Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 230826 CCA

Area Forecast Discussion
National Weather Service Miami FL
403 AM EDT Wed Aug 23 2017

Latest IR satellite imagery shows convection bubbling over
Atlantic waters near the central Bahamas. This activity can be
attributed to the unstable airmass and high moisture content
associated with a tropical wave. Satellite derived PWAT displayed
an impressive 2.2"-2.3" across the entire CWA, indicating
atmosphere moisture levels well above normal for this time of
year. Through the remainder of this morning, as the tropical waves
edges closer to the Atlantic coast, shower coverage should begin
to slowly increase. Short range models, including the HRRR and Hi-
Res WRF prog most of the activity to develop over various portions
of the peninsula early this afternoon, with the help of diurnal
heating. Light easterly flow may concentrate the showers over the
interior and Gulf Coast regions. With abundant tropical moisture
in place, heavy rain is possible, which may lead to local ponding
of water on the streets or flooding of low lying areas with any
storms that train over the same area. Maximum temperatures may
struggle to reach 90 degrees along the east coast metro today, due
to the increase in moisture and cloud cover. Meanwhile, low 90s
are forecast along the Gulf Coast.

Tonight through Thursday: The tropical low located near the
southern tip of the peninsula will remain rather stagnant tonight
into Thursday. With various vorticity maxima rotating around this
low, sufficient lift and instability will help to generate
numerous showers and thunderstorms, especially along the east
coast metro region. As the low slowly drifts northward late
Thursday, flow will turn south southeast, further drawing in deep
tropical moisture northward over South Florida. GFS forecast PWAT
values rise to between 2.3" to 2.4" and relatively high rain
rates could lead to a more substantial flooding threat. This
threat will be analyzed later this morning or early afternoon to
see if a flood watch is necessary during this timeframe.

Friday to Sunday: Both the GFS and ECMWF move the aforementioned low
northeastward off central Florida`s Atlantic coast Friday into this
weekend. In response, flow over South Florida will turn
southwesterly. Deep moisture, along with southwesterly flow may
concentrate showers and storms along the eastern portion of the
peninsula including the east coast metro region. This would further
prolong the threat of heavy rain and elevated flooding potential,
due to previously saturated grounds.


A trough over the Bahamas will move west over South
Florida through Thursday. The feature will generate southeast
winds over the waters this afternoon generally from 10 to 15 KT.
As the through lifts north late Thursday into Friday, surface winds
will shift to the south, then to the southwest. Expect periodic
showers and thunderstorms through the period with seas generally
below 4 feet.


Some scattered showers have developed over the Atlantic waters
during the overnight hours and moved inland, with tempos for -ra
in place for MIA and TMB. Brief MVFR cigs/vis are possible with
the heavier showers. TS has not been an issue so far, but VCTS
will be introduced after 15Z at all terminals. Current light winds
increase again to near 10 knots out of the east late this morning
and afternoon.


West Palm Beach  89  78  89  76 /  70  60  80  70
Fort Lauderdale  89  79  88  76 /  70  70  80  70
Miami            89  78  89  77 /  70  70  80  70
Naples           92  77  89  79 /  70  50  70  50



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