Special Marine Warning 545, NWS Miami, FL

Area Forecast Discussion
National Weather Service Miami FL
237 AM EST Sun Dec 19 2021

...Unsettled pattern to kick off Christmas week...

.SHORT TERM (Today through Monday)...
Near-surface (boundary layer) winds will veer out of the southeast
ahead of an approaching frontal cyclone. This will favor gradual
moisture advection and isentropic ascent, particularly along the
eastern half of the CWFA where greatest chances for convection
exist. PWATs around 1.6 to 1.8 inches, SFC to 6km bulk shear
values of 20-25 kt, and ML CAPE around 1000 J/kg may support a few
stronger shower/storms, though the absence of deep forcing will
generally limit overall convective coverage. The greatest chances
for experiencing a strong storm or two exist over the Atlantic
waters and adjacent coastline.

By late Sunday/early Monday, a stout cold front approaches the
region, remaining just north of the region during this period.
This will continue to favor S/SW boundary layer winds implying
enhanced moisture advection. Patchy fog may develop over the
interior, particularly near areas with lowest overnight
temperatures. Over the eastern Gulf of Mexico, a pronounced 250
hPa jet streak of 80-90 kt exists, and aligns favorably upstream
of a developing surface cyclone. There are subtle variations in
prognostic solutions, though a general consensus exists in that a
baroclinic system will introduce deleterious weather conditions as
early as Monday evening for the western half of the region.

.LONG TERM (Monday Night through Saturday)...
Monday Night through Tuesday

The primary feature of focus for this upcoming week (late
Monday/early Tuesday) is a baroclinic cyclone that is forecast to
deepen over the eastern Gulf of Mexico. A favorable negatively
tilted trough will develop upstream of the low, allowing for a
system characterized by enhanced temperature gradients to
materialize. Ahead of this system, ribbons of elevated theta-e
values advect northward at roughly 25 kt at 850 hPa, indicating
strong moisture transport. The shear environment will be favorable
for organized strong to severe thunderstorm development, as
effective bulk shear values around 40-50 kt may become realized.

Limiting factors to consider during this period will be:

1. A narrow open warm sector, which may only allow for a brief
chance for kinematics/thermodynamics to align

2. A limited thermodynamic environment, as gradual synoptic scale
ascent may act detrimentally by deepening cloud coverage and
hence limiting CAPE (instability) across the region

Bullish prognostic solutions suggest that a deep surface cyclone
may develop, namely the NAM, while the ECMWF/GFS remain a bit more
limited in terms of intensity and are slower to progress
eastward, resulting in a weaker surface cyclone. Ultimately the
former solution would be more favorable for strong/severe
thunderstorm development, though much uncertainty exists regarding
overall storm environment. Continue to monitor updates to the
forecast as greater clarity emerges.

Wednesday through Sunday

Cooler temperatures will become realized in the wake of the
aforementioned cold front passage, as a baroclinic surface high
builds in front the north. This will also favor drier conditions
region-wide, though a few low-topped and short-lived showers may
develop where lingering moisture converges. Temperatures may dip
below 50 degrees over portions of the interior Wednesday and
Thursday night, while maximum temperatures will be a more
seasonable through mid/late week (mid 70s).

&&

.AVIATION(06Z TAFS)...
Generally VFR conditions though coastal showers (and possible some
thunderstorms) remain a sub-VFR concern overnight that could
linger through the day. Patchy fog will be possible across the
interior and west coast this morning. Winds will increase by the
mid-morning and turn more southerly as the day progresses. At
APF, winds will shift to the southwest this afternoon as the Gulf
breeze moves inland. After sunset, winds should become lighter
with some variability.

&&

.MARINE...
A gradual moistening will occur as winds shift out of the
south/southeast. This will favor development of scattered/numerous
showers and a few thunderstorms, particularly over the Atlantic
waters. Locally elevated winds and seas may be experienced near
any ongoing showers or thunderstorms. Early this upcoming week, a
strong cold front will approach the region, with chances for
strong to severe thunderstorms possible ahead of this system. By
early/mid week, hazardous marine conditions may be experienced as
the front progresses through the region. SCA/SCEC may be warranted
during this period.

&&

.BEACHES...
Hazardous beach conditions remain for the Atlantic beaches, though
the high risk for rip currents reduces to an elevated risk, as
winds retain less of a direct onshore component. A strong cold
front will approach the region early this week, and hazardous
beach conditions could result from the passage of this system
later in the upcoming week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Miami            83  70  83  71 /  50  20  30  30
West Kendall     84  68  83  69 /  40  20  30  30
Opa-Locka        83  68  83  70 /  50  20  30  30
Homestead        82  68  82  69 /  50  20  20  30
Fort Lauderdale  83  70  82  70 /  40  20  30  40
N Ft Lauderdale  82  70  82  70 /  40  30  30  40
Pembroke Pines   83  68  83  69 /  50  20  30  40
West Palm Beach  82  68  81  68 /  50  30  30  50
Boca Raton       83  69  82  69 /  40  30  30  40
Naples           83  69  82  69 /  20  10  20  40

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 7 AM EST this morning for FLZ168-172-
     173.

AM...None.
GM...None.
&&

Today through Monday and Beaches/Marine...SRB
Monday Night through Saturday...SRB
Aviation...RAG

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Hazardous Weather Outlook for South Florida
National Weather Service Miami FL
410 PM EST Sat Dec 18 2021

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
191515-
Lake Okeechobee-Biscayne Bay-
Coastal waters from Jupiter Inlet to Deerfield Beach FL out 20 NM-
Coastal waters from Deerfield Beach to Ocean Reef FL out 20 NM-
Waters from Jupiter Inlet to Deerfield Beach FL from 20 to 60 NM-
Waters from Deerfield Beach to Ocean Reef FL from 20 to 60 NM
excluding the territorial waters of Bahamas-Glades-Hendry-
Inland Palm Beach-Metro Palm Beach-Coastal Collier-Inland Collier-
Inland Broward-Metro Broward-Inland Miami-Dade-Metro Miami-Dade-
Mainland Monroe-Coastal Palm Beach-Coastal Broward-Coastal Miami-
Dade-Far South Miami-Dade-
Coastal waters from Chokoloskee to Bonita Beach FL out 20 NM-
Coastal waters from East Cape Sable to Chokoloskee FL out 20 NM-
Waters from Chokoloskee to Bonita Beach FL from 20 to 60 NM-
410 PM EST Sat Dec 18 2021

...High Risk of Rip Currents East Coast Beaches...
...Patchy Fog Possible Interior Sections Late Tonight...

This hazardous weather outlook is for South Florida.

.DAY ONE...TONIGHT

Thunderstorms: A thunderstorm or two may develop, mainly over the
Atlantic waters. Lightning is the primary associated hazard.

Rip Currents: There is a high risk of rip currents across all
Atlantic beaches.

Visibility: Patchy fog may develop over portions of the interior and
the Lake Okeechobee region late tonight. Visibilities may drop down
to a mile or less in some spots.

Waterspouts: There is a slight chance of waterspouts over the
Atlantic waters.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

An elevated risk of rip currents may persist throughout the rest of
the weekend across the Atlantic Coast beaches.

A cold front will approach South Florida by this upcoming Tuesday.
Ahead of this front, the chances for thunderstorms will increase. A
strong thunderstorm or two containing gusty winds and heavy downpours
cannot be ruled out on Tuesday.

Deteriorating marine and beach conditions, including increasing
swell and building seas, are possible across the local waters on
Tuesday into Wednesday as a cold front pushes through the area.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

For more information...visit the National Weather Service in Miami
website at www.weather.gov/miami.