 20 to 60 nm west of Mainland Monroe County.
Radar Correlation Coefficient Products detects chaff to the north of
the Keys, but there is a broken narrow band of showers from the Upper
Florida Keys southwest near the Florida Reef parallel to the Middle
Keys thence offshore well south of the Lower Keys.

.SHORT TERM...Overnight, latest available ECMWF and GFS model
forecast soundings illustrate drier air in the middle levels will
continue to work downwards through the column across the Keys. The
remnant line of showers will continue to move southwest, and a broken
line of showers will eventually affect a good portion of the Upper,
Middle, and Lower Keys. The band will then taper down toward
daybreak as the aforementioned dry air entrainment results in just
isolated showers. An earlier update was performed to put in scattered
showers over the islands, Florida Bay, Hawk Channel, and the
Nearshore Gulf waters north of the Middle Keys. Meanwhile, the 1030
mb surface ridge now over the Mid- Mississippi Valley will push
towards the Southern Smoky Mountains towards daybreak. This will
result in an overnight wind surge across all of the waters as breezes
pick up late tonight.

&&

.MARINE...Overnight, Small craft should exercise caution across the
Florida Bay and the immediate Nearshore Gulf waters north of the
Middle Keys for increasing winds overnight, except a small craft
advisory for increasing winds will be likely across the nearshore
waters inside the 5 fathom line north of the Lower Keys out to
Halfmoon Shoal Light, the Offshore Gulf Waters, waters around Rebecca
Shoal and the Dry Tortugas, Hawk Channel, and all of the Florida
Straits.

&&

.AVIATION...VFR currently exists at EYW & MTH, but a deck of MVFR
stratus exists across S Florida & a weak front that passed earlier
today is creeping back west toward the island chain. This
retrograding front may provide focus for another MVFR/IFR stratus
event and showers tonight and early Saturday morning. Confidence is
lower tonight than last night, in part due to higher observed winds.
Will evaluate more in the coming hours if the fcst needs to be
amended for more optimistic thresholds. Otherwise, expect
light/gentle NE winds to become moderate with gusts near 20 kts in
daylight hours.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...Small Craft Advisory Overnight GMZ033-034-035 &
042>044-052>055-072>075.

&&

$$

Public/Marine...Futterman
Aviation/Nowcasts....MCLOVIN
Data Collection/Upper Air......DR

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