Special Marine Warning 331, NWS Miami, FL

Area Forecast Discussion
National Weather Service Miami FL
146 PM EDT Mon Aug 9 2021

.AVIATION(18Z TAFS)...
Hit or miss convection shifting inland for the afternoon and will
push westward towards APF and the Gulf coast. Some remnant
convection could linger around the terminals, particularly APF in
the evening. Bouts of sub-MVFR are possible if a terminal is
directly impacted by convection which could require short-fused
AMDs. Mainly easterly to southeasterly flow except at APF where
the Gulf sea breeze could turn the winds onshore during the
afternoon. Convection should diminish overnight with activity
increasing over the waters heading into sunrise.

&&

.PREV DISCUSSION... (Issued 1143 AM EDT Mon Aug 9 2021)

UPDATE...
Convective trend has been drier this morning with the general
forecast on track through the day. Made some minor tweaks to fit
PoPs, temps, and dewpoints through the early afternoon closer to
observed trends. 12z MFL sounding does have a cooler 500 mb temp
(around -7.1 deg C) and warmer temperatures at the lower levels,
which has produced steeper lapse rates. The concern for some
strong storms remains again today, focused inland and westward,
mainly fueled by the available instability and boundary
interactions. Strong wind gusts, frequent to excessive lightning,
and heavy rainfall are the primary concerns. There is a non-zero
threat of small hail. With the boundary interactions, some
localized shear could permit funnel cloud/landspout/waterspout
activity again today. Have a wonderful Monday!

PREV DISCUSSION... (Issued 351 AM EDT Mon Aug 9 2021)

SHORT TERM (Through Tuesday)...

South Florida remains under the continual presence of zonally
elongated ridging aloft. Meanwhile the western periphery of a broad
1000-850 hPa western Atlantic ridge continues to encompass the
region. This is allowing for east/southeasterly flow to preside
within this layer. Sufficient differential heating between the
interior and coastal regions should allow for sea-breeze circulation
development again today, which will remain the primary foci for
convection to spawn. The easterly flow will favor development along
interior and western portions of the region, particularly during the
afternoon/evening hours. PW around 2.0 inches, 500 hPa temperatures
near -7C, and instability on the order of roughly 3000-4000 J/kg of
surface-based CAPE will continue to support deep convection.
RAP forecast soundings indicate mid-level subsidence (around 700
hPa), which may somewhat inhibit the growth of storm cells compared
to days prior. Regardless, strong wind gusts, localized flooding,
and even small hail will possible in association with robust
thunderstorms that are able to develop today.  Very little deviation
in the region-wide forecast and associated impacts is anticipated
for Tuesday. The main concern will be localized and urban flooding
that could become realized across metro portions of Collier County -
should thunderstorms meander or redevelop over recently saturated
localities.

Muggy temperatures will continue across the region today, with
maximum temperatures in the upper 80s along the Atlantic coastline,
and lower 90s elsewhere. Dewpoints in the mid/upper 70s will allow
for apparent temperatures exceeding 100 in some locations. There
could be brief bouts of slightly cooler temperatures from storm
outflows and evaporative cooling processes.

LONG TERM (Tuesday Night through Sunday)...

Surface and middle tropospheric ridging is forecast to prevail
through mid-week. A TUTT over the Bahamas to start the period is
forecast to drift westward over the Florida peninsula and possibly
into the eastern Gulf of Mexico sometime this weekend. Weak
subsidence ahead of the TUTT and the advection of a plume of dry mid-
level air could result in a slightly suppressed seabreeze regime
Wednesday and Thursday, but scattered storms are still expected and
should follow the typical evolution under east/southeasterly flow.

NHC is currently monitoring a couple of tropical waves in the south-
central Atlantic, with the more pronounced wave nearing the Lesser
Antilles. This wave will continue westward along the base of the low-
level ridge and should move into either the northern Caribbean or
southwestern Atlantic towards the end of the week. Whether this wave
will actually develop into a depression or storm is *highly*
uncertain at this time. Deterministic and ensemble guidance depict a
rather weak system likely due to the increased shear from the
aforementioned TUTT and the potential for some dry air intrusion
depending on the eventual track of the wave. At this time there's
decent confidence that the end of the week and early weekend could
be quite wet locally. Beyond that, folks should continue with their
typical level of tropical season vigilance and preparedness.

MARINE...

Light easterly to southeasterly flow will continue through much of
the week, as high pressure remains over the region. Sea-breezes will
allow for an onshore wind component along the coast in the
afternoons. Scattered showers and thunderstorms will be possible
today, mainly over the Gulf waters and Lake Okeechobee. Winds and
seas could be locally enhanced near thunderstorms that do develop
today.

&&

.PRELIMINARY POINT TEMPS/POPS...
Miami            80  91  80  91 /  30  40  30  50
West Kendall     79  92  78  92 /  30  40  30  50
Opa-Locka        79  92  78  91 /  30  40  30  50
Homestead        79  90  78  90 /  30  40  40  40
Fort Lauderdale  80  90  80  89 /  20  40  30  40
N Ft Lauderdale  80  90  80  90 /  20  40  30  40
Pembroke Pines   79  90  78  90 /  20  40  30  50
West Palm Beach  78  90  78  91 /  20  40  20  50
Boca Raton       79  90  79  91 /  20  40  30  40
Naples           76  92  76  92 /  30  60  30  60

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.
&&

Aviation...RAG

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Hazardous Weather Outlook for South Florida...UPDATED
National Weather Service Miami FL
1152 AM EDT Mon Aug 9 2021

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
100200-
Lake Okeechobee-Biscayne Bay-
Coastal waters from Jupiter Inlet to Deerfield Beach FL out 20 NM-
Coastal waters from Deerfield Beach to Ocean Reef FL out 20 NM-
Waters from Jupiter Inlet to Deerfield Beach FL from 20 to 60 NM-
Waters from Deerfield Beach to Ocean Reef FL from 20 to 60 NM
excluding the territorial waters of Bahamas-Glades-Hendry-
Inland Palm Beach-Metro Palm Beach-Coastal Collier-Inland Collier-
Inland Broward-Metro Broward-Inland Miami-Dade-Metro Miami-Dade-
Mainland Monroe-Coastal Palm Beach-Coastal Broward-Coastal Miami-
Dade-Far South Miami-Dade-
Coastal waters from Chokoloskee to Bonita Beach FL out 20 NM-
Coastal waters from East Cape Sable to Chokoloskee FL out 20 NM-
Waters from Chokoloskee to Bonita Beach FL from 20 to 60 NM-
1152 AM EDT Mon Aug 9 2021

...Scattered Thunderstorms Possible Today...

This hazardous weather outlook is for South Florida.

.DAY ONE...THIS AFTERNOON AND TONIGHT

Thunderstorms: Scattered to numerous thunderstorms will be possible
today, with the greatest coverage anticipated over the interior and
Gulf coast region. The primary threats will be locally strong wind
gusts, frequent lightning, and localized flooding.

Flooding: Localized flooding from heavy rainfall will be possible
today, mainly across metro portions of Southwest Florida.

Wind: A few storms could become strong and may be capable of
producing wind gusts around 45 mph.

Waterspouts: Waterspouts will be possible with showers and
thunderstorms.

Hail: Small hail cannot be ruled out with the strongest thunderstorms
that develop today.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

Scattered showers and thunderstorms will be possible through this
week, primarily over interior and western portions of South Florida.
Locally gusty winds, waterspouts, localized flooding, and frequent
lightning strikes may accompany robust thunderstorms.

The rip current risk may increase along the Atlantic beaches of
South Florida this week as easterly winds build across the area.

An unsettled pattern emerges late in the week as attention turns to
the tropics. It is still too early the determine impacts, if any, for
South Florida but the increasingly unsettled pattern could increased
the threat of flooding from excessive rainfall Friday through the
weekend.

.SPOTTER INFORMATION STATEMENT...

Widespread spotter activation is not anticipated, however individual
spotters are encouraged to report high wind, hail and flooding to
the National Weather Service forecast office in Miami.

For more information...visit the National Weather Service in
Miami website at www.weather.gov/miami.

RAG