Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 200739
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
339 AM EDT Thu Jul 20 2017

.DISCUSSION...
A weak surface pressure pattern will remain in place today while
in the mid and upper levels a cutoff low is forecast to begin
retrograding from the Carolinas toward north Florida. This will
keep the Atlantic ridge suppressed over the Bahamas and Florida
Straits and maintain light west to southwest flow through the
column. When combined with anomalously high moisture, another
round of scattered to numerous lightning storms is expected to
take shape this afternoon. While storm initiation and evolution
are never exactly the same for two or three days in a row, there
are some similarities to yesterday that would suggest better rain
chances across our central and southern zones.

Initial development of showers and storms over our forecast area
will take place after noon along the inland-moving sea breeze,
especially over the Space and Treasure Coasts. Activity will
shift west as the (pseudo) sea breeze pushes inland along with
convective outflows. More rigorous boundary collisions over the
interior should generate a few strong storms, with brief wind
gusts to 50 mph, very heavy rainfall, and frequent to excessive
lightning the primary threats. With the approach of the cutoff
low, mid-level temps are forecast to cool to -7 to -8C, suggesting
a potential for small hail especially across northern and central
sections.

MOS guidance indicates the lowest PoPs along the Volusia Coast
(30-40%), steadily increasing (up to 60-70%) to the south and
west. This is also supported by both the HRRR and local WRF that
show the best coverage from the Orlando metro area to Lake
Okeechobee eastward to the coast. Despite the expected lower
coverage across the north, will still need to watch for stronger
storms given the cooling temps aloft.

Expect most of the available energy to be consumed by sunset with
only debris rain dissipating by midnight.

Fri...Flow regime ascd with Bermuda High across the Bahamas to S FL
will continue to favor development of afternoon storms over the ECFL
area. PWAT value around 2 inches with light to modest SW flow from
the sfc through steering level will favor the E coast and adjacent
Atlantic waters for activity well into evening. Max temperatures
will range from the upper 80s to low 90s with lows in the M-U70s.
Precip coverage wl range from 50 to 60 percent.

Sat-Wed...The Bermuda Ridge is shown shifting back to the N during
the weekend and remaining in place well into next week over the
forecast area as it stretches WWD across most of the Gulf of Mex. An
east coast trough stretching NWD along the Mid Atlc coast wl keep
upstream conditions somewhat unsettled through at least the middle
of next week. Seasonal moisture values with PWAT 1.6 to 1.8" and
numerous afternoon boundary interactions justify a typical range of
sct pcpn chcs in the forecast each aftn. Seasonal temps in the M70s
with highs in the L90s are expected.


&&

.AVIATION...
Moisture remains high enough to support another round of SHRA/TSRA
this afternoon. Initial development is expected along the sea
breeze, with activity spreading inland through the afternoon.
With that said, 2-3 hour TEMPO groups were introduced with the 06Z
forecast package, between 17Z-20Z along the coast from KTIX-KSUA,
and 20-23Z for our inland aerodromes. Opted to keep VCTS at DAB
for now as slightly drier air should lead to lesser coverage
there.


&&

.MARINE...
Today/Tonight...The Atlantic subtropical high will remain centered
to our south and east, keeping winds light out of the south.
Expect onshore component to develop during the afternoon as the
sea breeze pushes inland. Seas 1-2 feet, occasionally 3 feet well
offshore.

Another round of lightning storms forecast to develop close to
the intracoastal waters, especially along the Space and Treasure
Coasts. Mariners are reminded that sudden wind shifts can occur
well ahead of the heaviest rain of a thunderstorm.

Fri-Tue...Ridge axis proximate to the waters during the forecast
period will allow for generally favorable boating conditions with
seas averaging around 1-2 ft within 20 NM and around 2-3 ft
farther offshore. Predominant S/SE flow into late Fri will light
to gentle S/SW into the weekend and early next week. An onshore
wind will develop along the immediate cst each afternoon with the
sea breeze.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  90  75  91  74 /  40  20  50  30
MCO  92  75  95  75 /  60  30  60  30
MLB  91  75  91  74 /  60  30  50  30
VRB  91  75  91  74 /  60  30  50  30
LEE  92  75  96  77 /  60  30  60  20
SFB  91  75  96  76 /  60  30  50  30
ORL  92  75  96  76 /  60  30  60  30
FPR  91  75  90  73 /  60  30  50  30

&&

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

$$

Ulrich/Pendergrast


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