Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 210021

Area Forecast Discussion
National Weather Service Miami FL
721 PM EST Fri Jan 20 2017

There will be VFR conditions tonight with light winds. Patchy fog
may develop over the interior, but should say clear of the TAF
sites. Aft 21/1500Z, southerly winds will increase to between
11-14 KT, then dwindle during the evening. Dry conditions and
partly cloudy skies will prevail through the period.


.PREV DISCUSSION... /issued 341 PM EST Fri Jan 20 2017/



High pressure over South Florida will weaken tonight into
Saturday, as a strong mid to upper level trough shifts eastward
from the Western United States into the Central United States.
This will allow for a south to southwest steering flow over South
Florida tonight into Saturday allowing for some low level moisture
to work into the area. However, the mid to upper levels of the
atmosphere will remain dry through this time keeping the weather
dry across South Florida. Fog formation is also possible late
tonight into early Saturday morning across South Florida with the
best coverage over the interior and west coast metro areas due to
the increasing low level moisture.

The strong mid to upper level trough will continue to move east
from the Central United States into the eastern United States. Low
pressure will also be developing over the Southern Gulf Coast
States on Sunday before moving northeast into the southeast
Sunday night and into the Mid Atlantic States on Monday. This low
will also allow for a pre-frontal trough to develop over the
eastern Gulf waters on Sunday morning before moving across the
Florida Peninsula late Sunday afternoon into Sunday evening. A
cold front associated with the low will also develop over the
central Gulf waters on Sunday and move east through the Florida
Peninsula late Sunday night.

Ahead of the pre-frontal trough, the winds will be breezy from the
south allowing for deep tropical moisture to overspread the area,
before veering to more southwest Sunday night ahead of the cold
front. At this time, it looks like there will be two rounds of
showers and thunderstorms. The first will be with the passage of
the pre-frontal trough late Sunday afternoon into Sunday evening,
and the other round will be with the passage of the cold front
late Sunday night into the pre-dawn hours Monday morning.

There will also be a mid to upper level jet around 100 knots with
a low level jet up to 50 knots developing in the Gulf of Mexico
on Sunday which should move east across the Florida Peninsula
Sunday night. The 500 mb temps will also be cooling down from -9C
Sunday evening to -12 late Sunday night over South Florida with
the passage of the strong mid to upper level trough. This will
allow for some of the storms late Sunday afternoon through Sunday
evening to become strong to severe over South Florida.

The first round of storms will be capable of producing gusty
winds, hail, and even a few tornadoes, while the second round of
storms will be primarily a gusty wind threat as winds are more
unidirectional with height, though isolated embedded tornadoes
will also be possible.

Residents and visitors to South Florida should monitor the latest
forecasts from our office on this developing severe weather
threat for late this weekend.

The winds will be southerly tonight into Saturday night before
swinging southwest for Sunday and Sunday night. The speeds will be
10 knots or less tonight before increasing to breezy conditions by
Saturday night and to windy conditions on Sunday and Sunday night.
Frequent gusts to gale force will be possible Sunday night over
all South Florida waters. The seas will increase to over 7 feet
late Sunday and potentially over 15 feet open Gulf waters by
Monday morning.

If these trends continue for South Florida waters in later
forecast, then a Small Craft Advisory or Gale Watch may be
issued sometime Saturday for the Sunday-Monday period.

The cold front should be south and east of South Florida by midday
Monday allowing for high pressure to build into the area from
the north. The high will remain over the Florida Peninsula for
most of next week leading to mostly dry weather over South Florida.

The threat of rip currents will remain low tonight into Saturday
along both the east and west coast beaches of South Florida. The
risk will then increase late this weekend into early next week,
particularly along the Gulf Coast with strong onshore winds.

With strong onshore winds expected Sunday night into early Monday,
there will be a risk of coastal erosion and minor coastal
flooding of particularly vulnerable areas along the Gulf Coast of
South Florida. The magnitude of the risk will depend on the
timing of the strongest winds and whether this coincides with the
time of high tide.


West Palm Beach  63  83  68  85 /   0  10  10  30
Fort Lauderdale  68  82  71  82 /   0   0  10  20
Miami            68  83  70  84 /   0   0  10  20
Naples           65  81  68  80 /  10   0  10  50



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