Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 201507
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
1005 AM EST Mon Nov 20 2017

.UPDATE...

Clear and chilly start to Monday morning with L50s mins across all
but the barrier islands and far SE CWA. A well-defined land breeze
that developed along the immediate coast began to push inland just
after sunrise as synoptic flow veered to NE. Temps behind this
mesoscale "coastal front" have jumped a good 15+ degrees into the
L70s. Some open cell SC is also starting to advect onshore as the
warmer oceanic air begins to spread onshore. Morning RAOBs show the
extremely dry air in place with PWATs about 0.25" inland and 0.50"
along the immediate coast, where a strong subsidence cap exists just
above 900MB.

Remainder of today...shallow drainage flow inland will rapidly give
way to NE-ENE winds and warmer, ocean-modified air through late
morning. Expect a mix of sun/clouds as shallow open cell marine SC
develops beneath the strong subsidence cap. Maxes in the L-M70s
north and M-U70s south. Nosig changes to the inherited forecast.

&&

.AVIATION...VFR. SCT040 with CIGs near BKN035-040 along the southern
coastal corridor (FPR-SUA), developing farther north later tonight.

&&

.MARINE...Buoy/C-MAN obs show NE winds near 15KT across the north
and nearshore and 20KT south and well offshore. Winds/seas are not
yet supportive of an SCA for the central and southern near shore
legs. However, think seas will eventually build to SCA thresholds
(20KT/7ft) near the outer part of these legs by sunset or a little
thereafter, so there`s nothing at all to be gained by dropping back
to an SCEC, given the strong likelihood that SCA conditions will
commence within 8-12hr for those legs.

&&

UPDATE/AVIATION...Cristaldi
MID TERM...Combs
LONG TERM...Ulrich

&&

.PREV DISCUSSION... /issued 343 AM EST Mon Nov 20 2017/

Tonight...Low level easterly flow will become ESE/SE in the low
levels late with 850mbs winds turning to the south and setting up a
low level WAA pattern. This should induce prevalent cloudiness
development through the night and a chance of showers and slight
chance of lightning storms for the Treasure coast as moisture near
the old frontal boundary moves back northward. At the mid
levels...an advancing trough across the central Gulf will also
provide some mid level support late with PVA moving toward the area.
Lows will range from the upper 50s/lower 60s nrn interior to the
upper 60s along the Martin county coast.

Tue-Thu...An unsettled weather pattern will take shape across the
area through this time frame. Frontal boundary and deeper moisture
initially lifts back north across the area Tuesday, as an
approaching mid level S/W crosses the region. Cold temperatures
aloft and additional aid in lift from U/L jet north of the area will
support high coverage of showers, as well as a few storms, with PoPs
around 70 percent. Overall severe threat looks low at this time, but
isolated stronger storms are possible. As S/W lifts northeast,
moisture and rain chances decrease. However as frontal boundary
lingers across the central FL peninsula, sufficient moisture and
instability will remain for the development of scattered showers and
isolated storms. Rain chances then increase again into Thanksgiving
Day to around 60 percent, as a more energetic S/W trough develops a
weak low along the front across the eastern Gulf and shifts eastward
across Florida. This will again lead to scattered to numerous
showers across the region with the potential for a few stronger
storms.

Cloud cover will generally remain mostly cloudy with the quasi-
stationary boundary across the region and elevated rain chances.
However some breaks and peaks of sunshine should occur. Highs will
range from the mid to upper 70s for most locations Tue-Wed, and then
drop to the low to mid 70s Thu. Lows will be in the low to mid 60s,
except 50s/low 60s Thu night as front shifts farther south.

Fri-Sun...Differences still exist with the models late week in terms
of timing and exact path across Florida for weak low along the
front, as a secondary S/W trough axis shifts across the area.
Regardless moisture doesn`t quite clear the area, with current
forecast holding onto at least chance PoPs around 30-40 percent
across much of the area for Friday. Then as low shifts northeast
away from the area and front finally pushes south, a drier/cooler
northwest flow develops ending rain chances across the area for the
weekend. Temperatures remain near to slightly cooler than normal
through the period.

&&

.AVIATION...
Frontal cloudiness mainly south of KFPR should advance south and
east through the pre dawn hours. VFR conds expected today with a
redevelopment of some areas of marine stratocu moving onshore by
late afternoon. Will indicate BKN CIGs above 3000 ft tonight with
low level warm advection ensuing.

&&

.MARINE...
Today...N-NE winds through the pre-dawn hours will increase to 17-20
knots and then veer to the ENE/E into the afternoon. Will continue
SCA for all areas except Volusia near shore waters where an SCEC
will continue in effect. Seas will range from 4-6 ft Volusia coastal
waters to 6-7 ft offshore and in the gulf stream.

Tonight...Winds will veer to the east with pressure gradient
tightening some supporting winds to 17-22 knots. SCA continues most
of the waters with SCEC coastal Volusia expected. Some late night
convection may develop near the Treasure coast.

Tue-Fri...Frontal boundary lifts back north across the region
Tuesday leading to a more unsettled weather pattern and higher rain
chances that will continue through much of the week.

Breezy easterly flow will gradually decrease Tue afternoon, but
winds up to 15-20 knots with seas up to 6-7 feet will continue poor
to hazardous boating conditions. SCA has been extended for the Gulf
Stream waters through early Tuesday morning and then continue
offshore through the afternoon. Front will likely shift slightly
south into Wednesday with winds out of the northeast up to 10-15
knots and seas falling to 3-5 feet.

Low pressure is still forecast to develop over the eastern Gulf and
shift over the peninsula late this week. However, confidence in the
wind forecast remains lower than usual given the uncertainties in
the system`s strength and track. Seas 3-5 feet Thursday
deteriorating on Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  73  61  76  63 /  10  10  70  50
MCO  75  61  77  63 /   0  10  70  30
MLB  76  66  78  64 /  10  10  70  40
VRB  76  67  80  64 /  10  30  70  40
LEE  74  60  76  62 /   0  10  70  30
SFB  74  60  77  62 /  10  10  70  40
ORL  75  61  76  64 /   0  10  70  30
FPR  76  67  80  63 /  10  30  70  30

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 4 AM EST Tuesday for Volusia-Brevard
     County Line to Sebastian Inlet 0-20 nm.

     Small Craft Advisory until 4 PM EST Tuesday for Flagler Beach to
     Volusia-Brevard County Line 20-60 nm-Sebastian Inlet to
     Jupiter Inlet 20-60 nm-Volusia-Brevard County Line to
     Sebastian Inlet 20-60 nm.

     Small Craft Advisory until 10 AM EST Tuesday for Sebastian Inlet
     to Jupiter Inlet 0-20 nm.

&&

$$



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