Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 261408
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
1008 AM EDT Mon Oct 26 2020

.Update...
High pressure in the mid levels across Central Florida has led to
quite a bit of drying and warming in the mid and upper levels, as
noted in the 12z Miami sounding. The drying is mainly above 500
mb, although there are hints of drying and subsidence in the
700-500 mb layer. As a result, very little in the way of
precipitation over South Florida and the local waters this
morning, especially compared to the past few days. There is still
quite a bit of moisture below 700 mb and a noticeable precipitable
water gradient between Lake Okechobee (1.6 inches) and the Miami
area (2.1 inches) based on GOES-16 Total Precipitable Water data.

High-resolution, convective allowing models seem to be a bit too
wet over SE Florida later this morning and midday and there`s no
apparent evidence of added moisture upstream over the Straits of
Florida this morning. Therefore, current thinking is that the
mid/upper level drying and associated subsidence will likely limit
coverage of showers and thunderstorms the rest of today over the
east coast areas, therefore lowered PoPs some over those areas.
The bulk of the showers and scattered thunderstorms is expected
over the western half of the peninsula this afternoon in the
prevailing SE flow, but don`t anticipate any real strong storms
due to the rather stable mid levels.

The Flood Watch expires at 8 PM today, and if current trends hold,
the watch should be able to be expired later today.

&&

.Prev Discussion... /issued 738 AM EDT Mon Oct 26 2020/

Aviation (12z TAFs)...
A few SHRA in the vicinity of east coast terminals through
18z/20z, with any periods of MVFR conditions being brief. VCTS
included at KAPF for the 18z-00z time frame with period of MVFR
there as well as showers and thunderstorms increase over the
interior and western peninsula. Otherwise VFR conditions to
prevail. SE wind 10-15 knots, occasionally gusting near 20 knots.

Prev Discussion... /issued 310 AM EDT Mon Oct 26 2020/

.FLOOD WATCH EXTENDED THROUGH MONDAY FOR ATLANTIC METROS...

Short Term (Today through Tuesday Evening)...

A 500 hPa short-wave trough ejects out of the region into the
western Atlantic, as a ridge of higher pressure builds in over
South Florida. Modest boundary layer moisture remains in the
trough`s wake, which may support scattered convective activity
through Monday. With a subtle turning of the near-surface winds
from SSE to SE, the majority of convective coverage should develop
over the interior and possibly closer to the Gulf coast.
Localized flooding still remains a threat if showers/thunderstorms
are slow to propagate over recently saturated areas.

By Tuesday, the aforementioned ridge of high pressure
consolidates and progresses a bit eastward such that the 500 hPa
center is located offshore of the northern Florida state border.
With South Florida in the southern quadrant of this feature, near-
surface easterly flow will preside, which will transport
relatively drier air over the region. Given the lack of deep
tropospheric moisture and subsidence aloft induced by the ridge,
storm coverage will be limited Tuesday, with PoPs no greater than
30 across most of the area.

Maximum temperatures will be seasonable, with most areas
experiencing highs in the mid/upper 80s. The Gulf coast could see
temperatures in the low 90s Tuesday as the ridge builds over the
area.

Long Term...

Wednesday through Friday...

Stout ridging will be situated aloft for the first half of the
extended period. This should allow for enhanced subsidence and
drier mid-level air to suppress widespread convection across South
Florida. Although, southeasterly flow in the boundary layer will
keep sufficient enough moisture in the lower levels to support a
few light, garden-variety showers. Therefore, a slight chance of
rain remains in the forecast, mainly over the interior sections
during the afternoon and evening hours.

Saturday through Monday...

Dry season conditions are sadly disrupted, as a sharp trough digs
across the CONUS, shifting the mid-level ridge eastward into the
Atlantic. As the trough traverses through the westerlies and
interacts with the remnants of what is currently Tropical Storm
Zeta, guidance depict cyclogenesis across the Southeast/Central
Plains. Both the GFS and the ECMWF show the developing surface low
moving northeastward into the mid Atlantic, dragging an attendant
cold front down the FL Peninsula. Latest solutions continue to
hint at the first passage of the season for South Florida, albeit,
nothing to be too excited about as quickly veering winds out of
the northeast will modify any continental air back to maritime.

Ahead of the boundary, southerly flow will support the return of
showers and thunderstorms across the region before the frontal
boundary becomes stationary across the Florida Straits. Given
this is still towards the end of the period, uncertainty remains
rather high regarding the evolution and final destination of the
late week frontal boundary. Therefore, will continue to be monitor
each forecast cycle.

Daytime temperatures will generally range from the mid to upper 80s,
with overnight lows dipping into the 70s.

Marine...
Modest east-southeast/southeast flow will continue over the
waters, as pressure gradient tightens between a high pressure
ridge to the north and Tropical Storm Zeta in the NW Carribean
waters. A NE swell will continue mainly over the nearshore waters
of Palm Beach with a gradual decay through the week.
Isolated/Scattered shower and thunderstorm activity may persist
today, but will decrease in overall coverage through the week.
Winds and seas may be locally higher nearby any active storm.

Aviation (06Z TAFs)...
VFR conditions should prevail this morning and through most of
the day. ISLD/SCT convection may temporarily reduce VIS/CIGs to
MVFR and possibly brief IFR thresholds. Any showers that do
develop over eastern sites will be generally short-lived and
quick-moving, and widespread coverage is not anticipated. The
interior and Gulf coast may be more prone to storm activity, due
to prevailing SE flow.

Beach Forecast...
Swell emanating far downstream from Hurricane Epsilon and
persistent east-southeast/southeast surface flow will combine to
produce hazardous beach conditions, with an elevated risk of rip
currents being the main concern. Beach conditions may deteriorate
over the Gulf coast as well due to downstream effects from
Tropical Storm Zeta. Surf heights will generally be 2-4 feet over
coastal Atlantic waters, however cannot rule out building Atlantic
surf to 5-6 feet, particularly along the Palm Beaches.
&&

.Preliminary Point Temps/PoPs...
West Palm Beach  86  76  87  76 /  20  20  20  10
Fort Lauderdale  85  78  88  78 /  30  20  20  10
Miami            87  78  88  78 /  40  20  20  10
Naples           88  76  90  76 /  60  30  30  10

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch until 8 PM EDT this evening for FLZ068-072>074-168-
     172>174.

     High Rip Current Risk through Wednesday morning for FLZ168-172-
     173.

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

Update...59/RM








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