Coastal Flood Statement 3, NWS Key West, FL

Area Forecast Discussion
National Weather Service Key West FL
1045 PM EDT Fri Aug 2 2019

.SHORT TERM...
Since later afternoon, BYX radar has shown a boundary extending
southwest into the Straits from near Layton and Long Key.
Meanwhile, the air mass over the Lower Keys and Southeast Gulf was
worked over in the wake of heavy thunderstorms and then stratiform
rain that finally dissipated late this afternoon over the Gulf.
Dry Tortugas reported 4.85" of rain.

More recently, showers and thunderstorms have started firing off
along the boundary, with Long Key to Islamorada seeing the most
thunderstorm activity currently. Mesoscale models and very recent
radar trends show the boundary starting to spread northwest
toward the Lower Keys. This push and convergence along the
boundary will be aided by outflow of rain-cooled air spreading
out from the almost dissipated area of rain near the Cay Sal Bank.
Would expect further development along the boundary as low-level
convergence increases along it. Bottom line is this should
increase shower and thunderstorm development late this evening and
overnight for much of the Lower Keys. Will therefore hang on to
the likely PoPs.

The air mass will be supportive, given the 00z KEY sounding
observing a very moist Precipitable Water value of 2.12". The SPC
Sounding Climatology shows this near the 90th percentile for
moistness, compared to other soundings on this date in past years.

&&

.COASTAL FLOODING...
Today's tides around mid-day topped out around 0.3 feet above
criteria for minor tidal overflow. This was made possible by
spring tides with the recent New Moon and then an anomaly of about
0.8 feet above astronomical predictions. This led to saltwater
flooding of more flood-prone low-lying areas.

For Saturday, the astronomical prediction is 0.1 feet lower. If
tidal anomalies remain the same, then high tides around mid-day
would again exceed our criteria for minor tidal overflow. This
would require the later issuance of a Coastal Flood Statement. For
motorists, if you see a puddle in the road near a low-lying storm
drain, assume for the well-being of your vehicle that it is
saltwater. Avoid driving through the puddle and subjecting your
vehicle to saltwater exposure.

&&

.MARINE...
The main threat to mariners through Saturday will continue to be
above normal coverage of showers and thunderstorms, particularly
with the gusty outflow winds that accompany thunderstorms.

Otherwise, a surge of moderate southerly breezes is expected late
tonight and Saturday morning. Winds will then trend downwards late
Saturday, becoming variable on Sunday as an Atlantic high pressure
ridge builds across South Florida.

&&

.AVIATION...
VFR conditions will prevail at both EYW and MTH terminals.
Scattered showers and isolated thunderstorms are expected near the
island chain through the night and early morning hours, causing
brief periods of sub VFR conditions. Winds becoming S at 10
knots overnight.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&

Public/Marine/Fire...Haner
Aviation/Nowcasts....SDR
Data Collection......L. Kasper

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Hazardous Weather Outlook
National Weather Service Key West FL
450 AM EDT Fri Aug 2 2019

FLZ076>078-GMZ031>035-042>044-052>055-072>075-031000-
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-
450 AM EDT Fri Aug 2 2019

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

.DAY ONE...TODAY AND TONIGHT

Scattered thunderstorms, a few of which may be strong, are
expected along the Florida Keys and the surrounding coastal
waters today and tonight. The primary thunderstorm hazards will
be cloud to surface lightning strikes and strong gusty winds of 35
to 45 mph.

Due to above normal water levels, combined with high tides
associated with the new moon, minor saltwater flooding of low-
lying areas and streets is expected to occur around the time of
high tide from this morning into this afternoon.

In addition, locally heavy rainfall is possible along the Florida
Keys. This may cause localized ponding of water in low lying areas
and on roadways. Drainage of heavy rains will be further slowed
around the time of high tide.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

Isolated to scattered thunderstorms will be possible along the
Keys island chain and the surrounding coastal waters. The primary
thunderstorm hazards will be cloud to surface lightning strikes
and gusty winds.

Minor saltwater flooding of low-lying areas and streets is expected
to occur around the time of high tide again around midday
Saturday, and possibly early Sunday afternoon as well.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.