Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 210754

Area Forecast Discussion
National Weather Service Melbourne FL
354 AM EDT Mon Aug 21 2017


Today...Mid level inverted trough over the central Gulf will pull
farther away and allow a ridge to build in over the area.  This will
pull a band of high moisture away and drier air will work in from
the east and replace it. GOES 16 already confirms this drier air
was crossing the northern Bahamas and our southern waters. This
drying will be substantial enough to preclude any daytime POPs
across the south half of the area as precipitable water is
forecast to fall to around 1.3 inches.

The GFS generates some precip this morning from about Orlando and
Cape Canaveral northward and MOS has isolated to scattered rain
chances. There is a small pocket of Atlantic showers working north
along the coast early this morning, but the model appears to be
overdoing precip generation. Only plan to carry a small shower
chance in the north half this morning, then have a slight thunder
mention this afternoon right around the Ocala National Forest.
Will also need a small coastal POP along the coast of Indian River
and Brevard county prior to sunrise.

Tonight...Deep layer high pressure ridge to our north will provide
deep easterly flow.  Drier air over the area will preclude POPs
except in the south where moisture will start to return as the next
inverted trough approaches.  With the amount of drier air preceding
this feature, won`t go above MOS POPs as the models charged moisture
back into the area a little too quickly with this last inverted
trough.  MOS has 20-30% POPs along the Treasure Coast after
midnight, and have followed close to that.

Tuesday...Low level tropical wave axis is forecast to reach the
Treasure coast during the morning hours and extend NE across the
Atlantic. A very dry airmass is forecast initially northwest of the
low level easterly wave axis during the morning with PWATs around
1.2 inches from Daytona/Orlando and Kissimmee northwestward as deep
moisture moves onshore across the Treasure coast with PWATs to 2.2
inches. Will forecast highest rain chances across srn sections to 50-
60 percent and have lower pops in the 20-30 percent range across nrn
areas with GFS hanging on to dry airmass here into the afternoon.
Expect scattered showers and isolated storms to move onshore from
the Atlantic through the day with the risk for locally heavy
rainfall mainly confined to srn sections. Highs will reach around 90
across the south and 92-94 across the nrn interior.

Tuesday night...The low level tropical wave is forecast to sharpen
near the east coast with a higher coverage of showers and isolated
storms east of the wave axis from around the Cape to along the
Treasure coast through the overnight hours (to 40-50 percent). Lower
rain chances are expected inland to around 20 percent from Osceola
northward with lingering convective chances across Okeechobee county
through the night.

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 2.2 to
2.4 inches across the srn half of east central FL. Will have pops
from 60-70 percent across the south and generally 50-60 percent
across nrn sections. Locally heavy rainfall will be possible. Highs
around 90 south to lower 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 likely range
from 60-70 percent with the risk for locally heavy rainfall. 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...Mainly VFR. Local MVFR in onshore moving showers about
KFPR-KMLB prior to sunrise.  Also, expect a small chance for showers
this morning and into afternoon from about KDAB-KSFB-KLEE.


Today-Tonight...High pressure ridge axis north of the waters will
provide an onshore wind flow with speeds around 10 knots in the
north and 15 knots in the south.  This will gradually build seas,
reaching 4-5 feet offshore tonight.  An approaching inverted trough
late tonight will increase marine showers south of Sebastian Inlet.

Tue...E/SE winds to 10-15 knots with easterly wave axis across
the waters. Seas will reach 3-4 ft near shore and 4-5 ft offshore
with a high coverage of showers and storms mainly south of Cape

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  89  77  90  76 /  20  10  20  20
MCO  92  76  93  76 /  20  10  30  20
MLB  90  80  90  78 /  10  10  40  40
VRB  90  78  89  75 /  10  20  50  50
LEE  93  77  94  77 /  20  10  20  20
SFB  92  76  93  77 /  20  10  20  20
ORL  92  76  93  77 /  20  10  30  20
FPR  89  78  89  75 /  10  20  50  50




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