Areal Flood Advisory 5, NWS Key West, FL

Area Forecast Discussion
National Weather Service Key West FL
1229 AM EDT Fri Aug 13 2021

.DISCUSSION...
KBYX is currently detecting scattered to numerous showers across
the island chain and surrounding coastal waters. This convective
activity is capitalizing on the sharp increase in CAPE since this
morning and the negligible inhibition. Steep surface to 3 km lapse
rates were recorded by this evening's sounding, as well as drier
air aloft. All of this, combined with the fast motion of these
storms, has led to very squally weather. Earlier this evening,
the Weatherflow mesonet site at Smith Shoal Light recorded a wind
gust of 49 knots in what seemed like a smaller shower. All of the
island chain has received measurable rainfall over the past few
hours, which has led to temperatures ranging between near 80
degrees and the lower 80s. Outside of convection, breezes are
moderate out of the northeast to east. CIMSS MIMIC TPW shows
enhanced moisture currently moving into our area, so have nudged
PoPs up to likely/numerous for the rest of the night.

Tropical Depression Fred is currently struggling to regain
strength after moving across the mountainous terrain of
Hispaniola. This is due to the near 20 knots of southwesterly
shear that is being produced by an upper-level low currently atop
north central Florida. Looking ahead to tomorrow, winds will start
to gradually increase as Tropical Depression Fred moves closer to
the Florida Keys and begins to enhance the pressure gradient
across the region. The subtropical ridge that is currently
extending across the southeastern U.S. will continue to steer the
system to the west northwestward towards the Florida Keys prior to
a turn to the northwest as it moves past our area. Model guidance
deviates somewhat on the evolution of the previously mentioned
upper-level low. Some guidance has the low a little stronger and
shifting to over the Gulf, while the other solution has it a
little less strong. This will determine how much strengthening
this system will be able to do over the next day or two, depending
on the amount of shear that continues to impact the system. Fred
is still expected to become a tropical storm again as it moves
across the Straits of Florida. Squally weather will be the
precursor to the system, which will cause hazardous marine
conditions prior to the arrival of the storm. The earliest
reasonable timing is Friday night, while the most reasonable time
is Saturday morning. The timing of Fred's arrival has is slightly
later due to the system slowing down. Fred is expected to exit
the offshore Gulf Waters during the day on Saturday.

As Fred moves farther away from our area, the pressure gradient
will slacken and allow winds to decrease. Enhanced moisture will
linger through the extended forecast, so have kept above normal
rain chances. Ridging will build back into the area at the
beginning of next week. Another tropical wave is on the heels of
Fred, however, high uncertainty remains with this system. Details
will be refined over the next few forecast cycles.

&&

.MARINE...
A Tropical Storm Watch is in effect for all coastal waters aside
from the far western Straits of Florida. High pressure extending
from the western Atlantic into the southeastern United States will
maintain moderate northeast to easterly breezes across the
coastal waters of the Florida Keys for the remainder of the night.
Breezes will begin to freshen Friday as Tropical Depression Fred
approaches. Hazardous marine conditions are expected Friday night
through Saturday night, featuring strong northeast breezes
shifting to the southeast to south as Fred moves through Keys
waters and into the southeastern Gulf of Mexico. Winds will be
higher in thundery squalls. Locally heavy rainfall is possible as
Fred approaches and passes through the Keys. Make sure bilge pumps
are in proper working order and scuppers are free of debris.

&&

.AVIATION...
VFR conditions have returned to both island terminals and will
persist through the remainder of the overnight. Much of the showers
and thunderstorms have waned and will expect a break here through at
least sunrise. Squally weather looks likely after 15Z Friday. That
said, a few isolated showers will be possible overnight but not
expecting impacts at this time.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...Tropical Storm Watch for FLZ076>078.

GM...Tropical Storm Watch for GMZ031>035-042>044-052>054-072>074.

&&

Public/Marine/Fire...NB
Coordinator/Hazards...Jacobson
Aviation/Nowcasts....LIW/CLR
Data Acquisition.....DR/AP

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Hazardous Weather Outlook...UPDATED
National Weather Service Key West FL
932 PM EDT Thu Aug 12 2021

FLZ076>078-GMZ031>035-042>044-052>055-072>075-131015-
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-
932 PM EDT Thu Aug 12 2021

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

.DAY ONE...TONIGHT

Scattered thunderstorms are expected tonight. The primary
thunderstorm hazards will be cloud to surface lightning strikes
and localized wind gusts 40 to 50 mph.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

Tropical Depression Fred is forecast to move west northwest along
the north coast of Cuba and regain minimal tropical storm
intensity tonight and Friday, then move northwest through the
Florida Straits and the Florida Keys into the southeastern Gulf of
Mexico as a tropical storm Friday night and Saturday. The main
threat for adverse weather impacts from Fred will occur from
Friday evening through Saturday evening, including tropical storm
force winds, especially in frequent squalls, very hazardous marine
conditions, isolated tornadoes, and minor coastal flooding.

Heavy rainfall will be possible from Friday through Sunday, with
multi-day rainfall totals of 3 to 6 inches with isolated maximum
totals up to 8 inches. There will be a significant potential for
flooding of streets and poor drainage areas, especially during the
times of high tide in the pre-dawn hours of Saturday and Sunday
mornings.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

CLR

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE KEY WEST FL
1114 PM EDT THU AUG 12 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1036 PM     MARINE TSTM WIND 14 NW KEY WEST          24.72N 81.92W
08/12/2021  M44 MPH          GMZ033             FL   MESONET

            AN EAST-NORTHEAST WIND GUST OF 38 KTS, OR 44 MPH, WAS
            RECORDED BY THE WEATHERFLOW MESONET SITE AT SMITH SHOAL
            LIGHT AT 1036 PM EDT.

&&

AP