Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 122049
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
349 PM EST Tue Dec 12 2017

.DISCUSSION...

TONIGHT THROUGH THURSDAY: Dry frontal boundary is crossing through
North Florida this afternoon. As expected, it`s main impact today
has been a modest moistening in the low levels. This has lead to a
cumulus field pushing across the peninsula out ahead of the
front. Upstream soundings show PWATs still struggling to get to
0.50", with just enough moisture around 4KFT for the cumulus
field.

Breezy west winds will continue through the remainder of the
afternoon ahead of the front, with the front itself crossing South
Florida overnight. The combination of a little more moisture and
higher winds will keep overnight lows a little warmer in the 40s and
low 50s.

High pressure builds east across the Gulf and FL peninsula behind
the front, with NW flow reinforcing the cool and dry airmass across
the state. High temperatures on Wednesday will once again been 10 to
15 degrees below normal, struggling to get out of the 60s. With the
high directly overhead Wednesday night, winds should quickly become
calm by sunset. Under clear skies with dewpoints forecast to drop
into the mid to upper 30s across the region, there is no reason that
low temperatures Wednesday night will not dip back into upper 30s
for much of interior South Florida, with low 40s for the Palm Beach
and Gulf coasts. The remainder of the east coast metro will likely
remain in the 40s, though the immediate coastal areas may stay
around 50.

By Thursday, flow begins to back more westerly ahead of the next
system allowing a little more moisture return. This will keep
temperatures a little warmer in the upper 60s and low 70s during the
day with overnight lows in the mid-upper 50s.

FRIDAY THROUGH THIS WEEKEND: The GFS and ECMWF solutions have come
into better agreement regarding the front for late this week. Both
are now a little more robust with the upper level ridge, keeping the
shortwave sliding across the Deep South well north. The associated
surface front now looks to struggle to make it into Central FL, let
alone South Florida. However it still looks to generate enough lift
and instability ahead of the front for a few showers over the whole
CWA late Friday into Friday night. Given current trends, some rain
threat may linger into Saturday as the boundary washes out around
Lake Okeechobee.

&&

.MARINE...Ongoing gusty westerly winds will continue into this
evening, shifting northwest late tonight as a dry front pushes
through. Advisory conditions will continue over the Gulf waters
this afternoon, with winds expected to reach criteria over the
Atlantic waters this evening. High pressure quickly rebuilds
across the state on Wednesday with diminishing winds becoming
west-southwest 10kts or less into Thursday.

Seas peak late tonight around 5-7ft in both the Gulf and Atlantic,
subsiding to 2-4ft by Wednesday night.

&&

.AVIATION...VFR will prevail through the period. W-WNW winds to be
strongest late this afternoon, possibly as high as 12-15 knots
gusting to 22 knots for several east coast terminals. Behind the
front, winds will gradually shift to NW over the course of a few
hours tonight in the 320-340 degree range. Winds around 7-9 kts from
the NW-NNW will prevail from late tonight well into Wednesday.

&&

FIRE WEATHER... Breezy westerly flow continues through the remainder
of this afternoon with RH values expected to remain above critical
levels. A dry front will push through the region overnight with high
pressure building overhead on Wednesday. The resulting light winds
will lead to very poor dispersions, with the reinforcing dry
airmass allowing RH values to drop below critical thresholds for
several hours tomorrow afternoon. ERC values are expected to
remain below critical levels for RH duration.

While winds will remain light, RH improvement is expected through
the remainder of the week as another system approaches the region
with a little more low level moisture.

&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  47  65  45  71 /   0   0   0   0
Fort Lauderdale  51  66  49  72 /   0   0   0   0
Miami            52  67  50  70 /   0   0   0   0
Naples           48  65  48  72 /  10   0   0   0

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory from 7 PM this evening to 7 AM EST
     Wednesday for AMZ650-651-670-671.

GM...Small Craft Advisory until 4 AM EST Wednesday for GMZ656-657-676.

&&

DISCUSSION...88/ALM
MARINE...88/ALM
AVIATION...98/ABH
FIRE WEATHER...88/ALM




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