Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 221406
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
1006 AM EDT Sun Apr 22 2018

.UPDATE...
No changes needed to be made to the previous forecast as
everything looks on track. Scattered showers and thunderstorms
will continue to develop across the region today. The best chance
of thunderstorms will shift from the east coast metro areas to the
western interior sections this afternoon in the predominant
Southeasterly flow. The greatest threats with these storms will be
lightning, locally heavy downpours and brief gusty winds.
Scattered showers and thunderstorms will continue through tonight
especially across the east coast metro areas.

&&

.PREV DISCUSSION... /issued 730 AM EDT Sun Apr 22 2018/

AVIATION...
Scattered showers and thunderstorms across South Florida today
will create brief times of sub VFR conditions. Easterly flow will
start to veer more to the southeast today. At KAPF, a Gulf sea
breeze will develop this afternoon. Winds will be between 10 and
15 knots, however, they could gust higher in showers and
thunderstorms.

PREV DISCUSSION... /issued 333 AM EDT Sun Apr 22 2018/

DISCUSSION...
A relatively active pattern is now in place. A vertically-stacked
upper low is over the Southern Plains early this morning, with
our region in a downstream area of upper diffluence. At the
surface, high pressure over the Tidewater region and a low over
the Ozarks is yielding moderate southeast flow over South Florida.
This has also established a modest feed of tropical moisture with
PW values near or over 1.5 inches per the Nassau 00Z sounding and
GOES-16 Total PW imagery. Scattered showers and isolated
thunderstorms over the Atlantic waters have been moving inland
over the east coast metro area early this morning.

Today and tonight, scattered to occasionally numerous showers and
isolated thunderstorms will continue along the moisture axis from
the Atlantic into the east coast. During the afternoon, the best
chances for numerous showers and a few thunderstorms will focus
over the western interior and Lake Okeechobee region in the
predominant SE flow. The lowest POPs will be in the far southern
Peninsula bordering Florida Bay.

Monday, flow veers a bit to SSE, becoming SSW over western
sections later as a surface front approaches. This will favor
numerous showers and a few thunderstorms over the Lake Okechobee
region shifting toward the Palm Beaches Monday night as flow veers
around to SSW, with scattered to sometimes numerous showers
elsewhere.

The greatest threats associated with convection today through
Monday night are likely to be lightning, brief gusty winds, and
locally heavy downpours. Most areas north of an Immokalee to
Hollywood line will likely end up with a general 1-2 inches of
rain, but some isolated amounts over 3-4 inches will be possible
just about anywhere, which may bring brief periods of flooding to
streets and the usual vulnerable locations. Right now expecting
any flood issues to remain local and mostly advisory-level.

Tuesday into Tuesday night, the low kicks out into the Tennessee
Valley, pushing a surface front across the northeastern Gulf
toward the area. Models indicate CAPE increasing into the
2500-3000 J/Kg range, confluent southerly flow, bulk shear of
30-40 knots in the lowest 6km, differential CVA increasing with
height, and some modestly cool air aloft, all arguing a few
thunderstorms Tuesday may be strong. Greatest coverage over the
northern part of the area closest to the front, with more
scattered activity further south. Lack of any low-level jet and
increasing detachment of the front from the better upper forcing
lifting away from the region will serve as mitigating factors for
any widespread severe thunderstorms.

Wednesday, the decaying front pushes out of the area bringing
drier air into the region and bringing calmer weather. Later in
the week into next weekend, several disturbances translate
southeastward around the back of the eastern US mean longwave
trough. This will drive a couple of reinforcing fronts toward the
region. Will not get fancy with the POPs as the timing of these
fronts and quality of moisture availability will likely change
with future model runs.

MARINE...
Moderate to fresh southeast winds continue over the local waters
today. The winds and waves likely peaked out early this morning
over the Gulf Stream, so for now the Small Craft Advisory will be
allowed to expire later this morning. Still, small craft should
exercise caution through Tuesday, particularly over the open
Atlantic waters, due to winds of 15 to 20 knots. Scattered
thunderstorms will also pose a hazard to mariners in all the local
waters, bringing locally higher winds and waves through Tuesday
night. As a front approaches, winds will veer around to southeast
later today, southwest by Tuesday, and then around to northwest
Tuesday night following its passage.

AVIATION...
Passing showers, and possibly thunderstorms, through the forecast
period will create brief bouts of sub-VFR conditions. Generally
easterly flow will veer a bit more south of east today. APF will
see the influence of a Gulf sea breeze today as well. Variable
gustiness possible around convection today.

BEACH FORECAST...
A high risk of rip currents will continue today at the Palm Beaches
due to persistent moderate southeasterly winds, with a moderate risk
at the rest of the Atlantic beaches. At least a moderate risk will
continue for east coast beaches Monday.
&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  82  72  83  71 /  60  60  50  60
Fort Lauderdale  82  74  83  73 /  40  50  50  40
Miami            85  73  86  73 /  40  40  40  40
Naples           85  70  85  71 /  30  30  30  30

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk until 8 PM EDT this evening for FLZ168.

AM...Small Craft Advisory until 11 AM EDT this morning for AMZ650-651-
     670-671.

GM...None.
&&

UPDATE...55/CWC









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