Severe Thunderstorm Warning 70, NWS Miami, FL

Area Forecast Discussion
National Weather Service Miami FL
337 PM EDT Fri Aug 21 2026

...New UPDATE...

.KEY MESSAGES...
Updated at 335 PM EDT Fri Aug 21 2026

 - Heat index values peak between 105-110 degrees today with a
   Heat Advisory in effect only for Miami-Dade and Broward
   counties.

 - Scattered thunderstorms expected after midday and into the
   evening. A couple of stronger storms are possible that could
   produce near-severe winds.

&&

.UPDATE...
Issued at 335 PM EDT Fri Aug 21 2026

Water vapor satellite imagery shows a moister air mass continuing to
overspread South Florida today, with recent ACARS sounding data
showing PWATs around 1.9 inches. Isolated showers and thunderstorms
have begun forming this afternoon along the Atlantic sea breeze,
which has remained pinned close to the East Coast under persistent
southwesterly flow. High-resolution model guidance continues to show
increasing coverage of showers and thunderstorms across the eastern
half of South Florida and around Lake Okeechobee through the rest of
the afternoon into the early evening, with outflow boundaries
potentially driving some activity into SW Florida around sunset.
Primary threats include gusty winds, frequent lightning, and
localized heavy rainfall, though an isolated severe storm cannot be
completely ruled out. Convection is expected to gradually dissipate
following the loss of daytime heating after sunset. Overnight lows
tonight will range from the low 80s along the coasts to the mid 70s
inland.

&&

.SHORT TERM...
(Today through Saturday)
Issued at 116 AM EDT Fri Aug 21 2026

As the ridge in the Southwestern US continues to strengthen,
increased jet dynamics will result in an amplified trough across
most of the Eastern Seaboard through this weekend. The base of the
trough is not anticipated to make it all the way to South Florida
and the overall flow pattern will remain largely on the weaker side,
but this enhanced troughing pattern is expected to keep a prevailing
southerly/south-southwesterly flow pattern in place today and
Saturday. Therefore, with abundant moisture advection continuing and
elevated PWATs of 1.7-2.0" or even more in some areas, diurnal
heating and sea breeze circulations each day will have the necessary
ingredients to produce scattered to numerous showers and
thunderstorms. With the primary south to south-southwest flow, this
will favor interior and Southeast Florida for highest rain chances
both today and on Saturday as showers and storms are expected to be
the most widespread in these areas. Some activity will be observed
across Southwest Florida as well, just not as widespread and thus
rain chances are between 30-50% there versus 50-70% across Southeast
Florida. Model soundings do highlight adequate SBCAPE of 3000-4000
J/kg as well as inverted-V signatures and steep low level lapse
rates, so there will be an outside chance for an isolated severe
storm or two via gusty winds. Otherwise, the primary hazards will be
heavy rainfall that could lead to localized flooding in poor
drainage areas, and sub-severe strong wind gusts.

High temperatures the next couple days will remain in the low to mid
90s. The deeper moisture will also keep dew points in the mid to
upper 70s each day, thus maximum heat index values are anticipated
to remain elevated up to the 105-110F range. Isolated locations
could experience heat index values a couple of degrees higher for a
short period of time. With the expectation of some increased cloud
cover today and perhaps slightly lower dew points, it has been
decided to only issue a Heat Advisory for Miami-Dade and Broward
counties from 11AM - 6PM today. HREF probabilities currently
indicate a 10% or less chance for heat indices to reach 108F or
higher. Depending on how conditions are trending through the
morning, a short-fused expansion of the advisory will be possible
but is not imminent.

&&

.LONG TERM...
(Saturday night through Thursday)
Issued at 116 AM EDT Fri Aug 21 2026

As the trough draped across the Eastern Seaboard starts to erode
early next week, the local wind regime will start to shift back to
what we typically see in the summer time here in South Florida with
low level flow being dominated by the Atlantic sea breeze. This will
cause diurnal convection to start focusing back over both the
interior and Southwest Florida rather than Southeast Florida like
has been observed recently. Starting Monday, the highest rain
chances (60-80%) will begin to focus across Southwest Florida and
this will last through the end of the long term period.

Latest guidance shows some slightly drier air (PWATs falling back
below 1.8-2.0") this weekend, which could result in some slightly
lower dew points that end the current streak of consecutive days
with Heat Advisories. There is also potential for another Saharan
Air Layer (SAL) to impact the area late in the weekend and early
next week, but guidance highlights this SAL breaking up upon it's
arrival and thus it's influence on a return to hot conditions
should be less than the previous round.

High temperatures are projected to remain in the low to mid 90s each
day with overnight lows ranging from the low 70s across the interior
and lake regions to the upper 70s and low 80s along the coastal
metros.

&&

.AVIATION...
(18Z TAFS)
Issued at 127 PM EDT Fri Aug 21 2026

SHRA/TSRA will increase in areal coverage throughout the day with
the potential for sub-MVFR cigs/vis at some terminals in tandem with
erratic wind shifts. Onshore winds increase at all terminals this
afternoon, then return to light and variable after sunset. TEMPOs
and short-fused amendments may be needed with future TAF updates.

&&

.MARINE...
Issued at 116 AM EDT Fri Aug 21 2026

Gentle west-southwest winds are expected across the Gulf waters
today with southerly winds continuing across the Atlantic. The
Atlantic winds will eventually become more southeasterly over the
weekend. Seas will remain at 1-2 feet or less each day across all
local waters. Scattered showers and thunderstorms are possible late
each day and in the late night hours which may result in locally
hazardous winds and seas.

&&

.PRELIMINARY POINT TEMPS/POPS...
Miami            80  94  79  93 /  10  30  20  60
West Kendall     78  94  77  92 /  10  40  20  70
Opa-Locka        79  94  79  93 /  10  40  10  60
Homestead        79  93  79  92 /  10  30  20  60
Fort Lauderdale  80  93  80  92 /  10  30  10  50
N Ft Lauderdale  80  93  80  93 /  10  30  10  50
Pembroke Pines   80  93  80  93 /  10  40  10  50
West Palm Beach  79  94  78  94 /  10  40  10  50
Boca Raton       79  92  79  92 /  10  30  10  50
Naples           79  91  79  91 /  10  20  10  40

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...Heat Advisory until 6 PM EDT this evening for FLZ071>074-172>174.

AM...None.
GM...None.
&&

SHORT TERM...Redman
LONG TERM....Redman
AVIATION...DPB

Special Weather Statement
National Weather Service Miami FL
512 PM EDT Fri Aug 21 2026

FLZ063-212145-
Glades FL-
512 PM EDT Fri Aug 21 2026

...A strong thunderstorm will impact portions of northeastern Glades
County through 545 PM EDT...

At 511 PM EDT, National Weather Service meteorologists were tracking
a strong thunderstorm 7 miles northeast of Brighton Seminole
Reservation, or 7 miles west of Buckhead Ridge, moving north at 5
mph.

HAZARD...Wind gusts of 50 to 55 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Buckhead Ridge.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

These winds can down small tree limbs and branches, and blow around
unsecured small objects. Seek shelter in a safe building until the
storm passes.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 2720 8094 2719 8091 2718 8091 2717 8090
      2717 8088 2715 8087 2713 8089 2712 8091
      2710 8091 2710 8093 2709 8093 2709 8095
      2708 8095 2711 8111 2721 8111 2721 8094
TIME...MOT...LOC 2111Z 194DEG 5KT 2717 8100

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...55 MPH

NMP