Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 192000
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
400 PM EDT Mon Aug 19 2019

.DISCUSSION...
Main weather story for the next day or so will be a surface trough
currently spread across the Bahamas near 77W/78W and its gradually
migration towards the Florida peninsula overnight tonight and into
Tuesday as the western Atlantic ridge axis lifts northward. What
does this mean? Well, a trend of higher coverage in showers and
storms will be expected tomorrow and this is due to a few
reasons...

1. The Saharan dust will slowly lift northwestward and models have
it completely out of South Florida by Tuesday. This will allow a
re-moistening of the local airmass with PW`s creeping in excess of
2.00 inches. Portions of the west coast Tuesday have values
exceeding 2.50 inches, so heavier coverage is expected there,
especially during the afternoon through early evening hours.

2. The aforementioned moistening will be brought upon by the
second factor, the combination of a westward moving surface trough
stated above that will pass to our south tonight with it`s
northern end moving into South Florida by Tuesday morning. These
features have a midlevel reflection that will erode the western
end of the ridge, bringing in a little cooler temperatures aloft.
GFS guidance suggests that 500 mb temps will cool to -7 to -8 C
Tuesday, so stronger updrafts and potentially stronger storms will
definitely not be out of the question.

With that said, the highest rain chances of the week will likely
be Tuesday as the influence of the above factors are maximized. We
will still see a diurnal maximum of activity in the afternoon
with daytime heating (although heating will be slightly deterred
due to higher cloud coverage) and diffuse east coast seabreeze.
While the highest coverage will be across inland SW Florida and
the Gulf coast, locally heavy rain may be a concern for all
locations. Periodic gusty winds are not out of the question
either.

For the latter half of the week, perturbations of the western
Atlantic ridge will be the largest influence on the weather across
South Florida. The axis of the ridge will generally be to our
north, putting us in prevailing deep east/southeast flow, so
plenty of moisture will stick around with a more seasonable
coverage of scattered showers and thunderstorms once the trough
passes to the west. PW`s look to drop into the 1.65 to 1.90 inch
range with the exception of Friday where values drop to around
1.50 inches. As we end the week, the western Atlantic ridge looks
to weaken, however, it will still exert enough influence to keep
us in prevailing easterly flow. This will continue to push the
highest coverage towards the Gulf coast and inland SW Florida each
afternoon. Convection will generally be diurnally driven,
developing along the seabreezes in the late morning and
afternoons.

Quick side note about a brief return of Saharan Dust -- models
are hinting that minute amounts of Saharan dust (around 20 to 40
micrograms per cubic meter) return to South Florida Wednesday and
Thursday but will quickly dissipate.

For the upcoming weekend, a tropical wave currently located around
38W looks to enter the forecast picture. Models have this feature
tracking a little further north and east of the area, so deep
moisture looks to be the main impact, and thus, higher rain and
storm chances this weekend. Exactly when, what, and where it
arrives will determine when enhanced rain chances may return to
South Florida. For now though, scattered to locally numerous
showers and storms will be the forecast for the upcoming weekend
into early next week.

&&

.MARINE...
Prevailing east/southeast winds will be in place for most of the
upcoming week with the Atlantic ridge axis to the north of the
region. Speeds will generally be 10 kt or less across the Gulf
waters and Lake Okeechobee with 10-15 kt winds across the Atlantic
waters. The main boating concern will be showers and storms
across the local waters each day. Prevailing flow will lead to
more storms pushing off the Gulf coast in the afternoons and
evenings. Expect locally higher winds and waves near any
convection.

&&

.AVIATION...
Showers and isolated thunderstorms should cause sub-VFR dips in
ceilings and visibilities across the eastern terminals early this
afternoon before the greater coverage of showers/storms shifts
towards the interior and Gulf coast areas this evening.
Prevailing easterly winds should continue, becoming light and
variable tonight for inland locations. Shower chances (with
occasional thunder) should return late tonight for the eastern TAF
sites and continue into Tuesday for most areas.

&&

.BEACH FORECAST...
A return in east/southeast wind flow will gradually increase the
Rip Current risk for Atlantic beaches throughout the next couple
of days.

&&

.HYDROLOGY...
A lack of widespread coverage the last couple of days has allowed
the ground to tolerate heavy rainfall a bit better. Locally heavy
rainfall anywhere in South Florida could still cause minor flooding
over the coming days but the prevailing flow will tend to
concentrate afternoon showers and storms towards Gulf coast and
SW Florida.

Fisheating Creek at Palmdale continues to slowly rise and is
currently at 6.41 feet as of 3 PM EDT. The forecast trend is an
expectation for Fisheating Creek to gradually rise over the coming
days as additional rainfall falls across the basin. At this time,
the forecast remains for the creek to stay below flood stage at
Palmdale.

&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  79  89  78  90 /  30  40  30  40
Fort Lauderdale  80  88  78  89 /  30  40  40  50
Miami            79  88  78  90 /  30  50  30  50
Naples           77  90  75  89 /  30  60  60  60

&&

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


DISCUSSION...03/Fell & 18/Weinman
MARINE...03/Fell & 18/Weinman
AVIATION...34/SPM
BEACH FORECAST...03/Fell & 18/Weinman
HYDROLOGY...03/Fell & 18/Weinman



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