Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 230531 AAB
AFDMFL

Area Forecast Discussion...UPDATED
National Weather Service Miami FL
131 AM EDT Sat Sep 23 2017

.AVIATION...
The winds will remain northeast at 5 to 10 knots today at all taf
sites, except for KAPF taf site where they will become westerly
after 18Z. Showers will develop today over all of the taf sites
with even some thunderstorms over the east coast areas between
15Z and 18Z. KAPF taf site should see some thunderstorms between
18Z and 24Z. Therefore, a PROB30 group has been added for all taf
sites for the thunder threat. The ceiling and vis should remain in
VFR conditions, but should fall down into MVFR conditions with the
thunderstorms.

&&
AVIATION...54/BNB


.PREV DISCUSSION... /issued 727 PM EDT Fri Sep 22 2017/

AVIATION...
Scattered SHRA/isolated TSRA expected to affect east coast sites
through about 04z, along with MVFR and brief IFR conditions as moist
NE flow continues across region. After temporary break late tonight,
another round of SHRA/TSRA with similar conditions from 09z-18z
Saturday covered by PROB30 in forecast. At Naples/KAPF, ongoing
SHRA/TSRA will dissipate by 02z with mainly dry weather until 18z
Saturday when scattered TSRA/PROB30 return to area. Mainly NE
surface winds, gusty in and near SHRA/TSRA.

UPDATE...
Convection is ongoing this evening. The gulf coast will be winding
down over the next hour or two, while the Atlantic coast sees an
increase in activity for a few hours. By late this evening, most
of the activity should trend to offshore, over the Atlantic
waters. However, this activity may also move onshore. The onshore
flow, a weakening ridge aloft, and somewhat increase in
instability, being slightly influenced by Maria, mainly breaking
down the 500mb ridge as it moves north, remaining well to the
east, may cause some increased activity in the pre-dawn hours as
well.

&&


PREV DISCUSSION... /issued 337 PM EDT Fri Sep 22 2017/

DISCUSSION...
A large ridge over the eastern US and Hurricane Maria staying well
east, is forecast to keep the flow across the region on the light
side. This will allow the pattern to be mainly sea breeze
dominated through the weekend, with a tendency to drift to the
southwest as they have been doing the last couple of days. PWATs
look to stay near 2.25 inches over South Florida through the
weekend. This will bring heavy rain will any convective showers or
storms through the afternoon hours. With drainage difficulties
from sewers with debris still around from Irma, this could lead to
some urban type street flooding, especially along the east coast
metro areas.

By Monday, Maria should be far enough to the northeast that the
area sees some drier air pulled in. This would reduce the
convective activity after the weekend significantly. Pwats drop
off a little each day, with values around 2 inches on Monday, and
nearing 1.5 inches by Wednesday over much of the area. This would
support the model decreasing convection through the week, next
week.

MARINE...
Seas will build over the next several days as Hurricane Maria
moves well to the northeast of the area. Maria is forecast to
bring increasing swell to the area, with a 5 to 6 foot long period
swell to areas along the Atlantic coast, especially the Palm
Beach County area. The period is currently forecast to be 12 to 13
seconds. This swell may cause high surf for Palm Beach County
coastal areas, and possibly further south, as early Sunday
afternoon.

By Saturday afternoon, seas are forecast to build to 5 to 6 feet
across much of the South Florida Atlantic waters, and exceeding 7
feet by Sunday morning. This will cause hazardous marine
conditions for small craft by the later half of the weekend,
which may persist through much of next week.

BEACH FORECAST...
With a northeast swell forecast to build to 5 to 6 feet,
especially off Palm Beach County, high surf is a significant
possibility. It has already been causing strong rip currents in
this area, and will likely continue to through much of next week.
It is also possible that coastal areas further south, may be also
see a high risk of rip currents after tomorrow morning. Also, with
over a 5 foot swell, it is possible for coastal areas to see 10
foot breakers by late this weekend, into the beginning of next
week. This may necessitate an advisory in the next couple of days.
This may also bring a concern for beach erosion for portions of
the Atlantic coastline of South Florida.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  78  89  76  91 /  40  40  10  20
Fort Lauderdale  79  90  77  90 /  40  40  20  30
Miami            79  90  78  91 /  30  50  20  30
Naples           75  90  75  90 /  20  50  20  20

&&

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

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

UPDATE...13
DISCUSSION...13
MARINE...13
AVIATION...54/BNB
BEACH FORECAST...13



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