Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 201731
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
1231 PM EST Fri Jan 20 2017

.AVIATION...
VFR conditions expected to continue through the TAF period at all
terminals. South-southwesterly winds between 6-10 KT will prevail
along the east coast TAF sites this afternoon, then return to
light and variable early this evening. A weak gulf sea breeze will
affect APF through the evening hours.

&&

.PREV DISCUSSION... /issued 959 AM EST Fri Jan 20 2017/

UPDATE...

Increasing Potential for Strong to Severe Storms Late
Sunday and Sunday Night...

Broad high pressure remains across the state with light and
variable flow continuing @author the rest of the morning hours.
Winds become a little stronger and switching to a more southerly
flow this afternoon. Little to no rain activity is expected today
as a relatively stable airmass remains in place through Saturday.
Latest model data insists in bringing a vigorous cold front
boundary across South Florida from late Sunday into early Monday,
with potential for severe weather, localized heavy rain and even
an isolated tornado.

PREV DISCUSSION... /issued 429 AM EST Fri Jan 20 2017/

Increasing Potential for Strong to Severe Storms Late
Sunday and Sunday Night...

DISCUSSION...

Today through Saturday: High pressure centered to our south and
east will keep the region under light south-southwest flow. Weak
upper level ridging along with the surface high will limit the
southward progress of the cold front currently over north Florida,
keeping it nearly stationary and keeping the weather over South
Florida dry and mild. Patchy fog will be a concern the next two
nights, especially over the interior, as flow becomes a little
more southwest. However, the increasing low level flow may trend
more towards stratus Saturday night.

Sunday-Monday: Ingredients are coming together for a strong to
severe storm threat across South Florida late Sunday evening through
early Monday morning.

A closed upper level low is expected to develop over Texas Sunday
morning, embedded in a larger broad through across the central US.
The upper level low is forecast to slide across the deep South
during the day on Sunday, and eventually up the eastern seaboard
into Monday, as a 130-140kt jet across the Deep South helps dig the
trailing trough across the eastern Gulf and Florida.

Surface low develops across the Texas Panhandle Sat night with the
upper level low, sliding east interacting with the stalled
frontal boundary along the northern Gulf coast into Sunday. How
much activity we see during the day on Sunday will likely depend
on how much convection develops over the eastern Gulf of Mexico
early in the day, with higher amounts increasing cloud cover and
limiting heating. Breezy southwest flow will also make Sunday the
mildest day with temps reaching into the low-mid 80s.

Models are still hinting the stalled boundary moving south as a
robust pre-frontal trough Sunday evening, followed by the actual
cold front clearing South Florida after daybreak Monday.

With a 100-110kt jet moving across the FL peninsula on the south
side of the upper level low Sunday night, models are showing
impressive 925mb and 850mb winds of 40-55kt across the region. Both
the GFS and ECMWF show low level flow veering quickly southwest
during the evening, which would tend to closed upper level low is
expected to develop over Texas Sunday morning, embedded in a
larger broad through across the central US. The upper level low is
forecast to slide across the deep South during the day on Sunday,
and eventually up the eastern seaboard into Monday, as a
130-140kt jet across the Deep South helps dig the trailing trough
across the eastern Gulf and Florida.

Surface low develops across the Texas Panhandle Sat night with the
upper level low, sliding east interacting with the stalled
frontal boundary along the northern Gulf coast into Sunday. How
much activity we see during the day on Sunday will likely depend
on how much convection develops over the eastern Gulf of Mexico
early in the day, with higher amounts increasing cloud cover and
limiting heating. Breezy southwest flow will also make Sunday the
mildest day with temps reaching into the low-mid 80s.

Models are still hinting the stalled boundary moving south as a
robust pre-frontal trough Sunday evening, followed by the actual
cold front clearing South Florida after daybreak Monday.
 favor damaging winds as the main severe weather threat. However,
isolated tornadoes and waterspouts can not be ruled out. The
latest Day 3 outlook from SPC has placed all of South Florida
under a slight risk for severe weather for Sunday night into early
Monday.

Tuesday Onwards: Surface high pressure center in the wake of the
front quickly slides across South Florida into Wednesday and winds
become south-southeast. Forecast looks dry Tuesday-Thursday, with
rain chances creeping back into the forecast late week as another,
much weaker front, looks to approach the region. Highs cool into the
mid 70s, or near normal for this time of year on Tuesday, then back
into the upper 70s/low 80s for the remainder of the week. Coolest
overnight lows will be Tuesday night in the 50s to low 60s.

MARINE...Quiet conditions under southerly flow are expected
through Saturday across the local Gulf and Atlantic waters.
Southerly winds increase to 15-20kts ahead of an approaching cold
front Saturday night, then deteriorate rapidly Sunday afternoon
with the front, becoming southwest 20-25kts. Showers and storms
will move into the region along and ahead of a strong cold front
with potential for a few strong-severe storms. The front is
expected to clear South Florida around daybreak Monday. Winds veer
west- northwest 25-20kts behind the front with potential for gale
force gusts through late Monday. If trends continue, a Gale Watch
may be issued for this period later today or tonight.

With gusty winds, seas build rapidly Sunday afternoon to 8-12ft in
the Gulf and Atlantic waters by Sunday night, peaking on Monday 12-
16ft in the offshore Gulf and 8-11ft in the offshore Atlantic
waters. Conditions will slowly improve on Tuesday as winds
subside.

BEACH FORECAST...Beach conditions are forecast to quickly erode
on Sunday, as winds increase ahead of a cold front. This would
bring a high risk of rip currents to the Gulf coast beaches from
Sunday through Monday evening, and possibly Tuesday morning. It
will also lead to the potential to beach erosion and even some
minor coastal flooding, especially in flood prone coastal areas
along the Gulf coast.

On the Atlantic side, a west wind would not typically cause any
issues. However, if the wind reaches 25 to 30 kts, it could cause
some reflection of the waves off the Bahamas, which could lead to
some risk of rip currents for the Atlantic beaches, possibly late
Monday into Tuesday.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  65  81  70  85 /   0   0  10  30
Fort Lauderdale  68  79  71  83 /   0   0  10  20
Miami            68  79  70  83 /   0   0  10  30
Naples           64  82  69  80 /  10   0  10  50

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.
&&

AVIATION...17/AR






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