FXUS62 KMLB 201939

Area Forecast Discussion
National Weather Service Melbourne FL
339 PM EDT Wed Sep 20 2017


Tonight-Thursday...The only change with the pattern is that onshore
flow will pick up slightly on Thu as a high pressure ridge to the
north starts to nudge northward while Hurricane Maria slowly gains
latitude near Hispaniola. The GFS continues to show an area of
higher moisture across our south half (remnants from old, old
trough/front). The slightly increased low level flow should push a
few more Atlantic showers ashore tonight mainly along the Treasure
Coast, but PoPs still look to be only around 20 percent. On Thu,
expect chance PoPs there and a slight chance into south Brevard. MOS
values have been a bit on the high side the past few days, but
with a little more gradient wind, moisture convergence should
support 30-40% values, which is still below MOS.

Will retain mention of slight chance for storms Thu as mid level
temps are forecast to cool about a degree. Thunder chances along the
coast would probably be during the morning to early afternoon, then
shifting inland.

Friday-Saturday...Major Hurricane Maria is forecast to be just north
of Haiti/Dominican Republic early Friday morning and is forecast to
continue moving NNW and eventually north by early Saturday. Latest
NHC forecast still keeps Maria well to the east of Florida with the
main impacts for east central Florida being along the coast in the
form of a high rip current risk, high surf, and beach erosion due to
large swells coming in.

With Maria well to the south and east the local wind field in the
lower levels will remain onshore and easterly. Increasing moisture
across the area along with cooling temperatures aloft should support
a chance of showers and some storms areawide for Friday and
Saturday. Have compromised between the GFS and ECMWF PoPs for
Friday at around 50% with the GFS being the more aggressive of the
two. The models are in better agreement for precip chances on
Saturday with most areas seeing chance PoPs at 50%. The pressure
gradient will tighten on Saturday resulting in an increase in winds
with breezy conditions expected along the coast.

High temperatures will be mid to upper 80s most locations and
approaching 90 over the interior. Lows continue to be low to mid 70s
with perhaps upper 70s Saturday morning along the coast with the
strengthening onshore flow.

Previous Discussion...
Sun-Tue...As "Maria" lifts north of our latitude Sunday, northerly
flow will advect a drier airmass down into the area so rain chances
will decrease to 20 percent or less through early next week. Have
also removed any thunder. The pressure gradient will weaken
considerably as "Maria" pulls away so winds will become quite light
Mon-Tue. High temps will be near climo in the upper 80s/near 90.

Dangerous surf and rip currents will continue at the beaches
through early next week.


.AVIATION...Conditions will most be VFR. There's a small chance
for MVFR tonight from about KMLB-KSUA as Atlantic showers drift
into the coast. This same area should have a little greater chance
for showers on Thu.


Tonight-Thursday...Weak onshore flow should increase slightly on
Thu as the pressure gradient tightens a bit in response to
Hurricane Maria beginning to slowly gain latitude into the
Atlantic basin. Speeds should pick up to 10-15 knots in the
offshore waters south of Cape Canaveral Thu afternoon. Seas will
be slow to subside tonight due to lingering swells from Jose, so
exercise caution statements will still linger over the Gulf

Fri-Sat...Gradually deteriorating boating conditions Friday into
Saturday due to large swells coming in from Major Hurricane Maria.
Easterly winds of 10-15 kt nearshore with 15-20 kt for the
offshore waters. For the nearshore waters seas 3-5 feet will build
to 5 to 7 feet by Saturday evening. Offshore waters can expect
seas of generally 4-7 feet on Friday building to 8-11 feet by
Saturday evening.

Sun-Mon...Hurricane Maria will track north of our latitude, well
east of our waters. The models seem to be trending slightly farther
east, but north-northeast winds might still be 15-20 knots Sunday
then diminish a little Monday. The latest Wave Watch 3 model shows
waves peaking lower, around 12 feet. Still, long period swells
and wind waves will create hazardous conditions Sunday with only
slowly subsiding seas expected Monday.


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


DAB 73 87 74 86 / 0 10 30 50
MCO 73 91 73 89 / 0 10 20 50
MLB 75 87 76 88 / 10 20 30 50
VRB 74 87 75 88 / 20 40 30 50
LEE 73 92 74 90 / 0 10 10 50
SFB 73 91 73 89 / 0 10 20 50
ORL 74 90 75 89 / 0 10 20 50
FPR 74 87 75 88 / 20 40 30 50




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