Areal Flood Advisory 10, NWS Key West, FL

Area Forecast Discussion
National Weather Service Key West FL
1106 AM EST Thu Nov 18 2021

.DISCUSSION...
Water vapor imagery highlights a long wave trough from James Bay,
southwest to the Eastern Pacific. A splattering of PDVA continues
to pulse to the northeast across the Gulf of Mexico, invigorating
fractured baroclinic boundaries. One of these boundaries is moving
north towards the Keys this morning, with healthy thunderstorms
embedded along the line. Surface winds are backed to the northeast
north of the line, maintaining a robust zone of confluence and
moisture convergence.

The 12Z KKEY RAOB sampled more than 2.0" of PW, meager deep layer
shear, and respectable low level helicity. The autumnsky KBYX
hodograph has measured 0-3km shear as high as 190 m2/s2, probably
aided by the mesoscale backing of the winds along the island
chain. No wonder we continue to detect occasional circulations
south of the island chain. The cooler waters near the island
chain should limit the effective BL fuel for these cells as they
near the island chain. We issued an earlier update to increase
rain/thunder chances to 90%, and we held onto the Small Craft
Advisory for one more cycle. Given the widespread convection, we
did not want to send the wrong message by canceling the Advisory
to announce an all clear, because it is every bit of nasty across
the Florida Keys this morning.

Satellite derived TPW loops from CIMSS place a pipe of very dry
low-level air across Cuba, which should work to the northwest this
afternoon, eventually decreasing coverage of showers and storms
across the Straits, and then locations near the island chain.

&&

.MARINE...
Small Craft Advisory remains in effect for Hawk Channel and the
Straits of Florida due to northeast to east winds near 20 knots.
The Advisory is despite the large expanse of strong thunderstorms
across the Atlantic- side waters. Winds and seas should diminish
this afternoon as the storms lose their intensity.

High pressure centered over the western Atlantic to the north of
Bermuda will continue to shift eastward today and tonight as a
cold front advances through the eastern United States and into the
Florida peninsula. Across the Keys coastal waters, fresh to
strong easterly breezes early this morning will diminish quickly
later today, with light breezes tonight becoming gentle to
moderate from the northeast on Friday, then fresh on Friday night,
as the front stalls over central Florida and strong high pressure
moves across the Ohio Valley. Breezes will become light on
Sunday, then turn to the northwest and begin to increase on Monday
as a strong cold front approaches. This front is forecast to
blast through the Keys waters Monday night, bringing strong
northerly breezes.

&&

.AVIATION...
Numerous showers and isolated thunderstorms will continue to move
across both terminals through the afternoon. Due to the lower
confidence in timing and location of any thunder, have omitted any
mention of VCTS for the time being. TEMPOs are currently in place
for the activity currently passing across each terminal and these
TEMPOs will likely need to be extended to account for the showers
and thunderstorms upstream. Sub-VFR conditions will likely
prevail through the early afternoon in this activity. Winds will
generally be from the northeast to east at 8 to 12 knots outside
of convection.

&&

.CLIMATE...
On this day in 1951, the daily record cold high temperature of 66F
was last recorded in Key West. Temperature records date back to
1872.

&&

.PRELIMINARY POINT TEMPS/POPS...
Key West  80  74  81  73 / 90 60 50 40
Marathon  80  74  81  73 / 90 60 50 40

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...Small Craft Advisory for GMZ042>044-052>055-072>075.

&&

Public/Marine/Fire...CLR
Aviation/Nowcasts....NB
Data Acquisition.....SMS

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Hazardous Weather Outlook
National Weather Service Key West FL
427 AM EST Thu Nov 18 2021

FLZ076>078-GMZ031>035-042>044-052>055-072>075-191000-
Monroe Upper Keys-Monroe Middle Keys-Monroe Lower Keys-
Florida Bay including Barnes Sound, Blackwater Sound, and
Buttonwood Sound-
Bayside and Gulf side from Craig Key to west end of Seven Mile
Bridge-
Gulf waters from East Cape Sable to Chokoloskee 20 to 60 NM out
and beyond 5 fathoms-
Gulf of Mexico including Dry Tortugas and Rebecca Shoal Channel-
Gulf of Mexico from west end of Seven Mile Bridge to Halfmoon
Shoal out to 5 Fathoms-
Hawk Channel from Ocean Reef to Craig Key out to the reef-
Hawk Channel from Craig Key to west end of Seven Mile Bridge out
to the reef-
Hawk Channel from west end of Seven Mile Bridge to Halfmoon Shoal
out to the reef-
Straits of Florida from Ocean Reef to Craig Key out 20 NM-
Straits of Florida from Craig Key to west end of Seven Mile
Bridge out 20 NM-
Straits of Florida from west end of Seven Mile Bridge to south of
Halfmoon Shoal out 20 NM-
Straits of Florida from Halfmoon Shoal to 20 NM west of Dry
Tortugas out 20 NM-
Straits of Florida from Ocean Reef to Craig Key 20 to 60 NM out-
Straits of Florida from Craig Key to west end of Seven Mile
Bridge 20 to 60 NM out-
Straits of Florida from west end of Seven Mile Bridge to south of
Halfmoon Shoal 20 to 60 NM out-
Straits of Florida from Halfmoon Shoal to 20 NM west of Dry
Tortugas 20 to 60 NM out-
427 AM EST Thu Nov 18 2021

This Hazardous Weather Outlook is for the Florida Keys and
adjacent coastal waters.

.DAY ONE...TODAY AND TONIGHT

A Small Craft Advisory is in effect this morning for Hawk Channel
and the Straits of Florida, due to east winds near 20 knots, and
seas up to 7 feet in the Straits of Florida. Winds are expected
to decrease below 20 knots later this morning, and decrease
further this afternoon.

Isolated thunderstorms are expected today and tonight. The main
hazards will be lightning and locally gusty winds.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

Isolated thunderstorms will be possible on Friday. The main
hazards will be lightning and locally gusty winds.

A Small Craft Advisory may be required for parts of the Keys
coastal waters on Friday night into Saturday.

A strong cold front is forecast to blast through the Keys coastal
waters Monday night, with Small Craft Advisories likely needed
for all waters for Monday night and Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.