Area Forecast Discussion
Issued by NWS Miami, FL

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000
FXUS62 KMFL 301209
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
809 AM EDT Fri Sep 30 2016

.AVIATION...
VFR conditions will prevail through early this afternoon with
mainly clear skies. Both the Gulf Coast and east coast sea breeze are
expected to develop by around 30/1700Z. Showers and thunderstorms,
initiating by early afternoon should periodically affect all TAF
sites through 01/0100Z. Some storms may become strong, capable of
producing gusty and erratic winds over 30KT and decrease vis to
below 3 sm in RA+. Activity will wane overnight, with VFR conds
returning.

&&

.PREV DISCUSSION... /issued 348 AM EDT Fri Sep 30 2016/

DISCUSSION...

SYNOPSIS...

An upper-level low over the Ohio River Valley and frontal boundary
over northern Florida will continue to promote scattered showers and
thunderstorms through the weekend as plenty of tropical moisture
remains in place across the region.

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

As of 345 AM EDT...Mainly dry weather has been ongoing across
much of South Florida early this morning, outside of some widely
scattered showers and thunderstorms over the Gulf waters. This
trend is expected to continue through daybreak, with another round
of scattered showers and thunderstorms expected later today, with
much of the morning continuing to remain dry for most.

The flow will continue to be out of the south/southwest, which will
help to limit the inland extent of the Atlantic sea breeze and favor
a stronger Gulf breeze. By the late morning/early afternoon hours,
scattered showers and thunderstorms should develop along the leading
edge of the Gulf sea breeze, progressing inland into the afternoon
hours. Some storms will also be possible in the east coast metro
area as well as the Atlantic sea breeze struggles to push inland.

The observed 00z KMFL sounding indicated a 500 hPa temp of -9.4 C,
which is near the coldest observed temps at this level for this time
of year. Forecast model soundings for this afternoon and evening
continue to show 500 hPa temps hovering around -9 C, which would
likely yield midlevel lapse rates around -7 C. Therefore, a few
strong to perhaps severe storms with gusty winds and small hail will
certainly be a possibility today and will highlight this threat in
the Hazardous Weather Outlook. With plenty of tropical moisture in
place and relatively slow storm motion, locally heavy rainfall will
also be a concern, with localized poor drainage flooding possible in
urbanized and low lying areas.

High temperatures will generally be in the upper 80s across the
region today, with a few lower 90s readings possible in the interior.

SHORT TERM /6 PM FRIDAY EVENING THROUGH SUNDAY NIGHT/...

The upper-level low over the Ohio River valley and lingering frontal
boundary across northern Florida will continue to promote an
unsettled weather pattern through the weekend across the region.
Deep tropical moisture will continue to remain in place and continue
to advect into the region ahead of Hurricane Matthew, likely
remaining at or above 2.0 inches through the period, above normal
for this time of year. Coupled with mesoscale effects like sea
breeze and outflow convergence, scattered to locally numerous
thunderstorms are expected especially during the afternoon and
evening hours. During the night, convection is expected to decrease
over land and remain focused over the local waters, with a few
showers and storms occasionally impacting portions of the east coast
metro area.

With the flow gradually transitioning to more of an easterly
direction, the greatest coverage should be across the interior and
Gulf Coast, although the east coast metro area will see chances for
storms during the late morning and early afternoon hours as well.
Forecast 500 hPa temps in the -7 to -9 C range could also lead to
some locally strong storms during the short term period as well.
High temperatures will generally be in the 80s with low temperatures
in the 70s.

LONG TERM /MONDAY THROUGH THURSDAY/...

The long term period continues to remain highly uncertain and
dependent upon the evolution, strength, and track of Hurricane
Matthew. While there continues to remain significant uncertainty on
potential impacts for land areas, confidence continues to increase
that marine conditions will deteriorate and become hazardous
early next week, possibly continuing through most of the week.

Regardless, scattered showers and thunderstorms will certainly be
possible through the long term period, with the eventual track of
Matthew ultimately determining the areal coverage of convective
activity. It will likely be breezy at times as well during the long
term period, especially along the east coast. High temperatures will
generally be in the mid to upper 80s with low temperatures in the
70s.

While there remains a great deal of uncertainty on potential impacts
of Hurricane Matthew for South Florida, now is the time to review
hurricane preparedness plans and to make sure your hurricane
supplies are fully stocked. Interests in South Florida should
continue to remain well informed on the forecast regarding Hurricane
Matthew with the latest information from the National Hurricane
Center and National Weather Service Miami.

MARINE...

Scattered showers and thunderstorms will be possible through the
weekend, especially over the local Atlantic waters as the flow
gradually shifts to an easterly direction.

As Hurricane Matthew tracks closer to the region early next week,
hazardous marine conditions will be possible, with conditions
expected to deteriorate early next week and continuing through
much of the week. Hazardous seas and gusty winds will be possible,
with the magnitude ultimately dependent on the evolution,
strength, and track of Matthew.

Marine interests should continue to remain well informed on the
latest forecasts from the National Hurricane Center and National
Weather Service Miami.

BEACH FORECAST...

Rip current risk is expected to remain low today for all South
Florida beaches. Rip current risk along Atlantic beaches may
increase late this weekend as Hurricane Matthew moves closer to the
region. Increased rip current risk will likely continue through much
of next week for Atlantic beaches along with other possible
hazardous conditions such as significant waves and beach erosion.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  90  77  89  78 /  50  40  50  30
Fort Lauderdale  90  78  89  78 /  50  40  50  40
Miami            89  77  90  78 /  50  30  50  30
Naples           89  75  91  75 /  40  30  60  30

&&

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

$$

DISCUSSION...92/IRL
MARINE...92/IRL
AVIATION...27/JT



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