FXUS62 KMFL 171732 AAC

Area Forecast Discussion...UPDATED
National Weather Service Miami FL
132 PM EDT Tue Jul 17 2018

The east and west coast sea breezes have developed early this afternoon.
The west coast sea breeze will continue to push east across South Florida,
while the east coast sea breeze remains just west of the east coast
taf sites. Therefore, the east coast taf sites will remain southeast
around 5 to 10 knots this afternoon, as KAPF taf site remains westerly.
The winds will become light and variable tonight at all of the taf
sites. Showers and thunderstorms are developing along the sea breezes
and should continue through the afternoon hours. Therefore, VCTS
will continue for the east coast taf sites through 23Z, but KAPF
will remain dry for the afternoon hours. All of the taf sites should
remain dry tonight. The ceiling and vis will remain in VFR conditions
tonight, but could drop down into MVFR or even IFR conditions with
the passage of showers or thunderstorms for the east coast taf sites
this afternoon.


.PREV DISCUSSION... /issued 1024 AM EDT Tue Jul 17 2018/


The mid to upper level trough will continue to move east from the
Central United States into the Eastern United States today into
tonight. This will allow for the ridge of high pressure to shift
southward into the Bahamas and extend into South Florida allowing
for the steering flow to be more south southwest today over the
area. This in turn will allow for the west coast sea breeze to
push eastward across South Florida while the east coast sea breeze
remains near the western metro areas of the east coast.
Therefore, showers and thunderstorms should develop along both
sea breezes this afternoon with the best coverage over the eastern
interior areas and over Palm Beach County.

The Saharan Dust over the Florida Straits and Cuba will also move
slowly northward today and should move into South Florida this
evening into tonight replacing the tropical air currently over
the region. This will allow for a few of the thunderstorms late
this afternoon into this evening to become strong with gusty winds
and possible small hail especially where the sea breezes collide,
as the mid levels of the atmosphere dries out and cools a little

Rest of the forecast looks good at this time and no other changes
are planned.


PREV DISCUSSION... /issued 722 AM EDT Tue Jul 17 2018/

The winds will be light and variable this morning over all of the
taf sites, before going 150 to 160 degrees over the east coast
taf sites, and southwest at KAPF taf site this afternoon. The
steering flow will be south to southwest today, focusing the
showers and thunderstorms over the east coast taf sites.
Therefore, VCTS has been added for the east coast taf sties
between 18 and 00Z today and chance VCTS to VCSH for KAPF taf
site. The ceiling and vis will remain in VFR conditions outside of
any showers or thunderstorms, but could fall into MVFR or even
IFR conditions with the passage of showers and thunderstorms.


PREV DISCUSSION... /issued 406 AM EDT Tue Jul 17 2018/

The weather pattern will consist of a potent trough moving into
the Great Lakes region and a broad upper ridge over the Desert SW.
The trough axis will slightly deepen across much of the eastern
U.S. this week while a subtropical ridge over the Western Atlantic
gradually strengthens across South FL. Precipitable water values
above 2+ inches remain concentrated with this trough towards the
FL panhandle. Over South Florida, drier air approaches the area as
the high pressure builds with some SAL making it into the region.
Lower POPs continue through Thursday each afternoon with the best
chance over the interior and east coast metro areas.

As surface ridge makes its way into South FL, the south to southeast
steering flow will veer southwest for the remainder of the week, so
any mid-afternoon storms that form would move toward the ne part of
South FL for late afternoon while remaining drier to the w. The heat
index values through Wednesday are forecast to be as high as 106 for
the western half of Collier County, Mainland Monroe and inland Miami-
Dade over the Everglades. Heat index values are also forecast to
reach 106 for portions of metro Palm Beach County today-Wednesday.

Next weekend, forecast will depend on how much and how quickly
the ridge breaks down, if at all. There is still significant
uncertainty as to if and when the trough to our north will move
southward. It appears that the chance of the ridge breaking down
will gradually increase. This means that moisture and POPs could
increase over the weekend.

The western Atlantic ridge will gradually build westward this
week, with prevailing flow remaining southerly today then
becoming southwest later in the week. The increasing pressure
gradient will bring speeds up to 10 knots over the Gulf and 10-15
knots over the Atlantic, still light enough to allow both the Gulf
and Atlantic seabreezes to develop each afternoon. Seas generally
2 ft or less, occasionally 3 feet in the Atlantic. Showers and
storms will be a concern for all the waters through the period,
though coverage should generally be below normal. Locally higher
winds and seas are possible near any storms.

VFR and light winds prevail through the late morning hours.
Thereafter, scattered showers and isolated thunderstorms appear
possible at eastern terminals with VCSH remaining in the TAFS
after 17Z. Winds turn ESE at around 10kt in the afternoon. The
exception is again APF where light SE flow will shift westerly
around 10kt as sea breezes push inland. This will also bring VCTS
for the Gulf coast in the afternoon hours.

West Palm Beach 93 76 91 75 / 50 30 40 20
Fort Lauderdale 92 80 92 80 / 50 20 40 10
Miami 93 78 91 78 / 40 20 40 10
Naples 91 78 92 79 / 30 10 20 20




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