Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 211843

Area Forecast Discussion
National Weather Service Melbourne FL
243 PM EDT Mon Aug 21 2017


Current-Tonight...Deep layer ridging north of ECFL is providing
deep, light onshore flow across the region. As drier air draws into
the area from the southeast the local HRRR model shows WDLY SCT
convection from near KMCO northward for the remainder of this
afternoon. Most areas will stay dry, however, as temperatures aloft
remain relatively warm. As PWAT values sink to between 1.30-1.50
inches across the coverage warning area into this evening, another
weak inverted tropical trough will approach from the southeast.
Increasing deep layer moisture will begin very late overnight across
the Treasure Coast with the potential for showers to return here
before sunrise Tue morning. Winds will fall light/variable to calm
tonight with lows generally in the 70s areawide.

Tue-Tue Night...Approaching inverted trough axis will move into the
southern peninsula. A fairly tight moisture gradient will develop
over the CWA; PWATs in excess of 2 inches southward and 1.30-1.50
inches northward. This, in turn, will create a likely tight PoP
gradient as well. Higher PoPs (50pct) over the deep south will taper
back to 20pct near/north of I-4. The resultant onshore, moist flow
will keep convection active Tue night with trough/moisture axis
along the Treasure Coast and adjacent coastal waters. May have to
watch for heavy rainfall potential along the immediate coast should
any banding set up here. Lower rain chances Tue night northward and
further into the interior. Highs will reach around 90 across the
south and 92-94 across the nrn interior.

...Previous Extended Forecast Discussion (slightly modified)...

Wednesday...Deep tropical moisture will remain across central and
south FL into the day on Wed with the low level easterly wave axis
across west central FL. This will spell low level S-SE flow on the
east side of the axis and very deep moisture with PWATS to 2.0 to
2.3 inches across the srn half of east central FL. Will have pops
from 50-60 percent across the south and generally 30-40 percent
across nrn sections. Locally heavy rainfall will be possible. Highs
around 90 south to mid 90s nrn interior.

Thursday...A deep southerly flow of air from the tropics and high
moisture levels with PWAT values to 2.0-2.3 inches will continue to
spell high rain chances into Thu. Will have pops in the chance to
likely range from 50-60 percent for southern areas with the risk for
locally heavy rainfall. 40 to 50 percent for northern areas. Will
see considerable cloudiness in the morning becoming mostly cloudy
into the afternoon. Highs upper 80s south to around 90/lower 90s

Fri-Sun...Exact forecast details into the weekend become less
certain with the evolution of a digging mid latitude trough along
the southeast Atlantic seaboard and the medium potential for
tropical development near FL early in the weekend per latest
Tropical Weather Outlook from NHC. ECMWF develops low pressure
associated with the mid latitude trough while GFS indicates
potential low pressure development near or east of the old tropical
wave that will linger near the area into late week. Both scenarios
show high moisture levels across the area with low pressure moving
away to the northeast through the latter part of the weekend. Main
concern at this point will be the potential for locally heavy rain
with scattered to numerous showers/storms Friday and Saturday before
rain chances lower to scattered range Sunday with lowering of deep
moisture across the area and developing low level onshore flow from
the northeast. Highs in the upper 80s to around 90 and lows in the
70s for the upcoming weekend.


.AVIATION...Primarily VFR. Drier air continues to build in from the
southeast with only a few showers/storms this afternoon mainly to
the west and north of I-4. Some model guidance is hinting at some
low clouds (around 1000-1500 ft AGL) in the overnight and early
morning on Tuesday but confidence is low.  Believe the best chance
for any MVFR ceilings will be from MLB-SUA as moisture begins to
increase in the overnight. Some showers will also be possible from
MLB-SUA during the overnight and early morning with a few
thunderstorms toward late morning.


.MARINE...Afternoon-Tonight...The surface high pressure ridge axis
will continue to promote an onshore wind flow. Wind speeds generally
around 10 kts, except 15 knots over the Gulf Stream south of
Sebastian Inlet. Seas will build 3-4 ft near shore and 4-5 ft well
offshore through the period. Drier deep layer air moving across the
waters this afternoon/evening will be replaced by increasing
moisture from the south late tonight as another inverted tropical
trough approaches. Scattered showers/isolated storms possible for
our southern zones after midnight and towards daybreak.

Tue-Tue Night...The easterly wave axis will move northwest into the
local coastal waters. Generally ERLY winds (ENE-ESE) 10-15 kts
during the day with winds veering more SE/S in the evening and
overnight depending on exact position of the trough axis. Seas 3-4
ft near shore and 4-5 ft offshore. An increasing threat for
showers/storms, especially Cape southward.

...Previous Extended Marine Forecast Discussion...

Wed...The easterly wave will move slowly west of the area with
southeast winds to 10-15 knots. Scattered to numerous showers and
storms and seas to 3-4 ft.

Thu-Fri...Southerly flow into late week expected with a higher than
normal coverage of showers/storms through the period with deep
tropical moisture lingering over the area. Seas generally 2-3 ft
near shore and 3-4 ft offshore.


DAB  75  91  75  93 /  10  20  10  20
MCO  74  95  76  96 /  10  20  10  20
MLB  79  92  78  91 /  10  30  20  50
VRB  77  91  75  91 /  20  40  30  60
LEE  76  95  78  96 /  10  20   0  20
SFB  75  95  77  96 /  10  20  10  20
ORL  75  95  78  96 /  10  20  10  20
FPR  79  91  75  90 /  20  40  30  60




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