Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 261315 AAA
AFDMFL

Area Forecast Discussion...UPDATED
National Weather Service Miami FL
915 AM EDT Wed Apr 26 2017

.UPDATE...
Main change to the forecast is to slightly increase rain chances
across Miami-Dade and Broward counties to 30% this afternoon.
Mid-level shortwave trough over the eastern Gulf of Mexico this
morning depicted well by both operational GOES and experimental
GOES-16 data, along with an upper level subtropical jet maxima
extending west/east across the Gulf and South Florida. In the
low-levels, satellite imagery indicating enhanced cumulus clouds
over the Straits of Florida, suggesting a low level boundary which
is setting off a few showers south of the Keys. This roughly
depicts the area of deeper moisture in SE/S wind flow which will
surge north across the southern Florida peninsula this afternoon.
This morning`s sounding from Key West already shows this moisture
increase compared to drier low levels in the Miami sounding data.
These conditions expected to be in place over South Florida this
afternoon, along with low level convergence from sea breezes and
upper level divergence from subtropical jet, should support
scattered showers over the eastern half of South Florida,
particularly Miami-Dade and Broward counties as indicated above.
Mid-level cap/inversion looks to remain in place with dry air
above, which should limit if not totally prevent any deeper
convection/thunderstorm development.

Also modified dewpoint/humidity values slightly to account for
slightly higher moisture for the east coast metro areas, with
little change over the interior where the greatest fire weather
concern exists. Net result in those areas is lowest relative
humidity values in the lower 40s, above critical levels.
Therefore, no Red Flag Warning needed at this time and will
continue to monitor trends closely.

&&

.PREV DISCUSSION... /issued 733 AM EDT Wed Apr 26 2017/

AVIATION...
VFR conditions to prevail today as winds become SE/S later this
morning and this afternoon, but lacking deep enough moisture for
widespread lower ceilings. Most ceilings today expected in the
040-050 range. Mid/upper level shortwave moving across Florida
today will help produce a few showers over the eastern half of
South Florida this afternoon, but activity not expected to be
widespread enough to include in TAFs at this time. Light/variable
winds early this morning will become 140-150 degrees at 8-12 knots
between 15z-17z and remain that way through 00z, except a
seabreeze shift to 190-200 at KAPF by 18z.

PREV DISCUSSION... /issued 339 AM EDT Wed Apr 26 2017/

.Showers possible over inland portions of South Florida this
afternoon...

DISCUSSION...
Atlantic high pressure has settled over South Florida, with
generally light winds and little cloud cover this morning. The
southeasterly flow will allow some moisture to push over the
region today which could allow for some showers to develop this
afternoon as a mid-level trough pushes across South Florida.
Currently, shower development chances look best over western
portions of the east coast metro and over the Everglades. Areas
along and west of US 27 in Palm Beach and Broward Counties or
west of the Homestead Extension of Florida`s Turnpike in Miami-
Dade County look to have slightly better rain chances than areas
closer to the coast today. High resolution guidance is hinting
that some areas could see the potential wetting rains if showers
do develop as they should be pretty slow moving thanks to the
light southeasterly flow promoted by the high.

As today concludes, any convection should diminish through the
evening and a quiet and slightly warmer night should ensue. The
southeasterly flow will persist through much of the week allowing
for a taste of summer to take over South Florida. Temperatures in
the low 90s will prevail but without the relief of afternoon
showers and thunderstorms. The next frontal system will fizzle out
before reaching South Florida Thursday, with deep layered high
pressure building over the state on Friday. This high will persist
through the weekend until the next front emerges early next week.
As the front enters the region on Monday, rain shower chances will
increase and the potential for thunderstorms returns to the
forecast. This system may be the first chance for a widespread
wetting rain, but we are still quite far out in the extended
forecast period to state anything too definitively at this point.

MARINE...
Light southeasterly flow is expected across the waters over the
next several days with the potential for showers. Seas should
remain below headline criteria through the most of the week save
for some overnight wind surges possible in the Atlantic.

FIRE WEATHER...
While today is not expected to be as dry as previous days, there
remains a chance for a few hours of relative humidity values
nearing the critical 40 percent threshold over portions of
interior Southwest Florida including in Glades, Hendry, and inland
Collier County. At this point, the wind speeds do not look to
support Red Flag Conditions and the amount of time forecast to see
relative humidity values at or below 40 percent is an hour or two.
A short-fused Red Flag Warning may become necessary if observed
trends during the morning and afternoon hours skew drier or
windier than forecast. Will allow the day shift to monitor the
situation further.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  84  75  90  76 /  20  20  10  20
Fort Lauderdale  85  76  89  79 /  20  20  10  10
Miami            83  75  90  78 /  30  20  10  10
Naples           85  71  89  73 /  10  10  10  10

&&

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

UPDATE...59/Molleda


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