Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 162356

Area Forecast Discussion
National Weather Service Miami FL
756 PM EDT Mon Jul 16 2018

Showers have ended for the evening and dry/VFR conditions should
prevail through midday Tuesday.  Thereafter, scattered showers and
isolated thunderstorms appear possible at eastern terminals, so have
introduced VCSH for now.  Light wind tonight, generally southerly at
5 to 10 KT by late Tuesday morning, then  SE at around 10 KT during
the afternoon (WSW at KAPF) as sea-breezes become dominant.


Showers and thunderstorms mostly dissipated by 715pm this evening.
However, kept slight chance PoPs through early part of evening due
to lingering boundaries, mainly over the eastern half of South
Florida. Can`t rule out isolated showers or a thunderstorm
through early evening over the interior or the eastern half of
South Florida. However, most of South Florida should remain dry
tonight. Otherwise, the forecast remains on track.


.PREV DISCUSSION... /issued 402 PM EDT Mon Jul 16 2018/

Today-tonight: Scattered to numerous thunderstorms this afternoon
will drift northward, so highest concentration of late
afternoon/early evening storms will be over the northern half of
South Florida. A few storms have been strong so far this
afternoon. The activity over land should wane during the evening

Tuesday through Thursday night and possibly lasting into
Saturday, we will see a large scale weather pattern that is
characterized by troughs of low pressure and stormy weather over
the southeastern U.S., northern Florida, and possibly as far south
as central Florida. However, a strengthening subtropical high
nosing its way into South Florida is likely to prevent the
enhanced storminess from reaching the southernmost portions of the
Florida Peninsula for much of the week. At the same time, dry
mid-level air from the Saharan Air Layer is likely to affect South
Florida beginning sometime around late Tuesday and lasting for
much of the remainder of the work week. Layered precipitable water
imagery from CIRA shows that the dry air is most pronounced at
the 500-700 mb level and is currently approaching the Bahamas from
the east-southeast. There will likely be some breaks in the SAL
this week, and there could be a point in time later in the week
when the trough moves a little farther south. But for now, expect
rain chances to be somewhat lower on Tuesday through Thursday
compared to Monday for much of South Florida. During this time,
PWATs will be much higher over northern Florida compared to South
FL due to the trough.

Low-mid level steering will be from the southwest much of the
week, so any mid-afternoon storms that form would move toward the
northeastern part of South FL for late afternoon.

Heat index values Tuesday and and Wednesday are forecast to be as
high as 104-106 for the western half of Collier County, Mainland
Monroe and inland Miami-Dade over the Everglades. Heat index
values are also forecast to reach 104-106 for portions of metro
Palm Beach County Tuesday and Wednesday.

Friday-Sunday forecast will depend on how much and how quickly
the ridge breaks down, if at all. There is still significant
uncertainty as to if and when the trough to our north will move
southward. The ridge could hold through day 7, which would keep us
in a similar weather pattern. However, as time goes on, from day 5
to day 7, it appears that the chance of the ridge breaking down
will gradually increase. This means that moisture and PoPs could
increase over the weekend.

The western Atlantic ridge will build westward through the
week, with the axis generally draped across South Florida and the
adjacent waters. Prevailing flow will remain southerly through
Tuesday, then southwesterly late week as a frontal boundary
drifts into the FL peninsula. The increasing pressure gradient
will bring speeds up to 10 knots over the Gulf and 10-15 knots
over the Atlantic, still light enough to allow both the Gulf and
Atlantic seabreezes to develop each afternoon. Seas generally 2 ft
or less, occasionally 3 feet in the Atlantic.

Showers and storms will be a concern for all the waters through the
period, though coverage should generally be below normal. Locally
higher winds and seas are possible near any storms.


West Palm Beach  77  92  77  93 /  20  50  30  30
Fort Lauderdale  79  92  80  92 /  10  30  20  30
Miami            78  92  79  92 /  20  30  10  30
Naples           77  92  77  92 /  10  20  10  20



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