Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 011748
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
148 PM EDT Sat Oct 1 2016

.AVIATION...Trends in the short ranged models suggest showers
and thunderstorms developing late this afternoon along the east
coast metro areas moving westward into the interior this evening.
VCTS has been included to the east terminal`s forecast. The
storms that develop will move westward into APF late this
afternoon. Short fused amendments will likely be necessary to
handle IFR/LIFR vsbys from heavy rain or MVFR cigs with these
showers and storms. Any activity that develops tonight over the
Atlantic has the potential to make its way into the east coast
metro areas. SHRA has not been added at this time.

&&

.PREV DISCUSSION... /issued 1002 AM EDT Sat Oct 1 2016/

UPDATE...
The wet pattern looks to continue today, particularly over the
Atlantic waters and along the east coast metro. The upper level
low over the Great Lakes and its associated frontal boundary
draped down the eastern seaboard into Florida. The forecast
remains on track this morning with fresh zones sent a short while
ago. Over the southern Atlantic waters this evening, SCEC
headlines may be required with a bit of an easterly wind surge
possible tonight.

PREV DISCUSSION... /issued 757 AM EDT Sat Oct 1 2016/

AVIATION...
A lull from Atlantic convection over the terminals for the next
few hours will be possible this morning before a round of
late morning to afternoon convection kicks off. Short fused
amendments will likely be necessary to handle IFR/LIFR vsbys from
heavy rain or MVFR cigs with these showers and storms.

PREV DISCUSSION... /issued 552 AM EDT Sat Oct 1 2016/

UPDATE...
As of 550 AM EDT...Current forecast remains on track for today.
Only update is for the latest 5 AM advisory from the National
Hurricane Center, which now has Hurricane Matthew as a Category 4
hurricane with maximum sustained winds of 155 mph. Matthew
continues to move westward at 7 mph and is still expected to turn
north this weekend. For additional information, please see the
latest forecasts from the National Hurricane Center and the long
term section of the forecast discussion below.

PREV DISCUSSION... /issued 355 AM EDT Sat Oct 1 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 SATURDAY EVENING/...

As of 550 AM EDT...Scattered showers and thunderstorms have been
ongoing for much of the night over the local Atlantic waters and
into portions of the east coast metro and southern Miami-Dade
county. A few of these storms have been occasionally strong with
frequent lightning and brief gusty winds. This trend will continue
through daybreak, with the rest of South Florida expected to
remain generally dry.

Synoptically, an upper-level low remains situated over the Ohio
River Valley, with a stagnant frontal boundary draped across north-
central Florida. Earlier overnight, Hurricane Matthew reached Category
5 status, with maximum sustained winds of 160 mph and a central
pressure of 941 hPa making it the strongest hurricane in the
Atlantic basin since Hurricane Felix back in 2007.

For today, another round of scattered showers and thunderstorms is
expected primarily during the afternoon and evening hours after
early morning convection over eastern areas wanes. The flow will
continue to become more easterly, which will favor the best
chances for convection across the interior and Gulf Coast later
today. Despite the prevailing easterly flow, the Atlantic sea
breeze may have a hard time pushing inland until late in the
afternoon due to the flow being weak, which will allow for
additional isolated to scattered showers/storms in portions of
the east coast metro as well.

The 00z observed KMFL sounding revealed warmer 500 hPa temps of
around -7.5 C, but forecast temps are again between -7 and -9 C
for today. With these continued below normal midlevel temps,
another day of active weather will be possible. Some strong
storms, with a few perhaps reaching borderline severe limits will
be possible, with frequent lightning, gusty winds, small hail, and
locally heavy rain being the primary threats.

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 SATURDAY EVENING THROUGH MONDAY 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 near 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, with the greatest coverage over the interior and
Gulf Coast. 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 easterly flow, 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 /TUESDAY THROUGH FRIDAY/...

The long term period continues to remain highly uncertain and
dependent upon the evolution, strength, and track of Hurricane
Matthew including where the northward turn in the central
Caribbean occurs and its forward speed along its track. While the
latest forecast track cone from the National Hurricane Center
continues to remain east of greater South Florida, there continues
to remain much uncertainty in the track, with the 00z GFS slightly
further west and the 00z ECMWF slightly further east with many
ensemble members in between. The ultimate track will be
determined by the relative position of high pressure over the
western Atlantic, and the placement of upper-level lows over the
Gulf of Mexico and northeast CONUS.

At this time, the greatest threat period appears to be beginning
Tuesday, with the length of the threat period determined by how
fast Matthew`s forward speed is. Scattered showers and
thunderstorms will 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.

While there remains a great deal of uncertainty on potential impacts
of Hurricane Matthew for South Florida, a hurricane is likely to be
in or near the Bahamas by Tuesday, so all interest in South Florida
must remain alert. 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 beginning Tuesday 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 through the weekend for
all South Florida beaches. Increased rip current risk is likely
beginning early next week for Atlantic beaches along with other
possible hazardous conditions such as significant waves, coastal
flooding, and beach erosion as Hurricane Matthew moves closer to
the region.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  80  90  79  89 /  40  50  30  50
Fort Lauderdale  81  89  80  87 /  50  50  40  50
Miami            80  89  79  88 /  50  50  40  50
Naples           77  91  76  90 /  40  60  30  60

&&

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

$$

AVIATION...67/MT



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