Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 090822
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
422 AM EDT Thu Aug 9 2018

.DISCUSSION...

Today-Tonight...Axis of Atlantic high pressure ridge will remain
over south Florida.  Surface to 700 mb flow will be out of the west
and the gradient wind does not look strong enough to prohibit an
east coast sea breeze.  The GFS shows precipitable water close to
average around 1.7 inches, except a few tenths higher in the south.
The latest GOES precipitable water produce seems to support this,
but skies are rather clear with no showers over the surrounding
waters, so there is some subsidence occurring.

A mid-upper level low over the southeast Gulf of Mexico is not
moving much and with its proximity, 500mb temps will be minus 7
to 8C. MOS PoPs are quite low, 10% inland and 20-30% along the
coast. With plenty of daytime heating, high temps will reach the
lower-mid 90s and despite some drier air aloft, the instability
and moisture look sufficient for scattered PoPs areawide. The
highest chances will be along the coast, especially in the south
where we have PoPs 40-50%.

The presence of the drier mid level air will keep the gust
potential elevated, and a few strong storms should be capable of
producing gusts near 50 mph.

MOS PoPs continue low this evening, but will keep a small chance
for showers/storms in case boundary interactions continue past
sunset like last evening.

Fri-Sat...
Latest RAP40 analysis of the H30-H20 lyr shows a 70-90KT jet streak
extending from the NW corner of BC, arcing acrs nrn Canada, and
digging into the Great Lakes region...secondary 60-80KT jet streak
lifting out of the OH river valley into New England. These two WX
features will interact to maintain a broad troffing pattern over the
eastern seaboard thru week`s end that will keep the axis of the
Bermuda Ridge suppressed south of Lake-O and the Nrn Bahamas. This
in turn will generate a westerly flow thru the H100-H70 lyr acrs the
region, a flow pattern that will concentrate diurnal precip over the
east central peninsula.

Currently, the Bermuda ridge is broken into two parts, one closed
H100-H70 anticyclone extending from the MS/AL bootheels acrs the
Bahama Bank, and the wrn flank of the primary ridge positioned well
SE of Bermuda. Troffing over the ern seaboard will amplify a bit
into the weekend as the nrn jet streak digs into the NE CONUS,
forcing the closed anticyclone to retrograde into the GOMex on Fri
where it will slowly weaken. This will generate a W/NW flow pattern
that climatologically is not all that favorable for diurnal precip.
Furthermore, GFS fcst PWat values arnd 1.75", H100-H75 mean RH
values btwn 60-70pct, and H85-H50 dewpoint depressions btwn 7-10C
will hamper precip formation...while H70 temps arnd 9C and H50 temps
arnd -7C will yield meager lapse rates btwn 5.5-6.0C/KM. Will go
with 30pct interior, 40pct coastal, with abv avg temps...L/M90s for
aftn maxes, L/M70s for overnight mins.

The wrn flank of the primary Bermuda ridge will rebuild into the nrn
by Sat Bahamas in the wake of the retrograding anticyclone, though
continued troffing along the ern seaboard will keep its axis
suppressed over south FL. H100-H70 winds will back to the W/SW,
allowing low/mid lvl moisture to recover slightly with fcst PWats
increasing to 1.75"-2.00". Wrly flow thru H100-H70 will continue to
favor the east central Peninsula for diurnal precip, PoPs increasing
to 40pct interior and 50pct along the coast. Continued warm due to
the wrly flow...aftn maxes in the L/M90s...overnight mins in the
L/M70s.

Sun-Wed...
Troffing pattern will persist east of the MS River Valley into early
next week before gradually dampening out into mid week. This will
allow the Bermuda Ridge axis to slowly build into central FL, with
the H100-H70 mean flow gradually backing from SW on Sun to due S by
daybreak Wed. The increasing southerly component will tap sufficient
tropical moisture to push PoPs into the 50-60pct range Sun/Mon. A
new slug of dry air is fcst to advect into FL by midweek. PoPs will
continue to favor the east coast thru Tue, but dropping back to 30-
40pct, then 30pct areawide on Wed as low/mid lvl flow orients itself
to S/SE, parallel to the central FL Peninsula. No sig change in PoPs
as the prevailing srly wind component keeps them AOA climo...maxes
L/M90s, mins L/M70s.

&&

.AVIATION...VFR this morning then isolated to scattered storms are
expected to move west to east across the peninsula this afternoon and
early evening. The greatest chance should be at coastal terminals
where the east coast sea breeze will increase boundary interactions,
so have included vicinity thunder there. Probabilities still look
too low to include mention of vicinity thunder at interior terminals
though. Convection should push offshore a little after sunset with
conditions VFR late tonight.

&&

.MARINE...
Today-Tonight....High pressure ridge axis south of the waters will
produce a westerly wind 10 knots or less, except for a diurnal
increase tonight to 10-15 knots offshore.  Seas 1-2 feet near shore
and 2-3 feet well offshore.  Steering level flow out of the west
looks a little more pronounced today so mariners can expect isolated
to scattered storms moving offshore during the afternoon and evening.
There`s a chance for wind gusts 34 knots or greater with isolated
strong storms.

Fri-Mon...Broad troffing pattern over the ern seaboard will keep the
Bermuda ridge axis in the vcnty of Lake-O and the nrn Bahamas into
early next week. Light to gentle SWrly breeze will prevail, backing
to S/SE in the early aftn/late evng hrs due to the sea breeze
circulation. Seas AOB 2FT nearshore and 2-3FT offshore on Fri,
subsiding to AOB 2FT areawide Fri night thru Mon. Primary marine
threat will be sct tsras moving offshore each aftn.

&&

.HYDROLOGY...
The Saint Johns River at Astor is forecast to remain nearly steady,
close to flood stage through late week.  A River Flood Warning
remains in effect there until a slow decline commences late this
weekend or early next week. Elsewhere, river levels are forecast
to remain within Action Stage over the next 5 days.

Please refer to our River Flood Warnings/Statements (FLSMLB) and
Hydrologic Statements (RVSMLB) for the most recent stage and
forecast information.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  94  75  91  75 /  30  20  40  20
MCO  95  76  92  76 /  30  10  30  20
MLB  93  75  91  75 /  30  20  40  20
VRB  93  73  90  74 /  40  20  40  20
LEE  94  77  92  76 /  30  10  30  20
SFB  95  77  93  76 /  30  20  30  20
ORL  95  77  93  76 /  30  10  30  20
FPR  92  73  90  74 /  40  20  40  20

&&

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

$$

SHORT TERM...Lascody
LONG TERM....Bragaw



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