Damaging Winds in Florida, September 19, 2016

Area Forecast Discussion
National Weather Service Miami FL
201 PM EDT Mon Sep 19 2016

.AVIATION...
With showers and storms developing over the region, have left VCTS
in most sites. KAPF looks as though it should be spared, as the
Gulf sea breeze has pushed through the area already. There could
be brief IFR with the heavy showers accompanying the storms.
Convection should wane in the evening hours, with mostly dry
conditions through the night and into tomorrow morning.

&&

.PREV DISCUSSION... /issued 833 AM EDT MON SEP 19 2016/

AVIATION...
With low pressure off the Carolina coast, the flow, while weak,
will try to favor a westerly direction, off the surface. However,
the sea breeze is forecast to develop along both coasts, which
will be the main driving factor of not only the wind, but also
convective development. Showers and thunderstorms are forecast to
gradually develop this morning, mainly along the coast, the
increase in coverage and push inland this afternoon. However,
there is uncertainty as to the strength of the Atlantic sea
breeze, so have kept VCTS in the TAFs for mainly the afternoon and
early evening hours.

UPDATE...
No significant changes to the forecast, other than attempting to
time convection across South Florida through the day today. The
PoPs remain largely unchanged for the 6 and 12 hour period, but
the 3 hour periods show a trend of convection closer to the
Atlantic coast early on, but pushing most of the activity inland
for the late afternoon. Have also adjusted sky cover to reflect
the mostly clear skies on satellite and in the obs this morning.

PREV DISCUSSION... /issued 435 AM EDT MON SEP 19 2016/

DISCUSSION...
At 4 AM EDT, doppler radar indicated some blips of light to moderate
showers around 60 miles east of Miami Beach. Otherwise, fairly
quiet conditions resided over land. The 00Z MFL sounding showed
3500 J/KG of most unstable CAPE, a slight increase compared to 24
hours ago. Light and variable winds were noted from the surface
up to around 400 mb, with stronger northeast winds aloft. The
light low level flow will allow for both the Atlantic and Gulf sea
breezes to develop during this afternoon. The small scale models,
including the HRRR and Hi- Res WRF, prog the sea breeze collision
to occur from western Miami- Dade county northward towards western
Palm Beach county. As reflected in the grids, this region should have
the highest chance of precip today. Some of these storms could
produce outflow boundaries which would act to spark new convection
over the east coast metro during the late afternoon or evening.
Waterspout potential over the coastal waters will be slightly
elevated due to the light wind profile and steeper lapse rates in
the lower levels. Otherwise, relatively warm 500 mb temps and high
freezing levels will limit the main storm hazards to frequent
cloud to ground lightning and brief wind gusts 35- 45 mph. By
tonight, with the loss of diurnal heating, greatest chances of
storms will reside over the Atlantic waters. A very similar
weather pattern will take shape on Tuesday and Wednesday, with
light flow and afternoon/evening showers and storms, mainly over
the interior.

Thursday into Friday models indicate a slight decrease in PW and the
reestablishment of deep easterly flow. This pattern should shift
afternoon convection back towards the western interior and Gulf
coast. By this weekend, flow will become light and variable with
another round of increasing moisture.

Near normal temperatures will occur this week with heat index
values mainly ranging from the upper 90s to around 100 degrees.

MARINE...
Outside of local sea breeze effects, winds will
generally be east to southeasterly at 10 knots or less over the
next few days with seas 3 feet or less. Isolated to scattered
showers and thunderstorms will be possible each day with locally
erratic winds and hazardous seas in and around thunderstorms.

AVIATION...
VFR conditions should prevail at all terminals through the late
morning hours, although some brief periods of MVFR cigs are
possible. VCTS periods with scattered thunderstorms developing
around the terminals is again anticipated this afternoon, with
possible periods of MVFR conditions under lowering cigs and
reduced vis during heavy downpours. VFR conditions should follow
during the evening hours, but there may be some lingering cells
around APF through midnight.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  75  91  76  90 /  50  50  50  40
Fort Lauderdale  77  90  78  90 /  50  50  40  40
Miami            77  91  78  91 /  30  50  40  40
Naples           77  90  77  89 /  10  40  20  40

&&

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

HAZARDOUS WEATHER OUTLOOK FOR SOUTH FLORIDA
NATIONAL WEATHER SERVICE MIAMI FL
354 PM EDT MON SEP 19 2016

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
201200-
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-
354 PM EDT MON SEP 19 2016

...SCATTERED THUNDERSTORMS THIS AFTERNOON AND EARLY EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORMS: SCATTERED THUNDERSTORMS ARE FORECAST DURING THE
AFTERNOON AND EARLY EVENING HOURS, WITH THE BEST COVERAGE OVER THE
INTERIOR AND ATLANTIC COASTAL AREAS. THE PRIMARY THREAT WILL BE
FREQUENT LIGHTNING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SCATTERED THUNDERSTORMS ARE POSSIBLE EACH AFTERNOON AND EVENING,
ESPECIALLY OVER INTERIOR AND WEST COAST METRO AREAS OF SOUTH
FLORIDA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

FOR MORE INFORMATION...VISIT THE NATIONAL WEATHER SERVICE IN
MIAMI WEBSITE AT WWW.WEATHER.GOV/MIAMI.