Area Forecast Discussion
Issued by NWS
FXUS62 KKEY 270242
Area Forecast Discussion
National Weather Service Key West FL
1042 PM EDT Wed Oct 26 2016
Changes to Forecasts -- Few changes were made to existing forecasts.
Only slight adjustments were made to the digital database.
Current Situation and Analysis -- The local air mass has modified
further during the last 24 hours, as evidenced by an increase in the
dewpoint temperatures by another few degrees F. In addition, both
the coverage and intensity of rain showers has increased during the
last 24 hours, with a few tops reaching 25,000 feet over the service
area, and higher over the south-central Gulf of Mexico, a few
hundred miles to the west, where lightning strikes have been
detected. An examination of data from the Key West evening
radiosonde balloon confirms a slight warming and moistening of the
lower troposphere, and a significant erosion of the inversion layer
around 6000-7000 feet elevation. A deep layer of dry air was still
present through most of the layer from 6000-26000 feet. The erosion
of the inversion layer is key, facilitating the transition from a
mostly stable to (weakly) unstable atmosphere across the service
area. The large-scale pattern is still dominated by the deep
anticyclone centered over the southeastern United States. However,
lower-tropospheric flow has become slightly more confluent and
moisture-laden. Such a trend will persist tonight and Thursday.
Currently, air temperatures in most Keys island communities are in
the mid to upper 70s, with dewpoint temperatures now near 70F most
Prognostic Overview -- Shower coverage should increase overnight,
with even a lightning strike or two not out of the question by
daybreak with some of the deeper cells. Strong breezes will
persist with some localized peaks and lulls. Winds will be higher
and gustier in and near the fast-moving showers. A wind gust of
35 knots was measured by the automated station at Molasses Reef
Light during a shower around 2030 EDT.
A Small Craft Advisory remains in effect for all Florida Keys
coastal waters zones. Sustained northeast to east winds near 25
knots with occasional gusts near 30 knots are expected overnight.
Seas will build to 8 feet in portions of the extreme southeastern
Gulf of Mexico beyond five fathoms, while seas build to 9 to 11
feet in the Straits of Florida. Higher and steeper waves will
occur in the Gulf Stream, where wind-generated waves oppose the
Through 27/24Z, prevailing VFR conditions are expected at both EYW
and MTH. Isolated to scattered showers with moderate to heavy
precipitation will move from about 080/28 knots overnight, and a
passage near or over EYW or MTH is a possibility but not likely.
Showers with MVFR or IFR ceilings and visibilities will be
increasingly likely after 27/12Z, with the best chance for sub-VFR
conditions, including potential thunderstorms after 27/18Z.
GM...Small Craft Advisory in effect for GMZ031-GMZ032-GMZ033-GMZ034-
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