Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 182000
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
300 PM EST Sat Nov 18 2017

.DISCUSSION...

Tonight-Sunday...Surface high pressure ridge across central Florida
will gradually sag farther across south Florida with light WSW to SW
return flow developing across the northern/central CWA through late
tonight. A fast moving cold front will reach the northernmost CWA
around noon-1PM, with what will likely be a narrow and weakening
band of showers along and immediately behind it. Boundary is progged
to lie across the southern CWA, somewhere between southern Osceola/
Brevard Counties and Okeechobee-Fort Pierce by 7 PM. Tried to refine
timing of best shower chances (30-40), which will be across the
north-central CWA through mid day, with overall coverage (20 percent
chance or less) decreasing as the front reaches the southern CWA,
ending north-central late.

Mins tonight will be a degree or two either side of 60F. Maxes will
range from near 75F across the north to the L80s south.

Monday...A pleasant day is in store for Monday with the atmosphere
continuing to dry out as the cool front continues to push south of
the area.  Low-level high pressure establishes itself over the
Carolinas turning winds out of the east-northeast.  Conditions will
be breezy during the afternoon as the pressure gradient tightens and
higher winds mix down from aloft.  An isolated shower is possible
for Martin county late in the day on Monday as moisture begins to
increase but have opted to leave the forecast dry for now. High
temps will be in the low to mid 70s.

Monday night and Tuesday...Low-level high pressure slides east over
the Atlantic veering the low-level flow to a more southerly to
southeasterly component resulting in pretty stout moisture return.
Both the GFS and ECMWF depict a shortwave trough moving across the
Gulf Coast Tuesday morning and an inverted trough/weak surface low
over the northeastern Gulf of Mexico.  The weak surface low is then
forecast to move across north Florida during the afternoon and
evening on Tuesday.  This combined with the enhanced moisture and
impulses of shortwave energy aloft will lead to high rain chances
areawide. The best chance (70%) will be north of line from Orlando
to the Cape due to proximity of the surface low and where omega
values are quite high along with impressive upper-level divergence.
Rain chances taper off gradually farther south (but still 50-60%) as
distance from the weak surface low increases.  Have also included a
slight chance for thunderstorms with temperatures at 500 mb between -
12 and -14 C.

Wednesday-Saturday...An increasingly amplified pattern will keep
conditions unsettled, though considerable uncertainty in the
synoptic details remain. Guidance generally agrees that multiple
pieces of mid/upper level energy will shift down the Rockies/Plains
and carve out the base of a larger scale trough over the Gulf.
Differences emerge in the strength/extent of the trough, with the
latest GFS (and to a lesser extent the ECMWF) consolidating much of
the energy into a closed low over the northeastern Gulf by Thursday.
Continue to advertise PoPs from mid to late week as consensus
suggests multiple opportunities for precipitation, particularly on
Thursday. However, given the low predictability environment,
especially in the timing of individual synoptic features, will
continue to cap precip chances at 50%.  Cloud cover will keep max
temps in the mid 70s through late in the week before a front cools
things by next weekend.

&&

.AVIATION...VFR. For now, opted to leave mention of MIFG/BR out of
the forecast except for a brief period pre-sunrise (09Z-12Z) @KLEE.
northerly wind shift will likely reach LEE-DAB right around 18Z, as
implied by the 20Z FROPA @KMCO (into the H24-30 period of their TAF).

&&

.MARINE...

Tonight-Sunday...Light southerly flow will become SW-WSW late
tonight, with the FROPA and attendant northerly wind shift reaching
the northern and central Marine legs during the afternoon.
Wave model guidance continues to run a bit high compared to buoy
obs, especially the NWPS. Used a slight reduction of the WNAWAVE
which yielded, sea around 3FT through early Sunday morning,
increasing to 3-4FT in the afternoon.

Monday-Tuesday...Poor to hazardous boating conditions as winds will
be east-northeasterly at around 20 kt offshore and 15-20 kt
nearshore.  Seas of 3-5 feet nearshore will build to 5-7 feet Monday
afternoon into overnight Monday.  Seas of 5-6 feet in the offshore
waters will continue to build to 7-8 feet by Tuesday morning.  Winds
and seas gradually diminish through the day on Tuesday, but high
rain chances along with a few thunderstorms will keep conditions
less than favorable.

Wednesday-Thursday...Low confidence forecast in the extended as
guidance indicates multiple weak troughs or lows in vicinity of our
waters. Gentle breezes expected Wednesday before some increase on
Thursday as low pressure becomes better organized. Confidence in
wind direction remains lower than usual at this time. Seas subside
to 3-5 feet by Wednesday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  61  75  50  71 /   0  40   0   0
MCO  61  78  51  73 /   0  30   0   0
MLB  62  80  57  74 /   0  30  10   0
VRB  61  81  61  74 /   0  20  20  10
LEE  62  75  48  73 /   0  40   0   0
SFB  61  77  51  73 /   0  40   0   0
ORL  61  77  52  72 /   0  40   0   0
FPR  60  80  60  75 /   0  20  20  10

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&

$$

SHORT TERM/AVIATION...Cristaldi
MID TERM...Combs
LONG TERM...Ulrich
IMPACT WX...Ulrich/Rodriguez


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