Area Forecast Discussion
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FXUS62 KKEY 210155

Area Forecast Discussion
National Weather Service Key West FL
855 PM EST Mon Nov 20 2017

.DISCUSSION...In the middle and upper levels(700-200 mb) latest
available IR imagery overlaid with available model streamline
analysis as of 800 pm depict the center of deep warm core middle
and upper level ridging west of Baja California resulting in a
middle and upper anTicyclone encompassing the entire Western
CONUS, while downstream of that, cyclonic flow dominates the
Eastern CONUS and the Gulf of Mexico, with a well defined
shortwave trough axis sweeping eastward from the Mid-Mississippi
Valley down to the SW Gulf of Mexico. Water Vapor imagery
delineates ample middle and upper level dry air within the
cyclonic flow over South Florida and the Keys.

At the surface and in the lower to middle levels(Surface-700 mb),
latest IR imagery overlaid with marine and land surface
observations and analysis as of 800 pm detail the center of 1025
mb plus ridging located just east of Cape Hatteras. There is a
weak frontal boundary analyzed just south of the Lower and Middle
Florida Keys westward into the SE Gulf of Mexico. As a result of
the proximity to the boundary, the 00Z evening sounding
at Key illustrated a moderate to fresh and somewhat northeast to
east flow from the surface to 700 mb, with a saturated layer from
850 to 725 mb and total columnar PWAT at 1.53 inches.

.CURRENTLY...Skies as of 800 pm are mostly cloudy over the
Florida Keys and immediate surrounding waters. Radar detects
widely scattered showers impacting the immediate waters
surrounding both Middle and Lower Florida Keys. Temperatures
outside of showers over the islands are generally in the middle
70s with dewpoints closer to 70. C-man stations along the Reef are
still northeast around 20 knots, but island sensors are still
breezy at 15 to 20 mph.

.SHORT TERM...Overnight, the surface boundary just to the south of
the Keys will remain in place, while surface center east of Cape
Hatteras moves slowly away from the coast. Local winds are
expected to decrease during the second half of the night allowing
for winds and seas to fall below advisory criteria across all
waters. Given some confluent flow, isolated to widely scattered
showers will still linger near the Middle and Lower Keys
thru the rest of the evening, with most activity just to the
south, but low to middle level dry air will move across the Keys
from the west in the 850-700 mb levels. Available forecast
soundings do indicate PWAT falling down below 1 inch by 12Z. Hence
will be making a minor update to take pops down to isolated, 20%
over the islands.


.MARINE...Winds and seas will begin to come down more quickly
overnight as the MSLP gradient collapses. Nevertheless, will
leave in a headline across most areas for SCEC until the winds
subside and guidance suggests that will occur markedly. No
headlines or advisories expected during Tuesday


.AVIATION...short lived MVFR possible around KEY until about 04 or
05z, then VFR conditions expected at both KEY and MTH Int`l
terminals. Surface winds will veer more to 080-090 degrees and
decrease to aoa 8-11 knots.





Upper Air/Data Collection......DR

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