Area Forecast Discussion
Issued by NWS Key West, FL

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FXUS62 KKEY 230242

Area Forecast Discussion
National Weather Service Key West FL
1042 PM EDT Thu Oct 22 2020

The setup this evening is similar to the last two evenings. The
air mass is extremely moist by late October standards, with an
observed PW value of 2.25" in the 00z KEY sounding. We are still
in the somewhat tight pressure gradient between broad low pressure
over the northwest Caribbean and a strong high pressure ridge
wedging down the U.S. Atlantic coast east of the Appalachians.
Fresh easterly breezes continue to provide small- scale forcing
thanks to focus in the form of localized speed surges and zones of
confluence lined up in the flow. The air mass is still moderately

So similar to last night, we started the evening quietly, but
shower activity has been picking up and will continue to become
more widespread through sunrise. Basically, a wet overnight is in

Little change is expected through Saturday, while a broad low
tries to form south of Cuba near the Isla de la Juventud (Isle of
Youth). This should bring a southeast turn of our low-level flow,
but that will actually increase low-level convergence as those
southeasterlies meet up with northeasterlies that will still
prevail over the FL Peninsula. So the uncommonly long stretch of
wet weather will continue over the FL Keys.

As we saw in Key West this morning, if a quick inch of rain occurs
during the morning high tide, it will be quick to cause flooding.


The Keys waters lie in a somewhat tight pressure gradient between
two features. The first is a weak area of low pressure between
Jamaica and the Yucatan Peninsula. The second feature is a ridge
of high pressure east of the Appalachians. The interaction between
these features will keep moderate to fresh easterly breezes over
the waters through Friday. Thereafter, high pressure to our north
will gradually weaken, as the trough to our south move northeast
through the Straits toward the Central Bahamas on Saturday and
Saturday night. Winds will abate appreciably on Sunday.


Scattered to numerous showers are expected at both terminals
overnight and into tomorrow. These showers will bring MVFR or IFR
conditions and gustier winds. A similar wet pattern to the one we
have seen the past few nights is expected again tonight, so put
prevailing SHRA from 8Z to 17Z with VCSH after 17Z. Expect
amendments and TEMPOs for any stronger activity that may pass over
the terminals. Outside of any shower activity, surface winds will
be out of the east near 10 knots with higher gusts.


FL...Coastal Flood Advisory for FLZ076.



Data Acquisition.....SDR

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