Severe Thunderstorm Warning 103, NWS Miami, FL

Area Forecast Discussion
National Weather Service Miami FL
323 PM EDT Tue Sep 19 2023

...New LONG TERM...

.SHORT TERM...
(Rest of today through Wednesday)
Issued at 1225 PM EDT Tue Sep 19 2023

A stalled boundary separates a moist airmass over southern
Florida from drier air over northern Florida. The boundary extends
over the Atlantic to a parent area of low pressure over the Great
Lakes and eastern Canada. As the parent low advances north and
east, the boundary will drift north allowing the deeper moisture
to become well-entrenched over much of Florida by mid-week. Very
broad high pressure will attempt to build in, particularly at the
mid-levels with the deamplification of the longwave trough that
has persisted over the eastern United States.

Sea breezes are expected to develop daily with plenty of moisture
to support shower and thunderstorm activity over land during the
afternoon and evening and a land breeze to help keep activity
going over the local waters during the overnights and early
mornings. Maximum temperatures will be in the upper 80s to lower
90s across the region with heat index values reaching into the
triple digits. Overnight low temperatures will dip into the 70s
though some portions of the Atlantic coast will remain near 80.
The largest relief in temperatures at times could be from rain-
cooled air in the evenings/early overnights.

The lack of flow to support quick storm motions means that the
risk of excessive rainfall continues to exist. The large amount of
coverage forecast between today and Wednesday will require
monitoring rainfall trends in case flooding develops or we reach
sufficient saturation to bring a Flood Watch into consideration.
Current forecast trends favor the higher accumulations over
Southwest Florida but those vulnerable urban sections of Southeast
Florida are also in play for excessive rainfall.

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 323 PM EDT Tue Sep 19 2023

As subtropical ridging builds and establishes its position over the
far southern U.S. and Mexico regions, troughing will be enhanced
over the eastern Seaboard towards the end of the week and into the
weekend. A low pressure center will develop in response to the
deepening trough likely in the nearshore western Atlantic waters
near Georgia and the Carolinas by week's end. This low could become
cut off and thus progress very slowly northwards through the
weekend.

Since the low will be off to the north and east of our area, the
flow pattern will set up such that drier air gets filtered in across
the Florida Peninsula and this would decrease the widespread
potential for convective showers and thunderstorms Friday-Sunday.
However, the northerly flow will lead to cooler temperatures aloft
with 500mb temps approximately between -9 to -11C, which could bring
the potential for a few near severe or marginally severe storms over
the weekend. Mid-level lapse rates are anticipated to be weak as
instability will be largely favored in the low levels, but if there
is enough clearing then storms could grow quickly. Nonetheless,
expect less widespread convection for Fri-Sun with PoPs down to the
50-60% in general for those days.

The pattern for early next week to end the forecast period becomes
much more uncertain, but overall it looks to remain active as
guidance hints at flow shifting back out of the south and bringing
increased moisture return. Temperatures for the period are expected
to be in the upper 80s to low 90s for highs across the region and
low to mid 70s for lows.

&&

.AVIATION...
(18Z TAFS)
Issued at 1225 PM EDT Tue Sep 19 2023

Intermittent periods of sub-VFR as showers and thunderstorms
could impact terminals through the period. Convective focus will
shift inland though some cells could remain near the terminals
with the slow storm motion. Short-fused AMDs will likely be
necessary for IFR/LIFR at directly-impacted terminals.

&&

.MARINE...
Issued at 1225 PM EDT Tue Sep 19 2023

A moderate easterly wind regime is anticipated to prevail through
the middle of the week with wave heights forecast to remain
generally at or below 3 feet. A substantive coverage of convective
activity, including both showers and thunderstorms, is forecast
to persist through the week and potentially in the upcoming
weekend.

&&

.BEACHES...
Issued at 1225 PM EDT Tue Sep 19 2023

Although the residual NE swell is gradually subsiding over the
area, an elevated risk of rip currents is likely to persist for
the Atlantic beaches through the mid-week as easterly flow becomes
established.

&&

.PRELIMINARY POINT TEMPS/POPS...
Miami            78  89  76  87 /  60  80  60  80
West Kendall     76  90  75  89 /  50  80  60  80
Opa-Locka        77  89  76  88 /  50  80  60  80
Homestead        77  88  76  88 /  60  80  60  80
Fort Lauderdale  77  88  76  86 /  60  80  70  80
N Ft Lauderdale  77  88  76  87 /  60  80  70  80
Pembroke Pines   77  88  76  87 /  50  80  60  80
West Palm Beach  76  88  74  86 /  60  80  70  80
Boca Raton       77  89  76  87 /  60  80  70  80
Naples           76  91  75  90 /  50  80  50  80

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Wednesday evening for FLZ168.

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

SHORT TERM...RAG
LONG TERM....Redman
AVIATION...RAG

Hazardous Weather Outlook
National Weather Service Miami FL
332 PM EDT Tue Sep 19 2023

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
201945-
Lake Okeechobee-Biscayne Bay-
Coastal waters from Jupiter Inlet to Deerfield Beach FL out 20 NM-
Coastal waters from Deerfield Beach to Ocean Reef FL out 20 NM-
Waters from Jupiter Inlet to Deerfield Beach FL from 20 to 60 NM-
Waters from Deerfield Beach to Ocean Reef FL from 20 to 60 NM
excluding the territorial waters of Bahamas-Glades-Hendry-
Inland Palm Beach County-Metro Palm Beach County-
Coastal Collier County-Inland Collier County-Inland Broward County-
Metro Broward County-Inland Miami-Dade County-
Metropolitan Miami Dade-Mainland Monroe-Coastal Palm Beach County-
Coastal Broward County-Coastal Miami Dade County-Far South Miami-
Dade County-
Coastal waters from Chokoloskee to Bonita Beach FL out 20 NM-
Coastal waters from East Cape Sable to Chokoloskee FL out 20 NM-
Waters from Chokoloskee to Bonita Beach FL from 20 to 60 NM-
332 PM EDT Tue Sep 19 2023

...Numerous Thunderstorms This Afternoon and Evening...
...Localized Flooding Possible - Metropolitan East Coast...
...Palm Beaches: High Rip Current Risk...

This Hazardous Weather Outlook is for Atlantic coastal waters,
southeast Florida, southern Florida, southwest Florida and Gulf of
Mexico.

.DAY ONE...This afternoon and tonight.

Thunderstorms: Scattered to numerous thunderstorms will likely
develop this afternoon into the early evening hours. The strongest
thunderstorms could contain gusty winds and heavy downpours.

Flooding: Heavy downpours from thunderstorms could cause localized
flooding, particularly along recently soaked urban metropolitan
regions.

Heat: Heat indices peaking around 100 to 105 degrees will be
observed across many locations today.

Rip Currents: A high risk for rip currents will persist across the
Palm Beaches today, with a moderate risk for the Broward beaches.

Waterspouts: Isolated waterspout activity is possible over the local
waters.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Scattered to numerous showers and thunderstorms will be possible
each afternoon into next week. The strongest thunderstorms could
contain heavy downpours and gusty winds.

Peak heat indices will continue to be into the 100 to 105 range
through much of the upcoming week.

The rip current risk will remain high across the Palm Beaches into
early next week. Broward and Miami-Dade beaches will also see
elevated, and potentially high, rip current risks into early
portions of this upcoming week.

Towards the end of the week, there is potential for severe
thunderstorm development in association with an upper low developing
over the Gulf of Mexico.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report high wind, hail, and
flooding to the National Weather Service forecast office in Miami.

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Special Weather Statement
National Weather Service Miami FL
403 PM EDT Tue Sep 19 2023

FLZ063-066-192030-
Hendry FL-Glades FL-
403 PM EDT Tue Sep 19 2023

...A strong thunderstorm will impact portions of northeastern Hendry
and south central Glades Counties through 430 PM EDT...

At 402 PM EDT, National Weather Service meteorologists were tracking
a strong thunderstorm near Moore Haven, moving north at 10 mph.

HAZARD...Winds in excess of 30 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Moore Haven, Montura and Lake Hicpochee.

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.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 2693 8100 2689 8100 2688 8097 2664 8103
      2665 8129 2694 8130
TIME...MOT...LOC 2002Z 191DEG 8KT 2676 8116

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH

GR