Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 200814
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
414 AM EDT Sun Aug 20 2017

.DISCUSSION...
Today-Tonight...A weak inverted low level trough will move slowly
across the south half of the peninsula and into the Gulf of Mexico.
A band of high moisture will overspread the area today as this
feature moves across, except in far northern sections where the
models indicate some residual drier air lingering.  This will set
up a rather large south to north POP gradient.  MOS shows 80 percent
along the south coast and 20 percent in the north but have settled
on 70 and 30%, which is not too different than the previous
forecast.

The HRRR model has been showing the main chances during the
afternoon, but southern sections should have some shower chances
in the morning.  The GFS indicates the high moisture keeping
POPs going overnight with highest values (50-60%) in the north.
Won`t go that high, but for now will carry chance POPs through the
night.

Clouds and precip will limit high temps across the south half today
with readings reaching the upper 80s there.  The far north interior
may still reach the mid 90s.

Mon...As inverted trough exits into the Gulf, pocket of drier air
works into CWA in its wake. Area of 1000-500mb mean RH of 35-40
percent and PW values sub 1.50 inches should reach SE areas early
in the day, advecting NW through remainder of forecast area by
late in the day. Will indicate isolated POPs south/central
counties and low-end scattered for the north, becoming dry across
the south part in the afternoon. Max temps a few degrees above
normal inland (near normal coast) with mins holding several
degrees above climo.

Tue...Global models consistent with next inverted trough
(tropical disturbance) approaching the SE FL coast Tue, about 24
hours earlier than previous guidance. Will trend POPs back upward
to good chance coverage (50 POP) Tue southern third, but isolated
showers/storms to dry across the northernmost CWA as moisture
advection will take a while to work up the peninsula. Lingering
convection into Tue evening over central/south counties, with
onshore moving showers/storms possible overnight from about the
Cape southward within moist SE flow.

Wed-Sat...Large pool of deep layer tropical moisture remains in
place across central FL mid week into the weekend as long fetch of
SE flow persists west of Atlantic anticyclone. By late in the
week, the flow may acquire a more S/SW component as high builds
southwest and weakening frontal trough drops into S GA and FL
panhandle. Series of weak surface low or perhaps a more
consolidated low may eventually form along the boundary and lift
NE over the Atlantic to our north. Pattern suggests high coverage
of showers/storms through the period with considerable cloudiness.
Greatest coverage of precip likely during the daytime, but with
chance of overnight showers and a few storms as well as flow
becomes S/SW. Max temps a few degrees above normal Wed, then near
normal Thu-Sat. Mins several degrees above climo through the
period.

&&

.AVIATION...
Mainly VFR this morning, thin high moisture will lead to a
generation of scattered showers/storms across the south half of the
area.  There may not be a distinct east coast sea breeze due to
considerable cloudiness and showers over the adjacent Atlantic, but
interior areas should have the main chance for storms.  KMLB-KSUA
are the most likely TAF sites to experience MVFR-IFR conditions with
the convection.  Some lingering mid level dry air could also produce
some quite gusty showers/storms.  It should take until after 18z for
isolated-scattered showers/storms to build up from the south towards
the interior sites.  The HRRR hasn`t been showing anything reaching
KDAB-KLEE this afternoon though.

&&

.MARINE...
Today-Tonight...Surface high pressure ridge axis will migrate north
of the waters while a weak inverted trough shifts across the
peninsula and into the Gulf of Mexico.  The models indicate a slight
tightening up of the pressure gradient as this occurs, especially
tonight when onshore winds become 10-15 knots across most of the
waters.  The onshore flow will tap into higher moisture values and
lead to scattered onshore moving showers and storms building
northward today and into tonight.

Mon...Long fetch of E-SE flow 10-15 knots, supporting seas of 2-3
ft nearshore and up to 4 ft offshore building to 5 ft offshore
Mon night. Low coverage of onshore moving showers and isolated
storms.

Tue-Thu...E-SE winds 10-15 kt becoming more southerly near 10 kt by
Wed and continuing Thu as surface high builds SW well offshore.
Seas generally 2-3 ft nearshore and up to 4 ft offshore. Scattered
to locally numerous showers and thunderstorms through much of the
period.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  90  77  88  76 /  30  40  40  10
MCO  91  76  93  77 /  40  30  30  10
MLB  88  79  89  80 /  60  40  20  10
VRB  87  77  90  76 /  70  30  20  20
LEE  94  77  94  77 /  30  20  40  10
SFB  92  77  93  76 /  30  30  40  10
ORL  91  77  94  77 /  40  30  30  10
FPR  87  77  90  77 /  70  30  20  30

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.

&&

$$

SHORT TERM/AVIATION...Lascody
LONG TERM....Spratt



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