Area Forecast Discussion
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FXUS62 KKEY 200045

Area Forecast Discussion
National Weather Service Key West FL
845 PM EDT Mon Mar 19 2018

.DISCUSSION...In the middle and upper levels(700-200 mb), latest
available GOES 16-R satelitte imagery overlaid with model
streamline analysis as of 800 pm depict mostly low amplitude
troughing/weakly zonal middle and upper flow across the entire
CONUS. the next shortwave trough axis in development was situated
from the Northwestern High Plains to the Central High Plains.
There was a developing mid-level cyclone (at 500 mb) near the
Mid-Mississippi Valley. But south of that, there exists a mainly
zonal fast moving upper flow, with just weak impulses and 75 to
100 knotters at 250 mb, presently traversing the breadth of the
Southern Gulf of Mexico, as well as the Florida Keys.

At the surface and in the lower to middle levels (Surface to 700
mb), latest land and marine surface observations and analysis as
of 800 pm, detail a 998 mb low pressure system over the Mid-
Tennessee Valley with attendant cold frontal systems spoking out
to the south and west. Given dynamics and moisture, ample severe
weather and tornado threats exist from this area westward to the
Mid-Mississippi Valley. The next cold front to move across the SE
Gulf, as well as Southern Florida and the Keys, is the one which
is draped from near Memphis to just offshore of S Texas near
Brownsville. The 00Z evening sounding at Key West illustrated a
fairly dry yet moistening lower to mid tropospheric profile and
PWAT only at 1.27 inches, with a light and variable flow near the
surface becoming gentle to moderate and southwest only at 950 mb
becoming strong west to northwesterlies above 700 mb.

.CURRENTLY...As of 800 pm, skies are mostly clear across the
entire service area, except for maybe some thin leftover mid-
level blow off or remnant convective clouds just moving off of
Cuba. Temperatures across the islands remain warm in the upper 70s
with dewpoints in the lower 70s. C-man stations along the Reef are
light and variable west of the 7 mile bridge, but gentle to
moderate southwest winds east of the 7 mile bridge.

.SHORT TERM...Overnight, the aforementioned middle level low
pressure system in tandem with the surface low will pull
northeastward overnight, with the surface low moving up into the
Upper Ohio Valley. The surface cold front now over the Western
Gulf will move towards the Central Gulf by morning. Light and
variable winds will become light to gentle or gentle south to
southwesterly by 12Z. Forecast soundings illustrate low level
veering but with insufficient moisture. The only chance for a
shower would be in the well offshore Florida Straits very late. No
changes will be made to the package on this cycle.


.MARINE...Gentle breezes, variable at times but generally out of the south
to southwest, are expected this afternoon. An Atlantic ridge of
high pressure will extend across Cuba tonight. A cold front will
progress southward down the Florida peninsula Tuesday. This cold
front will pass through the Florida Keys Tuesday night. An area of
high pressure over the Southeastern United States will build
southeastward down the Florida peninsula Wednesday through Friday.



Some brief MVFR ceilings might occur between 10Z to 18Z, and these
cloud bases should be between FL010 and FL015. Southwest winds will
gust to near 15 knots after 20Z, just ahead of a rain-starved
frontal system moving through the Keys shortly after 21/00Z.


In 2013, the daily record rainfall of 1.28 inches was recorded in
Key West. Rainfall records date back to 1871.




Data Collection......Chesser

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