Area Forecast Discussion
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FXUS62 KKEY 211912

Area Forecast Discussion
National Weather Service Key West FL
312 PM EDT Fri Jul 21 2017

Showers from South Florida have overspilled into our nearby
coastal gulf waters and Upper Keys this afternoon, with Ocean
Reef recording a quick 0.13 inches despite a solid Saharan Air
Layer positioned across the Florida Keys. These showers are
spreading southward, but weakening quickly. Otherwise, weak winds
and clear skies (minus upper-level cirrus) exist across the
western Florida Straits. Temperatures range from the upper 70s
(where precip occurred) to the mid 90s.

The upper level pattern will remain zonal this weekend across the
CONUS and Atlantic Basin, and the axis of the Bermuda High will
gradually drift from the Keys northward to the Florida Peninsula.
The result will be weak southeasterly flow, which will allow the
SAL (Saharan Air Layer) to continue creeping across the Florida
Keys from the southwest. With an outflow boundary from collapsing
storms moving into our coastal waters, the best chance of rain
will be in the immediate short term, especially across the
nearshore Gulf Waters and Upper and Middle Keys. Afterwards,
passing showers in combination with the SAL take-over will likely
keep activity subdued for a little while. Therefore, below average
POPS will continue overnight and into Saturday.

Low level moisture will begin to recover Saturday night as the
SAL becomes elongated and pushes into the central gulf. The jet
stream will also begin to shift eastward and push a weak trough
across the eastern CONUS early next week. At this point in time,
the normal climatological pattern will take over for our county
warning area. This translates back to 30 percent rain chances and
prevailing easterly flow, with nearby land giants occasionally
sending bundles of convection into our coastal waters.


Light to gentle breezes out of the south will continue as the
ridge axis shifts northward to the Florida Peninsula. Expect
gradually increasing flow through the weekend and early next week,
but pleasant boating conditions will likely prevail as the ridge
axis remains somewhat nearby into next week.


Generally VFR conditions expected through the period. A band of
scattered showers and isolated thunderstorms moving through the
middle and upper Keys will steadily weaken through 21Z. Have VCSH
in the KMTH TAF this period. Otherwise...only isolated showers are
expected with coverage too low to mention in the TAFs. South to
southeast winds 5 to 8 knots through the period. 34/MM




Data Collection......Vickery

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