Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 241643
AFDMFL

Area Forecast Discussion
National Weather Service Miami FL
1243 PM EDT SUN JUL 24 2016

.UPDATE...
Updated zone forecast and grids for the rest of this afternoon as
the Atlantic coastal metro areas may also experience increased
chances for thunderstorms. Some storms may become strong and
capable of producing small hail, strong gusty winds and localized
flooding.

Stay tuned to our NOAA weather radio, your local media outlets and
our website weather.gov/miami for the latest weather information
from your National Weather Service Office in Miami.

&&

.PREV DISCUSSION... /issued 940 AM EDT SUN JUL 24 2016/

UPDATE...
Looking at the situation for today, an upper level low is
currently positioning itself over the CWA, currently near Palm
Beach county. This mornings sounding showing the 500mb temps have
dropped to -8.7C and the freezing level is down to 14.4k ft. PWATs
are up to over 2 inches once again, and the water vapor imagery is
showing some drier air aloft moving into the area. Although the
sounding is fairly moist, the cooler air aloft, and any dry air
intrusion aloft, may allow for some small to moderate sized hail
to develop. The sounding is showing surface based CAPE at already
2345 J/kg this morning, and the modification of the sounding
shows that CAPE could be over 3600 J/kg. Also, after modifying
this mornings sounding to expected afternoon conditions, the NCAPe
(normalized CAPE) is coming in at .3. This would indicate some
strong vertical velocities with the thunderstorms this afternoon.
This would also support some hail development. Another concern is
the slow movement of the showers and storms this afternoon. With
the low over the area, and storm movement nearly stationary, urban
street flooding may once again be possible. Shear is still fairly
weak, but waterspouts will still be possible with any convective
cells over all South Florida waters through the day.

Looking at the HRRR, it has a modest handle on the situation this
morning, with cells over the coastal waters. It does show the
convection should hold off over the mainland until early this
afternoon. So, have lowered PoPs over the interior areas for this
morning, but kept likely this afternoon.

PREV DISCUSSION... /issued 754 AM EDT SUN JUL 24 2016/

AVIATION...
Another busy day is in store for South Florida, with mainly
afternoon showers and thunderstorms developing over the Atlantic
coast, then slowly migrating inland. After yesterday, which today
should have some similarities, have placed a prevailing SHRA at
the east coast TAF sites, with a VCTS after 17z. The activity
should move far enough west by around 22z, that dropped
precipitation down to a VCSH for now. Otherwise, VFR conditions
through the TAF period, with some IFR possible under heavy showers
and storms.

PREV DISCUSSION... /issued 554 AM EDT SUN JUL 24 2016/

UPDATE...
As of 555 AM EDT...Quick update to the forecast to account for
clearing skies across Hendry, Glades, Palm Beach, and Broward
counties and to bump up Pops over the Gulf local waters, as
persistent stratiform rain shield with embedded thunder will
continue through daybreak. Rest of forecast remains on track with
only minor updates to account for the latest observations.

PREV DISCUSSION... /issued 346 AM EDT SUN JUL 24 2016/

DISCUSSION...

SYNOPSIS...

High pressure across the southeast United States and a
south/southeast flow will prevail over South Florida over the next
several days. Aloft, an upper-level low will track across the region
Sunday, with upper-level ridging returning for next week. A tropical
wave will continue moving westward towards the Yucatan, while
another tropical wave moves across the central Atlantic.

NEAR TERM /THROUGH 6PM SUNDAY EVENING/...

Scattered to numerous thunderstorms expected across much of South
Florida today, some potentially strong...

As of 345 AM EDT...A cluster of showers and thunderstorms
continues to be ongoing over the Gulf waters and coastal Collier
County early this morning, as a weak upper-level low is situated
off the South Florida Atlantic coast. These thunderstorms have
exhibited frequent lightning and heavy rain, with radar estimates
indicating up to 3 inches in spots. The upper-level low will
slowly drift southwest, over South Florida during the day today,
bringing with it cooler 500 hPa temps around -8 C, below normal
for late July, later this morning into the afternoon hours.

With the upper low nearby, along with sea breeze/outflow boundary
convergence, expect another active day of showers and
thunderstorms especially this afternoon and evening. Model
guidance is suggesting that the greatest coverage will be across
the interior north into the Lake Okeechobee region, extending east
into inland Palm Beach and Broward counties, with more scattered
activity during the late morning/early afternoon hours along the
Atlantic and Gulf sea breezes. Both the Atlantic and Gulf sea
breezes are not expected to be particularly strong, so the
placement of outflow boundaries will be key to where convection
ultimately focuses.

Some storms today could be locally strong to perhaps severe, with
frequent to excessive lightning, gusty winds 40-55 mph, and small
hail, although a storm or two may be able to produce hail
approaching severe limits. Waterspouts will also be possible over
the nearshore waters. Heavy rainfall will also be a threat with slow
moving thunderstorm clusters, with poor drainage and urban flooding
possible.

High temperatures will generally range from the upper 80s to lower
90s, with a few mid 90 readings possible in the interior where
convection holds off the longest. Heat index readings will generally
be in the 90s.

SHORT TERM /6 PM SUNDAY EVENING THROUGH MONDAY NIGHT/...

With the upper-level low lingering near South Florida, showers and
thunderstorms may last well into the night with the primary threat
being frequent lightning, as the loss of daytime heating will limit
hail and wind potential. Locally heavy rainfall will continue to be
a threat as well, with poor drainage flooding possible. Convective
coverage should begin to wane after midnight. Low temperatures will
generally be in the 70s.

The flow will shift slightly more to the southeast on Monday and be
a little stronger than recent days, with additional scattered to
numerous showers and thunderstorms mainly during the afternoon and
evening hours primarily over the interior and Gulf Coast. Midlevel
temperatures will warm back to seasonable levels, helping to reduce
the threat of strong storms with frequent lightning and heavy
rainfall the primary threats. Convective activity will begin to wane
during the evening hours as drier air begins to work into the
region. High temperatures will be slightly warmer on Monday, in the
lower to mid 90s except for upper 80s along the immediate Atlantic
coast. Low temperatures Monday night will range from the mid 70s to
near 80.

LONG TERM /TUESDAY THROUGH SATURDAY/...

The long term period will feature mainly afternoon and evening
scattered showers and thunderstorms, with a continued easterly flow
keeping the bulk of the activity across the interior and Gulf Coast.

Model guidance and latest observed satellite analysis continue to
depict a potential intrusion of Saharan dust into the western
Atlantic, extending into South Florida beginning as early as Tuesday
and continuing through much of the work week. Despite this possible
dry air intrusion, a tropical wave approaching the eastern Carribean
and a slight weakening of the upper-level ridge may still allow for
scattered showers and thunderstorms. Will favor the drier end of
guidance at this time, but still keep a scattered threat and
continue to monitor.

Temperatures will be near normal for late July during the long term
period.

MARINE...

A light east/southeasterly flow will prevail across the local
Atlantic and Gulf waters today, generally around 10 knots or less.
Locally higher winds will be possible in and around thunderstorms,
along with frequent lightning and rough seas. Seas are expected to
be 3 feet or less with little to no swell. The east/southeasterly
flow will begin to increase heading into next week, with minor
increases in seas possible.

Rip current risk will be low today for Atlantic and Gulf beaches,
but may increase by the midweek period with increasing
east/southeast onshore flow for Atlantic beaches.

&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  77  91  79  92 /  20  50  20  20
Fort Lauderdale  78  90  80  91 /  20  50  20  20
Miami            76  91  80  91 /  20  50  20  20
Naples           74  90  77  92 /  30  50  30  30

&&

.MFL Watches/Warnings/Advisories...
FL...None.
AM...None.
GM...None.
&&

$$

UPDATE...17/AR



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