Area Forecast Discussion
Issued by NWS Melbourne, FL

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FXUS62 KMLB 150904

Area Forecast Discussion
National Weather Service Melbourne FL
400 AM EST Sat Dec 15 2018


Current...A closed mid/upper level low over MS/AL is continuing to
gain latitude as it heads east northeast toward the Tennessee
Valley. Large-scale ascent well to its southeast continues to
support a NNE/SSW oriented band of showers with embedded storms over
the central and southern peninsula. Still, given that the line
continues to move further away from its support and into rather
meager instability, both its areal extent and intensity has been on
the downward trend early this morning.

Today-Tonight...As the closed low continues to migrate northeast
toward the Mid Atlantic, an associated pre-frontal surface trough
will shift across the area and gradually scour out lingering
moisture. While most of the activity associated with the lead
convective band will be offshore by sunrise, opportunity for mainly
light to moderate rain showers will continue through the day, at
least until the mid/upper level trough axis passes overhead. Both
ECMWF and GFS MOS guidance indicate likely PoPs throughout the area
today; however, their corresponding QPF is quite low.

Any lingering showers will scour out this evening from NW to SE as
the mid/upper level trough axis shifts into the Atlantic. Weak cool
air advection behind the surface feature will bring temperatures
closer to seasonable levels, but still a couple degrees above mid-
December climo.

Sunday-Tuesday...Zonal mid-upper flow will take hold of the local
pattern through early week, in the wake of the rapidly departing
deep layer low. A strung out cyclonic shear axis at the base of a
broad northern stream trough will brush north Florida Monday night
but be of no consequence in terms of sensible weather. Surface winds
will veer from westerly during the day on Sunday to northwest from
Sunday night through Monday evening as high pressure and cooler,
drier air builds into Florida behind a departing cold front. Maxes
Sunday in the U60s north to M70s south, then turning cooler with
mins Sunday/Monday nights in the U40s to around 50F. Maxes in the M-
U60s Monday and L70s for most of the areas on Tuesday. Mins a little
milder (50-55F) Tuesday night.

Wednesday-Saturday...While still 5-6 days out in time, global models
continue to trend toward another high amplitude short wave trough or
closed low impacting the SE CONUS and Florida late next week. Short
wave troughing in both the northern and southern streams is forecast
to come into phase over the southern MS valley early Thursday, with
the resultant deep trough backing the flow aloft over the SE CONUS
and FL. Setup looks similar to earlier events this month: Increasing
forced ascent lowers surface pressures over the N-NE GOMEX, with SE
low-mid level flow veering southerly and strengthening between a
developing storm system and retreating high to its east. Confidence
that at least some semblance of a system will impact the local area
is increasing, given the trend toward better consensus in the pattern
both at the surface and aloft.

Still, at this long of a time frame, we have this weekend and the
first half of next week to watch model trends on the evolution of
this potential system. Have nudged POPs up Wednesday night through
Thursday night, but am still below the guidance consensus for now.
Temps will trend to near or slightly above normal.


.AVIATION...A north-to-south oriented band of convection with brief
IFR VSBYs/CIGs will continue to push across the Treasure Coast
terminals (KVRB-KSUA) early this morning. Lingering moisture behind
this feature will maintain a chance for -SHRA today along with MVFR
CIGs. Moisture will scour out from the NW to SE late this afternoon
and this evening and lead to steadily improving conditions.



Today-Tonight...A weakening line of showers and embedded isolated
storms will shift offshore the Treasure Coast this morning. This
feature is in association with a pre-frontal trough that will move
over the waters and shift winds generally to the west at 10-15
knots. As a result, steadily improving marine conditions are
forecast; however, small craft should still exercise caution this
morning over the offshore waters for seas up to 6 feet.

Sunday-Wednesday...Winds and seas gradually subside from early to
the middle of next week. Moderate offshore flow will gradually
slacken as it veers from NW Sunday-Monday to NE Tuesday and E-SE
Wednesday. Seas 3-5FT early Sunday subsiding to 2-3FT from Monday
evening onward.


.FIRE WEATHER...No critical wind or RH concerns.


DAB  71  55  67  48 /  40  10   0   0
MCO  71  57  70  50 /  30  10   0   0
MLB  75  59  71  51 /  30  10   0   0
VRB  76  59  73  51 /  50  10  10  10
LEE  71  56  68  48 /  40  10   0   0
SFB  72  57  69  50 /  30  10   0   0
ORL  72  57  70  50 /  30  10   0   0
FPR  77  59  73  50 /  50  20  10   0





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