Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 240112

Area Forecast Discussion
National Weather Service Miami FL
912 PM EDT Mon Oct 23 2017

Showers have been somewhat slow to develop so far this evening,
but the 00Z MFL sounding confirms satellite indications of
increasing moisture throughout the troposphere, with precipitable
water now up to 1.8 inches. The 00Z KEY and TBW soundings indicate
a PW plume of 2.0 to 2.2 inches is moving into the western part
of South Florida this evening as a long-anticipated front
approaches the region. Lowered POPs for a few hours across much of
South Florida this evening and early tonight, but a steady upward
trend in shower activity is expected overnight, particularly from
west of Lake Okeechobee southward toward the southwest coast and
adjacent Gulf waters.

Tuesday still looks like a cloudy day with scattered to numerous
showers and a few thunderstorms as the front slowly approaches the
region. No changes were needed to the forecast.


.PREV DISCUSSION... /issued 745 PM EDT Mon Oct 23 2017/

Scattered SHRA expected to develop overnight across the area as a
front approaches. Best chance of showers late tonight from Lake
Okeechobee toward the Gulf coast of SW Florida, so PROB30 SHRA
with MVFR restrictions mentioned at KAPF. Otherwise VFR
prevailing, but with gradually lowering cloud bases. Cannot rule
out an isolated TSRA or two anywhere across S FL but chances too
low to mention at this time in the TAFs. Winds becoming light
overnight before southerly winds pick up after sunrise.

PREV DISCUSSION... /issued 421 PM EDT Mon Oct 23 2017/

An approaching cold front will bring an increase in chances for
showers and thunderstorms for tonight, through Wednesday night.
The current forecast calls for the front to pass through South
Florida Tuesday night, into early Wednesday morning. Given the
front will not be totally clear of the area lows Wednesday are not
forecast to drop lower than the low 50`s in the western Lake
region. As the front exits the area Wednesday, cooler air should
be advected into the region. Highs in some areas of the interior
may struggle to reach 70 on Wednesday.

By Wednesday night, the front should be well away from the region.
This would normally allow for radiational cooling to bring the
coolest temperatures after a front. However, models are
indicating the wind will not decouple and remain northwest at 8
to 12 kts. This would keep the atmosphere mixed, and thus, the
cooler air would only be that which is advected in, not due to
radiational cooling. Even so, temperatures west of the Lake are
forecast to drop into the low 50`s Thursday morning, mid 50`s
along the Gulf coast, upper 50`s in the western metro area of the
Atlantic coast, and low 60`s along the Atlantic beaches.

The weather is forecast to be quiet through the end of the week as
high pressure builds over the southeastern US.

By Saturday, and area of tropical moisture, as well as a weak low,
will move up from the south. This will help to increase chances of
convection once again for Saturday and possibly Saturday night.
Both the GFS and the ECMWF have a weak low moving northeast over
central Cuba, and then progressing over the Bahamas by Sunday
night. This is ahead of the next cold front, which models area
showing to push through by next Monday morning.

Conditions are forecast to deteriorate overnight and into
tomorrow, as a cold front pushes through the area. This will first
bring an increase in the chances for showers and thunderstorms.
Then the wind will increase to 15 to 20 kts immediately behind
the front early Wednesday morning and to around 20 kts over the
gulf waters. This is forecast to bring building seas, with the
Gulf building to 7 to 9 feet by Wednesday afternoon. For the
Atlantic seas are forecast to build to around 7 feet by Wednesday
night. Conditions are forecast to begin to improve for the Gulf
Thursday morning, and Friday morning for the Atlantic.

West Palm Beach  75  85  68  73 /  40  70  70  50
Fort Lauderdale  77  85  70  75 /  40  60  70  50
Miami            77  85  70  74 /  40  60  70  50
Naples           73  83  67  75 /  40  60  30  10



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