Area Forecast Discussion
Issued by NWS Miami, FL

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FXUS62 KMFL 301411 AAA
AFDMFL

Area Forecast Discussion...UPDATED
National Weather Service Miami FL
1011 AM EDT Fri Jul 30 2021

.UPDATE...

KAMX radar and GOES-16 vis/IR imagery show lines of showers and
storms across Biscayne Bay and the nearshore Atlantic waters off
Broward and Miami-Dade counties thus far this AM. For the most
part this activity is remaining fairly benign outside of the
occasional wind gust and lightning. However, waterspouts are
possible today, especially with the lighter flow in place along
with somewhat healthy low-level lapse rates.

Fortunately, drier air has already filtered in portions of South
FL, noted by GOES-16 water vapor imagery, and this drier air
sifting around the base of high pressure over the Atlantic looks
to stick around through the remainder of the day. This should keep
convection that develops this afternoon less robust than previous
days. With that said, a stronger wind gust or two cannot be ruled
out, especially with multiple outflows and both sea breeze
boundaries expected during the afternoon hours when daytime
heating is greatest. The Gulf breeze is expected to progress
inland just fine, however the Atlantic breeze is somewhat
questionable -- some models suggest it pushing across interior
sections of the eastern counties and other models suggest pinning
the sea breeze along the coast. Depending on where the sea breeze
sets up will be a large contender on rain chances, rainfall, and
flooding this afternoon. Thus, capped PoPs at 50 percent for
today.

MFL`s 30/12Z sounding shows another day with very weak steering
flow and low-level winds. Models are all over the place with the
steering flow, though the majority suggest a SW flow whereas this
mornings sounding showed a SSE flow. Given the light nature of the
winds and the multiple boundaries expected, storm propagation
will be largely dependent on boundary collisions/motion. Localized
flooding will also be a concern with the slow storm motion,
especially in areas that received plenty of rain from prior days.
If the more westerly component of the steering flow were to be
dominant, the east coast may see convection once again during the
late afternoon/early evening hours. If the more easterly component
were to dominate, convection should stay mostly across interior
sections of South FL.

Highs today in the low to mid 90s, with heat indices in the triple
digits.

PREV DISCUSSION... (Issued 719 AM EDT Fri Jul 30 2021)

AVIATION(12Z TAFS)...
Generally VFR, though convection impacting a terminal could bring
bouts of sub-MVFR conditions. Light winds will give way to sea
breezes and outflows from convection. Short-fused AMDs may be
necessary through the period. Vicinity SHRA/TS this morning for
east coast sites before another round of convection forecast later
in the evening. Handled with PROB30s for the time being. For APF,
convection should mostly push inland, though handled with VCTS
for this afternoon. Drier conditions overnight.

PREV DISCUSSION... (Issued 356 AM EDT Fri Jul 30 2021)

Hot and stormy summer day across South Florida...

SHORT TERM (Today through Saturday)...
A surface ridge axis sits over southern Florida extending from high
pressure centered over the Atlantic. A diffuse remnant boundary
remains north of Lake Okeechobee which could help serve as a focus
for moisture. The pattern aloft is shifting with the trough
deamplifying into the Atlantic and the region sitting in the gap
between mid-level highs. Looking at the upper levels, another
tropical upper tropospheric trough (TUTT) is east of the Bahamas,
but this feature is not expected to impact our area in the short
term forecast period.

With the ridge axis situated over the region, light wind flow with
a southerly to south-southwesterly component is forecast. As such,
the diurnal sea/lake breeze circulations that develop and push
inland will have a large influence on the convective focus in the
afternoons and evenings. The light flow through the column
combined with healthy low-level lapse rates could lead to more
waterspout activity than in previous days as well. While
temperatures aloft remain fairly warm, some strong storms cannot
be ruled out today. Boundary collisions will be a driver for some
of these stronger storms which could bring strong wind gusts in
excess of 45 mph, torrential rainfall which could lead to
localized flooding, frequent to excessive lightning, and
potentially funnel clouds.

Temperatures will remain warm with highs reaching the low to mid
90s. Heat index values will reach into the lower to mid 100s.
Anyone partaking in outside activities should stay hydrated and
take cooling breaks over the next few days. If strenuous activity
can be rescheduled to cooler times of the day, that would also be
helpful to avoid heat illness.

LONG TERM (Saturday Night through Thursday)...
In the long term a cold frontal boundary and parent upper level
trough will move southward toward northern Florida before stalling
through a good portion of the upcoming week. Aloft, ridging will set
up across the Gulf of Mexico early in the period. This will help
warm the region, especially across the warmer interior. Rain chances
will be near climo levels this weekend. A lackluster low level flow
will allow for diurnal convection to develop along both the Gulf
Breeze and Atlantic sea breeze through early next week.

Eventually, the parent trough will come into play later in the
period as a series of weak impulses rotating around the basis of the
axis. This will flatten and eventually weaken the upper ridge across
the Gulf of Mexico while increasing rain chances by midweek as these
impulses interact with deep tropical moisture across our region.
With a stagnant typical summertime flow residing across our area,
hydro concerns may again increase toward the end of the period.

AVIATION(06Z TAFS)...
Generally VFR though convection impacting a terminal could bring
bouts of sub-MVFR conditions. Light wind flow will give way to sea
breezes and outflows from convection. Short-fused AMDs may be
necessary through the period. Convection overnight should remain
focused over the waters and transition ashore through the morning
and early afternoon hours before the focus shifts a bit more
inland.

MARINE...
Light wind and the lack of any major surface low pressure in the
region should keep seas 2 feet or less outside of locally higher
waves due to showers and thunderstorms through most of the week.
Waterspouts are also possible across all the South Florida waters
today, particularly the Atlantic coastal waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
Miami            79  92  79  93 /  20  40  20  50
West Kendall     78  94  77  93 /  10  30  20  50
Opa-Locka        79  94  78  93 /  20  40  20  50
Homestead        78  92  78  91 /  10  30  20  40
Fort Lauderdale  79  92  80  91 /  20  40  20  50
N Ft Lauderdale  79  92  80  92 /  20  40  20  50
Pembroke Pines   78  92  78  92 /  20  40  20  50
West Palm Beach  77  92  78  93 /  20  40  20  50
Boca Raton       79  93  78  93 /  20  40  20  40
Naples           78  92  78  92 /  20  30  10  40

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
GM...None.
&&

$$

Update/Aviation...Fell
Today through Saturday and Marine...RAG
Saturday Night through Thursday...Frye

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