Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 270754
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
354 AM EDT SAT AUG 27 2016

.SYNOPSIS...

A broad upper-level ridge will remain established across the
Southeast CONUS through the weekend along with high pressure at the
surface. A strong tropical wave will track near the region this
weekend and into early next week with unsettled weather.

&&

.DISCUSSION...

NEAR TERM /THROUGH 6 PM SATURDAY EVENING/...

...Moderate Risk of rip currents for Atlantic beaches today...

As of 350 AM EDT...A broad upper-level ridge remains firmly
entrenched across the Southeast with surface high pressure over the
Mid-Atlantic and a tropical wave across the central Bahamas. A
very moist tropical airmass remains in place across South Florida,
with PWAT values around 2.3 inches well above normal - above the
90th percentile for this time of year.

With the combination of the approaching tropical wave and abundant
tropical moisture, unsettled weather is expected across most of
South Florida with scattered to locally numerous showers and
thunderstorms today, with the best chance this afternoon and
evening. Frequent lightning and locally heavy rainfall will be
the primary threats. Where locally heavy rainfall occurs, poor
drainage flooding will be possible, especially in urbanized areas.
The tropical airmass will continue to make it feel quite muggy and
humid, with high temps around 90 for most areas and heat indices
100-105 degrees.

With increasing northeasterly/easterly flow across the region,
there will be a Moderate Risk of rip currents for the Atlantic
beaches today. Depending on the strength of the onshore flow
today, a High Risk may need to be issued for the Atlantic beaches
and will continue to mention this in the Hazardous Weather Outlook.

SHORT TERM /6 PM SATURDAY EVENING THROUGH MONDAY NIGHT/...

...Tropical wave to bring periods of locally heavy rain and
breezy conditions Sunday and into Monday...

...Increased risk of rip currents for Atlantic beaches continuing
into Sunday...

The main weather story for Sunday and into Monday continues to be
the westward progress of a strong tropical wave/Invest 99L across
the region. The latest National Hurricane Center Tropical Weather
Outlook valid at 2 am places the tropical wave near the central
Bahamas, with a 20% chance for development in the next 2 days and
now a 40% chance of development over the next 5 days.

While there still remains uncertainty with potential development of
this system, forecast confidence is increasing in the following two
areas:

1. Tropical cyclone development is becoming increasingly less likely
for the tropical wave as it moves past South Florida, with
conditions still somewhat favorable as the wave moves into the open
Gulf of Mexico.

2. The track of the tropical wave will likely be south of South
Florida and through the Florida Straits.

Despite these factors, the tropical wave will still have a
significant influence on South Florida weather especially Sunday and
into Monday, with the main threats being locally heavy rainfall with
scattered to numerous showers and thunderstorms. A few squalls may
also be possible as well over the local Atlantic waters.

The best chance for more widespread coverage looks to be Sunday
night into Monday, with better synoptic lift on the east side of the
passing wave. Forecast rainfall could be on the order of several
inches, leading to possible flooding concerns. Antecedent soil
moisture may play a big role in potential flooding as well, with
much of South Florida outside of interior regions near Lake
Okeechobee near or slightly below normal which could help offset
potentially higher rainfall amounts. Nevertheless, poor drainage
flooding will be a possibility especially in the east coast metro
area.

The amount of rainfall across the region will be highly dependent on
the track of the tropical wave, with the highest confidence for
higher rainfall amounts at this time across far southern areas.

Regardless of exact rainfall totals, the tropical airmass will
remain firmly entrenched across the region with extended periods of
cloudy skies and breezy conditions in addition to the occasional
showers and thunderstorms.

There will also be at least a Moderate Risk of rip currents for
Atlantic beaches continuing into Sunday, with the potential for
High Risk. An increased risk of rip currents will also be
possible on Monday as well, but will ultimately depend on the
track of the tropical wave and resulting flow in its wake.

While tropical cyclone development appears unlikely for South
Florida, residents and visitors to South Florida should continue to
closely monitor the products of the National Hurricane Center and
National Weather Service in Miami over the next few days to stay
alert for any potential impacts to South Florida with this system.
The forecast will continue to be adjusted with the latest model
guidance.

LONG TERM /TUESDAY THROUGH FRIDAY/...

Despite the passage of the tropical wave/Invest 99L, it will
continue to remain unsettled across South Florida for much of the
week. Scattered to numerous showers and thunderstorms will be
possible each day, especially during the afternoon and evening
hours. The tropical airmass will remain in place, with plenty of
moisture across the region.

Locally heavy rainfall may continue to remain a threat, and will
continued to be monitored closely over the upcoming days, but will
be highly dependent based on the eventual track of the tropical
wave. The latest model guidance continues to show the upper-level
ridge over the Southeast flattening out, with an upper-level trough
potentially digging southward from the Great Lakes region by the end
of the week. The evolution of the upper-level pattern will have a
significant influence on the track of the tropical wave and
resulting flow across South Florida for the midweek period and
beyond.

If the wave curves and tracks north into the northern Gulf
of Mexico, flow will be more southerly enhancing rainfall potential,
with a more westward track through the Gulf possibly favoring a
return to more of a typical easterly summer-like pattern.

Rip current risk may continue to be increased at least through
midweek, but highly dependent on the flow that sets up in the wake
of the tropical wave.

&&

.MARINE...
Northeast to easterly flow will prevail over the local Atlantic
and Gulf waters today, then veering to a more easterly flow
through the rest of the weekend. Winds will generally be 10-15
knots, increasing to 15-20 knots by Sunday. Seas will increase to
3-6 feet over the local Atlantic waters with an easterly swell of
1-2 feet, and 2-4 feet over the local Gulf waters for this
weekend. Scattered to numerous thunderstorms will continue through
early next week, with rough seas and locally gusty winds with any
thunderstorm that forms.

There continues to remain considerable uncertainty for winds and
seas late this weekend and into early next week as a tropical
wave near the central Bahamas moves closer to the area. Please
consult the products of the National Hurricane Center and our
latest forecasts for additional information.

&&

.AVIATION...
The winds will remain easterly today with speeds of 5 knots or
less early this morning increasing to 10 to 15 knots after 14Z
today over the east coast taf sites. For APF taf site...the winds
will also remain easterly at 5 knots or less early this morning
increasing to 5 to 10 knots after 14Z today. The weather will
remain dry at KAPF taf site until 14Z, then VCSH until 18Z
followed by VCTS for the afternoon hours. For the east coast taf
sites, VCSH will remain in the taf sites until 14Z then VCTS for
the afternoon hours. The ceiling and vis will remain in the VFR
conditions today at all of the taf sites. However, the ceiling and
vis could fall down into MVFR or even IFR conditions with any
passage of showers or thunderstorms.

&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  91  81  90  78 /  50  40  70  50
Fort Lauderdale  90  80  88  78 /  50  50  70  70
Miami            92  78  89  77 /  50  60  70  70
Naples           92  77  91  77 /  60  30  60  50

&&

.MFL Watches/Warnings/Advisories...
FL...None.
AM...None.
GM...None.
&&

$$

SYNOPSIS/DISCUSSION/MARINE...92/IRL
AVIATION...54/BNB



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