Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 181726 AAC
AFDMFL

Area Forecast Discussion...UPDATED
National Weather Service Miami FL
1226 PM EST Mon Dec 18 2017

.AVIATION...
The winds will remain easterly at 5 to 10 knots this afternoon
before decreasing to light and variable conditions tonight at the
east coast taf sites. KAPF taf site winds will be westerly this
afternoon at 5 to 10 knots, as the west coast sea breeze develops
and pushes inland. The winds will then decrease to light and
variable conditions tonight at KAPF taf site. The weather will
remain dry along with VFR conditions this afternoon into tonight,
but could fall down into MVFR conditions at KAPF and KTMB taf
sites late tonight if any fog develops over these taf sites.

&&
AVIATION...54/BNB


.PREV DISCUSSION... /issued 910 AM EST Mon Dec 18 2017/

UPDATE...
Most of the fog has burned off this morning over South Florida,
except over portions of Collier County. The fog should continue to
burn off over through the late morning hours in Collier County and
be gone by noon time. The weather will also remain dry over all of
South Florida for today, as high pressure remains over the
Southeastern United States. This will keep an easterly wind flow
over South Florida leading to a moderate risk of Rip Currents for
the east coast beaches. Therefore, the only change to the forecast
is to remove the fog wording from the zones for this morning,
except for Collier County.

&&
UPDATED...54/BNB


PREV DISCUSSION... /issued 637 AM EST Mon Dec 18 2017/

AVIATION...
The winds will be light and variable early this morning before
increasing from the easterly direction around 10 knots late this
morning into the afternoon hours over the east coast taf sites.
KAPF taf site will also see light and variable winds this morning
before going westerly this afternoon, as the west coast sea breeze
develops and pushes inland. The weather will remain dry today into
tonight over all of the taf sites along with VFR conditions in the
ceiling and vis. The only exception to this is early this morning,
where some fog will lower the vis and ceiling down into MVFR
conditions until 13Z at mainly KTMB, KOPF, and KAPF taf sites.

&&
AVIATION...54/BNB


PREV DISCUSSION... /issued 249 AM EST Mon Dec 18 2017/

DISCUSSION...
High pressure continues to dominate the pattern through the
weekend. The surface high, which was to our north, is building to
the southeast. There is also a strong 500mb ridge at 590+ dm over
the region. This has kept the area mostly dry. However, a weak
convergence line has developed over the Atlantic waters, allowing
a weak line of showers to develop. The HRRR does show this
transitioning to the north over the next few hours. it also show a
few isolated showers/sprinkles along the Atlantic coastal areas.
Any showers should be brief with little accumulation.

In the interior, especially west of the lake, fog has developed
this morning, despite the high clouds. This is probably due to the
cooler temps already in place, as well as dew points around 60, as
well as the wind decoupling and dropping to zero mph. The HRRR
indicated it may remain around until after sunrise, and possibly
around 15z. A Dense Fog Advisory has been issued for Interior
Collier County, as well as Glades and Hendry Counties tonight.
There is a small chance the fog may also develop over interior
Palm Beach County as well, but there are no reports, and cloud
cover is hampering satellite analysis attm. Fog may also occur
tomorrow night in similar areas. By the end of the week, the flow
turns more southwesterly, which has the potential to lead to more
widespread fog formation, if conditions are right.

The dry, warm pattern looks tom continue through the weekend, with
possible isolated sprinkle periodically, mainly along the coast
and in the Lake region. however, the chances are too low to
mention in the forecast, other than a slight chance early Sunday
morning. Temperatures are forecast to be on the warm side through
the weekend, with highs in the 80`s and lows in the 60`s to around
70.

Over the weekend, the GFS shows a strong 500 mb trough digs over
the high plains, and a surface low moves over the great lakes.
This low will drag a cold front into the southern US Friday night
into Saturday. The front will begin to stall across North Florida
as the low pulls quickly to the north northeast. This still
remains far enough away to keep South Florida with a dry forecast
this weekend. However, by the beginning of the week, a surface low
is progged to develop along the boundary, off the Carolina coast.
This would slowly push the boundary to the southeast. The upper
level trough persists through this time frame, and slowly moves
eastward, with a negative tilt, for the beginning of next week.
This will bring instability to the region for the beginning of the
week, however, models are not giving any significant chance for
rain with the frontal passage. The GFS does show that some showers
may be possible over the Atlantic waters.

Also, looking at the ECMWF, it is not as progressive with the
500mb trough, keeping it much further west, and the cold front
well to the north of the region. Given this uncertainty, and lack
of consensus, as well as GFS showing mostly dry passage, have kept
PoPs mostly below 15%, except for a slight chance Sunday morning
along the Atlantic coast of Palm Beach and northern Broward
Counties.

MARINE...
High pressure will keep mostly dry conditions across the region
under an easterly flow. An isolated shower/sprinkle cant be
totally ruled out, but more the exception then a rule. Seas are
forecast to be generally 1 to 3 feet in the Atlantic, although
seas east of Key Largo may increase to around 4 feet at times. For
the Atlantic waters, the wind is forecast to be easterly today
through Wednesday morning across the Atlantic waters at around 8
to 12 kts, with period increase to around 15 kts off the southern
Miami Dade coast. The wind is then forecast to become more
southerly to southwesterly for the latter half of the week. There
remains a moderate risk of rip currents for most of the South
Florida Atlantic beaches for today and tomorrow.

For the Gulf waters, the wind looks to be more variable today,
becoming easterly up to 10 kts tomorrow, then follows a similar
trend as the Atlantic waters. There is a minimal risk of rip
currents for the Gulf beaches.

AVIATION...
Light and variable winds will prevail for the TAF sites through
the remainder of the night with VCFG possible in the interior.
Dry conditions are expected, with the exception of a few showers
east of KPBI. Bases of the few/sct low clouds tonight will
continue layered from 3500 to 5500 FT agl. East southeast winds
are forecast to increase to near 10 KT across the peninsula aft
18/1500Z, then diminish this evening.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  81  68  80  68 /  10  10   0  10
Fort Lauderdale  81  71  81  70 /  10  10   0  10
Miami            82  70  82  69 /  10  10   0  10
Naples           83  67  84  65 /  10   0   0   0

&&

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

UPDATE...54/BNB
DISCUSSION...13
MARINE...13
AVIATION...54/BNB







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