Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 191942
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
342 PM EDT Tue Sep 19 2017

.DISCUSSION...

Tonight...The GFS shows a weak surface trough oriented southwest to
northeast lingering along/offshore the Treasure Coast.  Moisture
will remain elevated near this trough so PoPs will remain necessary
from south Brevard to Okeechobee and the Treasure Coast overnight.
With weak large scale convergence from this feature, will have to
watch for locally heavy rain along the coast again. The GFS picks
out the Treasure Coast as being the most likely, so will continue
with 40 PoPs there and 20 percent from south Brevard to Okeechobee.

Otherwise it will be a little drier across the north and min
temps are expected in the lower 70s, with maybe even a few upper
60s around the Ocala National Forest. This would actually seem
quite pleasant after our long and muggy summer.

(from Previous Discussion)
Wed-Thu...Weak moisture convergence zone left over from old frontal
trough will keep PoPs elevated over our southern counties (Treasure
coast/Okeechobee). So will continue with PoPs there of 40 percent on
Wed and 50 percent Thu, which is a little below GFS MOS guidance.
Much drier air across the north (I 4 corridor) will produce a tight
PoP gradient and will keep rain chances out of the forecast both
days north of Orlando. There will be isolated storms, especially
Thu, when temps aloft cool a couple degrees.

Fri-Mon...Full attention will be on Hurricane Maria forecast by NHC
to be near the southeast Bahamas Fri. The 12Z GFS and ECMWF
models continue to show Maria lifting northward into a weakness in
the subtropical ridge carved out by trough trailing from Jose.
Though this will be well east of the local area, another round of
large swells impacting the coast can be expected this weekend
with high surf, a high risk of rip currents and additional beach
erosion.

Easterly flow should increase some and provide enough moisture to
produce showery precip Fri across all of EC FL with isolated
thunder. The weekend forecast will hinge greatly on the eventual
track of "Maria". But the current forecast calls for breezy NE
winds esp at the coast with small rain chances mainly near the
coast. Max temps in the M80s along the coast, upper 80s/near 90F
over the interior. Min temps L/M70s.

&&

.AVIATION...Mid level debris clouds eroded and allowed surface
heating to initiate shallow convection. The HRRR model is only
showing a small coverage of showers across the south interior.
Therefore, expect only a slight chance for MVFR-IFR conditions
through sunset south of KMCO-KTIX. Will have to watch coastal
TAFS, mainly KVRB-KFPR-KSUA for redevelopment of showers with
heavy downpours.

&&

.MARINE...
Tonight...Northeast swell train has continued and seas 7-8 feet
have persisted at buoy 41009. Additionally, east/northeast winds
have occasionally been 10-15 knots. Therefore, will continue with
an advisory for seas offshore and exercise caution statements
nearshore.

Wed-Sun...High pressure ridge to the north of the waters will
produce an onshore flow around 10 knots Wed and Thu, except 10-15
knots near a weak trough/convergence zone lingering over the
southern/central waters.

Even though Hurricane Maria will track to the north well east of our
waters, the pressure gradient will start to increase by Fri with
east winds around 15 knots expected. Winds from the northeast
15-20 knots are forecast over the weekend.

Swells may keep seas around 7 feet offshore into Wed, but as
"Jose" pulls farther away, expect seas to subside a few feet into
late week. Swells from Hurricane Maria should start to build seas
again by Saturday. With winds increasing slightly over the
weekend, Small Craft Advisories are likely as seas build to 7 feet
nearshore and 10-14 feet offshore by Sunday.

&&

.HYDROLOGY...
Minor to moderate flooding along the Saint Johns River near Cocoa,
Geneva, Sanford, Deland and Astor are forecast to change little
into late week. The Saint Johns River above Lake Harney near Geneva
is forecast to remain in major flood stage.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  72  88  73  87 /   0  10  10  10
MCO  73  91  73  89 /   0  20  10  20
MLB  75  87  75  88 /  20  30  30  50
VRB  74  87  74  87 /  30  40  30  50
LEE  72  93  73  91 /   0  10  10  20
SFB  72  91  73  90 /   0  10  10  20
ORL  73  91  74  90 /   0  10  10  20
FPR  74  87  73  87 /  30  40  30  50

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory for hazardous seas until 5 AM EDT Wednesday
     for Flagler Beach to Volusia-Brevard County Line 20-60 nm-
     Sebastian Inlet to Jupiter Inlet 20-60 nm-Volusia-Brevard
     County Line to Sebastian Inlet 20-60 nm.

&&

$$

Lascody/Weitlich



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