Area Forecast Discussion
Issued by NWS Melbourne, FL

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266
FXUS62 KMLB 222006
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
306 PM EST Wed Nov 22 2017

.DISCUSSION...

...High Rain Chances for Thanksgiving Day into Friday...

Rest of Today/Tonight...Stable northeast flow behind a weak frontal
boundary will keep the area dry this evening as attention shifts
toward developing low pressure over the central and eastern Gulf.
The stationary front currently just south of the Treasure Coast will
begin to lift north overnight, veering winds to the east and then
southeast. Weak convergence along the boundary will combine with
moisture pushing off the Atlantic to support small (20-30%) rain
chances along the coast during the overnight.

Thanksgiving Day...All of the ingredients appear to be coming
together for a "turkey" of a weather day in east central Florida.
Low pressure consolidating out ahead of a sharpening mid/upper level
trough will shift slowly into the eastern Gulf of Mexico by the end
of the day. Enhanced lift on the ascendant side of the trough and
from the right entrance region of an upper jet will provide the
necessary support aloft, while low level surface convergence
accompanies the front that should stall out near the Interstate 4
corridor by late morning. With that in mind, expect the greatest
coverage of precipitation to be across our northern areas. However,
even areas further to the south will likely see precipitation at
some point during the day. Rain chances in association with these
features will start before sunrise over Lake County, and then spread
steadily south and east through the remainder of the day.
Considerable cloud cover and weak wind fields suggest the threat for
severe weather is negligible, however, temps aloft remain cool and
will support deep convection capable of producing dangerous cloud to
ground lightning strikes.

Thursday night-Friday...A trough aloft extending well southward
into the Gulf of Mexico will slowly translate eastward while
gradually filling. At the surface, rather weak low pressure
along a quasi-stationary frontal boundary over the eastern Gulf
will eventually push across central FL by Fri night and pull the
frontal boundary through the area. The ECMWF shows the low
pushing to our east about 12 hours earlier though, so some model
differences have shown up on the 12z run.

Low pressure moving out of the Gulf and across FL always gets our
attention for severe weather potential. In this case, considerable
clouds will limit heating/instability while low level winds/shear
will not be particularly strong. Nonetheless, temps aloft will be
cold (-12C to -14C at 500mb) so cannot rule out a few strong
storms.

MOS POPs continue high each forecast period, in the categorical
range, and the synoptic setup is certainly supportive. Our
numbers for Fri (60 percent) represent a model blend as the faster
ECMWF movement of low pressure would bring drying earlier. The
highest rain amounts should be across our northern sections, along
and to the north of the low pressure track.

Saturday-Wednesday...A cooler and drier airmass will overspread the
area this weekend behind initial front Fri night/early Sat and
probably a reinforcing surge late Sun. The models quickly veer
the low level flow to onshore on Mon. Max/min temps look to be
only a few degrees from average (which are mid-upper 70s and mid-
upper 50s). The breezy onshore flow may start to push a few
Atlantic showers ashore Mon. As is typical for these return flow
cases, the early week MOS POPs are quite low, but will maintain
some slight shower chances for now.

&&

.AVIATION...Continued VFR through early Thursday morning. A warm
front will lift north overnight, providing a chance for SHRA at
the coastal TAF sites and for low stratus over inland aerodromes.
Have opted to include VCSH along the coast and MVFR cigs across
the interior for now, however, confidence in the evolution of the
stratus is low. Rain chances increase considerably around sunrise
Thursday as numerous showers and isolated thunderstorms push
inland from the Gulf of Mexico. Deteriorating CIGs/VSBYs expected
during the day as the showers spread to the south and east through
the day.

&&

.MARINE...
Rest of Today/Tonight...Northeast winds around 10-15 knots will veer
to the east and then southeast as a stationary frontal boundary over
the Treasure Coast begins to lift back north as a warm front. Seas 3-
4 feet nearshore and 5 feet offshore.

Thanksgiving Day...Low pressure will organize over the eastern Gulf
of Mexico, generating numerous showers and isolated thunderstorms
that will spread from west to east across the peninsula through the
day. Winds out of the south to southeast between 10-15 knots will
support 3-4 feet seas nearshore and up to 5 feet offshore.

Fri-Weekend...Wet weather is forecast Fri as a weak low pressure
center over the eastern Gulf of Mexico moves across central
Florida. Winds should be less than 10 knots, except 10-15 knots in
the Gulf Stream but they could be strong/gusty near numerous
showers and isolated storms.

Low pressure will shift northeast by Fri night and drag a cold
front through the waters. Post frontal winds on Sat out of the
northwest look to be around 15 knots then a reinforcing surge of
northerly winds late Sun is indicated with similar speeds. So
while the weather will improve over the weekend, winds look poor
for small craft operation, especially in the Gulf Stream, where
seas to 6 feet are expected.

Mon...High pressure building to the Carolina coast will generate a
breezy northeast-east wind flow and choppy conditions will occur
on all of the Atlantic waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  65  73  64  74 /  30  80  70  60
MCO  65  75  65  75 /  20  80  70  60
MLB  68  78  65  78 /  20  80  60  60
VRB  67  78  65  78 /  30  70  60  60
LEE  64  73  63  73 /  30  90  70  60
SFB  64  74  64  75 /  30  80  70  60
ORL  64  74  65  74 /  20  80  70  60
FPR  67  78  63  79 /  20  70  60  60

&&

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

$$

SHORT TERM...Ulrich
LONG TERM....Lascody



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