Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 200811

Area Forecast Discussion
National Weather Service Miami FL
311 AM EST Mon Nov 20 2017

Synopsis: An unsettled pattern setting up as a front stalls over
the region today and a series of disturbances moves over the
region Tuesday and again late in the week.

Near term (Today-Tonight): The front now moving through South
Florida will stall out later today near the southern tip of the
peninsula. Showers have been forming overnight over the Atlantic
waters along and behind the surface boundary, and the front will
continue to be a focus for showers today. As winds veer to more
easterly and the residual boundary begins to retreat northward,
the showers are likely to spread back over south Florida from
southeast to northwest this afternoon and tonight.

Short term (Tuesday-Wednesday): As the remnant front continues
moving northward Tuesday, the greatest concentration of showers
will also shift northward into the Lake Okeechobee/Palm Beach
region and up into central Florida. However, with a relatively
moist air mass in place and a shortwave trough approaching from
the Gulf, scattered showers will be possible at times farther
south Tuesday. The strengthening wind fields aloft and focused
upward motion ahead of the shortwave trough should be sufficient
for a few scattered thunderstorms Tuesday, particularly northern
sections closer to the front. Wednesday now appears to be a
relatively dry day with the remnant surface boundary north of the
area and lower tropospheric subsidence in the wake of the
departing shortwave trough.

Medium range (Thursday-Friday Night): Medium range models are
still having some difficulty with a complex mid troposphere
evolution expected. What they agree on is some vorticity dropping
into the Gulf Thursday, prompting cyclogenesis by Thursday morning
along the low level shear axis (remnant front). The timing of the
main shortwave trough turning the corner and lifting out is still
tricky, with the GFS now a bit faster than the ECMWF. So the
period from Thursday afternoon through early Friday will have the
highest chance for showers and scattered thunderstorms, but some
rain risk may stretch into late Friday if the slower ECMWF
solution is correct.

Weekend: Although there air mass behind the late week storm
system is not particularly cold, steadily drier air should invade
the region, bringing clearing skies Saturday and allowing low
temperatures to fall into the lower 50s northwest to lower 60s
southeast beaches Sunday morning.


Northerly wind surge behind the front is bringing 20-25 knot winds
to the Atlantic and Gulf waters early this morning. Winds on the
Gulf side will diminish this afternoon as the front washes out,
but the pressure gradient will remain tight over the Atlantic
waters through tonight as wind veer around to easterly, so
hazardous boating conditions will continue. The fresh breeze will
be accompanied by significant wave heights of 7 feet or so in the
Gulf Stream. Conditions improve Tuesday on through the rest of
the week, though scattered thunderstorms will be possible Tuesday
and again on Thursday into Friday.


There will be a moderate risk of rip currents at the Atlantic
Beaches today as onshore winds increase. If winds come around to
easterly and increase faster than currently forecast, a later
upgrade to high risk may become necessary. Regardless, beachgoers
should be aware of the risk of rip currents today.


.PREV DISCUSSION... /issued 120 AM EST Mon Nov 20 2017/

Cold front moving quietly through South Florida will bring little
wind change but increasing clouds. At Naples, MVFR CIGs will be
periodic through the overnight, and cant rule out that some of
this reaches KPBI, otherwise, VFR conditions should prevail.
Scattered showers should gradually spread westward into east coast
terminals midday, with activity persisting through the overnight.
North wind will increase a bit after daybreak, then expect NE wind
10-14 KT with gusts over 20 this afternoon.


West Palm Beach  79  72  81  67 /  30  60  50  20
Fort Lauderdale  79  73  83  69 /  40  60  40  20
Miami            80  72  84  69 /  40  60  40  20
Naples           83  67  83  66 /  30  20  60  20


AM...Small Craft Advisory until 7 AM EST Tuesday for AMZ650-651-670-

GM...Small Craft Advisory until 11 AM EST this morning for GMZ676.


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