Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 200858

Area Forecast Discussion
National Weather Service Melbourne FL
458 AM EDT Sun May 20 2018


Current...Increasing south flow in the low to mid levels continues
to draw a significant plume of moisture up the peninsula this
morning. Numerous showers over the southern peninsula, aided by
coastal convergence and favorable lift aloft will spread across the
Treasure Coast and as far north as Cape Canaveral early this
morning. Potential for heavy rain and even some lightning will exist
along the Treasure Coast, with lighter activity across inland areas
like Okeechobee and Osceola counties.

Today/Tonight...Plenty of ingredients are in place for another wet
day, with the greatest chances for precipitation transitioning from
the coast this morning to inland areas this afternoon. South to
southeast flow continues to draw an abnormally moist airmass overtop
the peninsula as we remain sandwiched between a weak trough over the
eastern Gulf of Mexico and high pressure over the western Atlantic.
Though surface heating will be minimal given the opaque cloud cover,
coastal convergence and embedded pieces of energy rounding the
mid/upper level trough should spark several rounds of showers with
embedded isolated thunderstorms. PoPs were kept high (60-70%)
areawide; however, feel that the best rain chances will transition
from the nearshore Atlantic waters and adjacent coastal areas this
morning to inland areas this afternoon as some dry air advects in
from the southeast. Repeated bouts of heavy rainfall with
accompanying localized flooding pose the greatest weather threat
today, though storms will also be capable of producing wind gusts
between 30 to 40 mph and lightning. Max temperatures forecast within
a degree or two of 80 (below normal for mid May) to account for
expected cloudy skies and rain.

There is some uncertainty with respect to how much drying will
advect in from the southeast later today. Regardless, most models
indicate a renewed push of deep moisture advecting northward
overnight. This should transition the highest chances for
precipitation back to the coast, especially south of Cape Canaveral.
Overnight mins a couple of degrees above climo, particularly along
the coast given the mild onshore flow.

Mon-Sat...The Atlantic ridge axis will remain the dominant weather
feature with a moist south to southeast flow keeping rain chances
above normal (50 to 60 percent) most days supporting mainly
daytime showers and storms. The ridge axis is forecast to
gradually shift southward and weaken during mid to late week as a
trough develops over the Southeast US. A slight reduction in the
deep moisture by Wed will allow rain chances to decrease to 30-40
percent for most areas. It will remain humid with max temps in
the mid 80s.

Both GFS and ECMWF show a mid level trough developing over the
Gulf of Mexico late in the week. The GFS retrogrades a piece of
energy SW from the base of a departing shortwave trough off the US
east coast. The real difference is how each model handles lower
pressure at the surface. The ECMWF continues to show low pressure
developing directly underneath the upper low over the central Gulf
on Fri. This looks suspect as the best support for sfc low
pressure would be to the ascending (east) side of the upper low,
closer to the GFS solution. But both models show deep tropical
moisture overspreading the FL peninsula during the first part of
the upcoming holiday weekend which will prompt high rain chances
with a threat for heavy rain and localized flooding due to already
wet conditions.


.AVIATION...Highest rain chances along coastal terminals through
early afternoon before activity develops and spreads inland this
afternoon. Widespread MVFR VSBYs likely in rain with spotty IFR
tough to time. Ceilings VFR to occasional MVFR in showers and
isolated storms.


Today/Tonight...Synoptic pattern supports 10-15 knots of east to
southeast flow this morning, however, widespread showers and
isolated thunderstorms are disturbing the wind flow. Expect
generally southeast winds to develop this afternoon as best chance
for showers transitions inland. Winds 10-15 knots nearshore and 15-
20 knots nearshore will keep seas choppy: 3-4 near the coast, up to
6 feet well offshore.

Monday-Thursday...The axis of the Atlantic high pressure ridge will
stay north of the waters into Wed. The models show this will
continue to produce a breezy southeast wind flow and rather
agitated seas at least through Tue. By Thu, the ridge axis is
forecast to settle into the waters, which should knock winds down
closer to 10 knots. Moisture is forecast to decrease a bit during
mid week, as early as Tue, so periods of showers with isolated
storms should become less frequent.


DAB  80  73  82  69 /  70  40  60  30
MCO  79  71  84  71 /  70  40  60  20
MLB  81  74  83  72 /  70  40  60  30
VRB  81  73  83  71 /  70  50  60  30
LEE  80  71  84  70 /  70  50  60  20
SFB  79  71  84  69 /  70  40  60  20
ORL  79  71  84  70 /  70  40  60  20
FPR  81  73  83  71 /  70  50  60  30





LONG TERM....Kelly
AVIATION...Ulrich is the U.S. government's official web portal to all federal, state and local government web resources and services.