Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 271305
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
905 AM EDT Tue Jun 27 2017

...High Coverage of Showers and Thunderstorms This Afternoon...
...Locally Heavy Rain, Gusty Winds and Frequent Lightning with
Stronger Storms Expected...

.UPDATE...
Morning central Florida soundings at Cape Canaveral AFS and Tampa
show similar moisture and instability profiles with PWATs around
1.93 inches and 500 mb temps hovering around -8 degs C. Sounding
data and 915 MHZ Cape wind profilers indicate SW/WSW flow through a
deep layer ahead of a frontal trough which will drop into central FL
this afternoon. Short range high resolution model guidance indicates
numerous showers and storms developing into the afternoon hours with
maximum coverage shifting slightly south from yesterdays convective
pattern as the frontal trough drops into the area. This should keep
the highest coverage across central sections including Orange,
Osceola, Brevard and Indian River counties. Mid level steering flow
is solidly from the southwest at 10-15 knots in the H7-H5 layer
which will allow deeper convection to move back toward the east
coast into the late afternoon and evening. Main concerns are
frequent lightning, gusty downburst winds to 40-50 mph and locally
heavy rainfall amounts in spots to two to four inches with the
strongest storms. Increased rain chances to 70 percent for all of
Brevard/Indian River, otherwise little change to ongoing forecast.

&&

.PREV DISCUSSION...
Today/Tonight...An encroaching surface boundary, elevated
moisture, and unstable conditions aloft will support another round
of numerous showers and thunderstorms this afternoon, with rain
chances increasing substantially along the Space and Treasure
Coast compared to recent days.

Immediate concerns are focused on the potential for reduced
visibility in the vicinity of the Tucker Wildfire located south of
State Road 520 and just to the west of Interstate 95 near
Rockledge. Veering winds from their current south-to-north
orientation to southwest by sunrise could allow dense smoke to
settle between MM196-201 and lead to temporary road closures.
Travelers headed through this area are urged to check traffic
conditions before starting their commute.

Early morning satellite and observational analysis indicates a
weak surface boundary located just to our north this morning. The
atmosphere remains moisture-loaded along and ahead of the front,
with precipitable water near 2.00" areawide. While multi-layer
clouds this morning will delay surface heating, convective
temperatures will still be easily met and exceeded by late
morning and early afternoon. Initial convection (as early as
11AM-NOON) will be in association with the sea breeze and
differential heating boundaries, with subsequent boundary
interactions increasing coverage through the remainder of the
afternoon. Cooler temperatures aloft, down to -8.0 to -8.5C at
500 mb, will help sustain more vigorous updrafts and could aid in
the development of strong storms: frequent lightning and brief
gusty winds being the primary threats. Storm motion is still
expected to be erratic and more a result of boundary interactions
and propagation, though slightly elevated steering flow out of
the southwest will push some of the storms back to the coast.
Localized flooding from quick and excessive rainfall remains a
possibility in any slow-moving storm that develops today.

Will carry a mention of scattered showers and isolated storms
through the midnight hour, but given the expected earlier start
to convective initiation, suspect things will quiet down
earlier then that. Seasonable temps forecast with highs a degree
or two either side of 90, overnight lows in the mid 70s.

Wed-Thu...The forecast for this period undergoes little change as
the main features should move about as previously assessed. The
period forecast begins with the weakening frontal trough and
associated banded moisture sagging into Central Florida as the
center of an expansive high pressure moves toward the Mid-Atlantic
states on Wed from the continental interior. Local wind flow around
the south-side will otherwise neglect the eroding boundary to setup
an easterly onshore pattern. Yet, increased available moisture will
offer plenty of fuel for showers and storms favoring an inland skew.
By Thu, the high pressure center will have moved offshore the
Carolinas allowing local winds to shift ESE. Convective distribution
will be similar to Wed except better chances inland and northward
thru the ECFL forecast area. Storms will be capable of dumping
locally heavy rain totaling a couple of inches in spots each day.
Max Temps in the U80s/L90s with Min Temps in the L/M70s, but with
some U70s along the immediate coast.

Fri-Mon...The forecast across the 4th of July weekend will see
gathering moisture over the northern Gulf of Mexico spreading ENE
into Old Dixie Fri-Sat. Concentrations across N Florida
Panhandle/Peninsula further aided by local SE wind flow around the
Atlantic ridge. The associated axis tries to reassert while the
eroding trough becomes hard to find by Sat. Building high pressure
aloft will also allow local circulations to rudder. Hence convective
distribution will continue to favor inland locations aided by
embedded sea breezes, although coastal locations will not be void,
especially from Titusville to Daytona. Rain chances slightly above
normal for most places, except near normal for Treasure Coast.
Planned fireworks festivities intermingled with displays of
lightning from lingering storms into the evening hours. Max Temps in
the U80s/L90s with Min Temps M/U70s.

&&

.AVIATION...
VFR through late morning with increasing chances for MVFR/IFR
visby and MVFR cig reductions in SHRA/TSRA this afternoon. Early
onset (16Z- 18Z) expected along the east coast, starting no more
than a couple hours later across the interior aerodromes. Have
advertised this with tempo groups at all locations. Users should
monitor for timing adjustments as we watch trends in convective
development through the day.

&&

.MARINE...

Update...Little change to winds/seas for late morning update. Expect
scattered to numerous storms near the east coast later this
afternoon with potential for stronger storms producing wind gusts
greater than 34 knots, locally heavy rain and dangerous lightning.

Previous...

Today/Tonight...An encroaching surface boundary will allow for
greater coverage of afternoon showers and thunderstorms along the
entire coast of east central Florida. Winds will start off from the
south to southwest this morning and turn onshore along the coast as
the sea breeze develops this afternoon. Despite the expected wind
shifts, speeds should remain at or below 10 knots outside of gusty
winds from thunderstorm activity.

Wed-Sat...A weak frontal trough will slowly sag south toward the
Central Florida waters by Wed as it gradually dampens and erodes.
Associated moisture will prompt rain chances to be higher than
normal through mid-week. By Thu, a large area of high pressure will
transition off the Mid-Atlantic Seaboard causing local wind flow to
become prevailing from the east and onshore. By Fri, local winds
turn SE as the high pressure transitions farther seaward off the Mid-
Atlantic Coast. The ridge axis should fully re-establish for Sat
locating just north of Central Florida waters and bolstering the
prevailing SE flow. Surface winds expected to remain at or below 10
knots outside of thunderstorm activity with seas generally 2 feet
Wed. Then, building onshore wind flow of 10 to 15 kts will support
seas 2-3 feet late week into the weekend.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  91  74  87  74 /  70  30  40  20
MCO  93  73  92  74 /  70  40  60  20
MLB  92  74  89  75 /  70  50  50  20
VRB  92  73  90  74 /  70  50  50  30
LEE  92  73  91  76 /  70  30  60  20
SFB  90  73  91  74 /  70  40  50  20
ORL  92  73  91  75 /  70  40  60  20
FPR  91  73  90  73 /  60  40  50  30

&&

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

$$

Volkmer/Johnson



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