Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 230011

Area Forecast Discussion
National Weather Service Miami FL
811 PM EDT Mon May 22 2017

.UPDATE...The last few visible satellite images this evening show
very well the story of the afternoon. Skies remain nearly clear
along both coast, with a line of storms stretching from the west
side of Lake Okeechobee through Hendry and Central/East Collier
counties where the seabreezes have collided. Coverage and
intensity is already on the downswing, and expect convection to
generally diminish by 10-11pm tonight. A few outflow boundaries
may kick off a shower or two through this evening along the
Collier coast. Otherwise, once convection diminishes expect
another muggy night under partly cloudy skies.


.AVIATION...TSRA will linger over western interior through 23/02Z,
but likely will remain away from any terminals. Will keep VCSH
mention at KAPF through this time for some of the towering Cu
currently visible on satellite. Light S or SSE flow at all sites
after 04Z, increasing to 10-12kts after 14Z. Seabreezes should
reach all sites tomorrow, though KPBI-KTMB-KOPF will be later,
16Z-17Z and KAPF may not become WSW until 19Z. For now, TSRA
development looks to remain inland of all sites and have kept it
out of the TAFs.


.PREV DISCUSSION... /issued 348 PM EDT Mon May 22 2017/

..Marginal to Slight Risk of Severe Weather Wednesday through


TONIGHT THROUGH TUESDAY...High pressure over the western Atlantic
waters will move east through Tuesday allowing for a cold front
over the Tennessee Valley to move into the Southeastern United
States. This will allow for the steering flow over South Florida
to swing to more of a southerly direction on Tuesday. The east and
west coast sea breezes will also develop each day and push
inland. Therefore...the best chance of showers and thunderstorms
this afternoon and again on Tuesday afternoon will be over the
western interior areas of South Florida with emphasis shifting to
the eastern interior areas on Tuesday as steering flow veers.

WEDNESDAY THROUGH THURSDAY... A trough of low pressure across the
rockies will move southeast and amplify as it moves into the
Tennessee Valley by middle of this week. This in turn will allow for
the front over the Southeastern United States to move southward into
northern Florida, and allow for the steering flow over South Florida
to be south/southwest bringing in deep tropical moisture to the
area. Therefore, numerous showers and scattered thunderstorms should
develop over South Florida Wednesday though Thursday with the
consensus of the models signaling front passing by to our north or
dissipating across the region by late Thursday.

A mid to upper level jet 100 to 130 knots will be moving around the
base of the trough through Georgia/Northern/Central Florida middle
of this week or around wednesday night into the early half of
Thursday, as a low level jet of 50 knots will be moving through
north and central Florida during the same period. Only model
bringing low level Jet of 50+ knots as far south as the Lake Okee
region is the NAM as this time. This all means increasing chances of
rain Wednesday through Thursday. There is certainly a potential for
a few strong or even severe thunderstorms. The question is when. One
possibility is ahead of the trough on wednesday afternoon where we
will likely be exposed to good daytime heating and may be slightly
steeper low/mid level lapse rates than normal. Overnight is when the
best upper level dynamics will be passing by to the north but it
does not stretch far enough south to make up for weakening low level
frontogenetical forcing and lack of heating even into Thursday when
it will be cloudy and wet. Certainly there is a marginal to slight
slight risk of severe weather at best but it is not a slam dunk at
this time. Will continue to monitor as the next two days progress.

The primary potential impacts at this time are a few strong storms
Wednesday afternoon with may be some small hail and strong winds and
again showers and storms with wind gusts in excess of 40-50 mph
overnight wednesday into the early part of thursday. One or two
tornadoes cannot be ruled particularly late Wednesday and wednesday
night when NAM shows 0-1 km helicities in the 200-300 range across
southwest Florida coast and the Lake Okeechobee region. But again
that is against limiting factors mentioned earlier.

EXTENDED FORECAST...THROUGH MONDAY...The trough of low pressure will
continue to move east into the western Atlantic waters late this
week into this weekend, as low level high pressure ridge builds back
across the region. Typical summertime like pattern should be
settling across the area with sea breezes developing and pushing
inland each day with isolated to scattered showers and thunderstorms
developing each afternoon with the best coverage over the interior

MARINE... Increasing winds of 15 to 20 knots generally from the SSW
and then WSW Wednesday through early part of Thursday will result in
small craft exercise caution conditions across much of the local
South Florida waters if not periods of small craft advisory
conditions. Boating conditions will improve once again late this
week outside local thunderstorms which will increase wednesday and
thursday in coverage as well.

West Palm Beach  76  91  75  90 /  10  30  20  50
Fort Lauderdale  77  89  78  90 /  10  20  20  40
Miami            76  89  78  91 /  10  10  20  50
Naples           74  89  77  87 /  10  20  20  50



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