Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 241200
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
800 AM EDT Sun Sep 24 2017

.AVIATION...
Morning convection along the east coast will spread westward
throughout the day. Boundary collisions over the interior will
create a convective focus. Sub-VFR conditions are possible at any
sites impacted directly and short-fused amendments will be
necessary to account for changes in conditions. Overnight,
convection along the east coast will once again be possible.

&&

.PREV DISCUSSION... /issued 415 AM EDT Sun Sep 24 2017/

DISCUSSION...

TODAY AND TONIGHT: Large, but relatively weak upper level low is
centered across the northern Gulf Coast this morning while
Hurricane Maria continues to move to the north well east of the
Bahamas. The upper level low is forecast to meander a little west
today, while Maria continues it`s trek to the north with no threat
to Florida. Special 06Z MFL sounding shows PWATs remaining on the
high side of normal around 1.9" with seasonable midlevel temps
around -6C. However analysis shows a little drier air, the result
of subsidence around Maria, just to our east that will advect
across the region later today.

It looks like ongoing isolated activity over the Atlantic/east coast
will continue through the morning hours, becoming more scattered
over the interior later this afternoon. Best coverage will generally
be just inland from the Gulf coast where the diffuse east coast
breeze will collide with the Gulf breeze. Overall coverage, as well
as the heavy rain threat will be less than yesterday as instability
and moisture will be lower. Showers and storms diminish over land
after sunset, with isolated activity over the waters tonight.

UPCOMING WEEK: Hurricane Maria will continue moving northwards,
paralleling the US east coast into midweek. Midlevel flow will
become more westerly across the region as the hurricane moves north
of the region on Monday. The mid-upper level low that is currently
meandering around the northern Gulf coast is forecast to be absorbed
into the larger circulation around the storm by midweek, leading to
a trailing trough across the Florida peninsula.

Models now show this trailing trough digging back across the
southeastern Gulf mid-late week, with flow backing southwesterly a
little earlier on Wednesday Night. It looks like a pretty sharp
moisture gradient will setup over South Florida, with a very dry
airmass from Lake Okeechobee northwards and higher moisture
lingering across extreme southern Florida.

Tuesday and Wednesday are trending towards the driest days of the
week with little, if any, precip north of the I-75 corridor and
only isolated chances further south. More scattered pops are
expected across the area to round out the end of the week.

MARINE...The main marine concern through the upcoming week will be
a reinforcement of long period northeasterly swell in the local
Atlantic waters. As Hurricane Maria lifts north of the Bahamian
Islands later today, models show a continuing increase in seas,
building up to 8ft off the Palm Beach County coast by this
evening and potentially higher into Monday and Tuesday. This will
be with swells reaching 4-7ft at 12-13 seconds. Seas are expected
to peak at 5-7ft for the Broward and Miami-Dade waters on Monday
and Tuesday.

Based on these trends a Small Craft Advisory remains in place for
the Palm Beach County waters through Monday afternoon, though it may
need to be extended in time as swell continues into midweek. For now
it doesn`t look like it will need to be extended further south.

Gulf waters remain 2ft or less through the week. Light
northeasterly winds for all the waters today become more north-
northwest for Monday and Tuesday, then westerly into midweek.

BEACH FORECAST...Increasing northeasterly swells will result in
strong rip currents along all the Atlantic beaches through much of
the upcoming week. A High Risk for Rip Currents remains in effect
for Palm Beach County today, which will likely have to be extended
further south into Broward and potentially Miami-Dade later this
afternoon as the higher swells arrive.

With the northeast swell forecast to build to 5 to 7 feet with
periods 12-13sec, there will be the potential for breakers reaching
8-10ft in Palm Beach County. Current timing has the largest swell
arriving towards daybreak Monday, so have held off on issuing a
High Surf Advisory. With the recent passage of Irma, many
beaches have already seen considerable beach erosion, so more
impacts may been seen even at lower breaker heights.

&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  88  76  92  76 /  30  10  10  10
Fort Lauderdale  89  79  92  77 /  30  10  20  20
Miami            90  78  93  77 /  40  20  30  20
Naples           90  76  89  77 /  40  30  10  10

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through this evening for FLZ168.

AM...Small Craft Advisory until 5 PM EDT Monday for AMZ650-670.

GM...None.

&&

AVIATION...02/RAG



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