Lightning Strike in Florida, August 4, 2020

Area Forecast Discussion
National Weather Service Miami FL
115 PM EDT Tue Aug 4 2020

.Aviation (18Z TAFs)...

Scattered showers and storms will continue along the east coast
through the early evening hours. Periods of sub-VFR conditions are
likely at times, especially for TMB/MIA/FLL/FXE. Winds have
shifted from the SW at MIA/OPF recently in association with an
outflow boundary, but S-SE winds should otherwise prevail. Storms
ending this evening with light and variable winds overnight.

&&

.Prev Discussion... /issued 917 AM EDT Tue Aug 4 2020/

Aviation...

Shower and thunderstorm coverage should increase over the next few
hours and continue through the early evening hours. Prevailing
VFR, but lower CIGS/VSBYS certainly possible if a thunderstorm
directly impacts any airfield. Light S-SE winds for the east coast
with gusty and erratic winds possible in and near thunderstorms.

Update...

Upper troughing will advance through the eastern states as
Tropical Storm Isaias tracks from the Mid Atlantic region towards
New England. A corridor of deep moisture remains in the wake of
Isaias from the Caribbean Sea into South Florida, as evidenced by
the 04.12Z MFL sounding showing a precipitable water value of
2.17 inches. This should result in scattered to numerous showers
and thunderstorms today given the expected forcing for ascent
along numerous low-level boundaries. The primary weather related
hazard remains the potential for localized flooding of urban and
poorly drained areas today. This threat should be most
concentrated along the east coast metro areas given the very
light southerly steering flow along with a slight onshore
component in the low levels. A few stronger wind gusts are also
possible today from any taller thunderstorm cores as they
collapse.

Prev Discussion... /issued 306 AM EDT Tue Aug 4 2020/

Discussion...

Short Term (Today through Wednesday Night)...

GOES-16 water vapor imagery this morning reveals robust troughing
across the eastern CONUS that extends into the northern Gulf of
Mexico, while the subtropical ridge remains situated just to our
east in the latest 06Z WPC surface analysis. These two features are
working in concert to aid S/SW flow in lofting a continuous plume of
tropical moisture across South Florida in the wake of Isaias as it
recurves towards the NE.

With that said, ample moisture in place, sufficient daytime heating,
lifting mechanisms via mesoscale boundaries, and the proximity of the
trough axis to the region indicate the atmosphere remains ripe for
convective initiation today and tomorrow. Hence showers and
thunderstorms are noted on radar early this morning along subtle
boundaries, mainly over the local waters. Activity should transition
over land through the afternoon and become more scattered to
numerous across South Florida before dissipating by early evening.

PWATs of 2+ inches noted in forecast soundings could translate into
a hydro concern, especially for the east coast metro where the S/SW
steering flow and subsequent outflow boundaries could result in
repeated rounds of heavy rainfall over urban and poorly drained
areas. Therefore, flooding is the primary concern with convection,
with gusty winds and frequent lightning as additional hazards
that could materialize with the strongest storms.

Additionally, heat indices today will range between 103 to 106.
While values are currently forecast to remain below advisory
criteria, areas to monitor as the day unfolds include Palm Beach and
the southwestern portions of South Florida. Otherwise, daytime
temperatures will soar each day into the lower 90s and only drop
into the mid to upper 70s to near 80 along the east coast
overnight.

Long Term (Thursday through Monday night):

Latest model solutions depict a mid level trough dominating most of
the eastern seaboard and into the Florida panhandle for the end of
the work week. Meanwhile, high pressure centered over the central
Atlantic will gradually build back into the area in the wake of
Isaias. But global models dont expand the W periphery of the ridge
enough to bring a typical easterly flow across the area, with
basically southerly/southeasterly flow establishing. Combined with
the aforementioned trough, the overall synoptic flow will result
in abundant tropical moisture advection from the Gulf region and
into the Florida Peninsula.

With the described synoptic scenario in place, expect increasing
chances of rain, along with potential for a few strong
thunderstorms each afternoon. Coverage will be widespread,
especially Thursday afternoon. But with the increased cloud cover
and shower activity, temperatures should then drop to near or at
normals.

For the weekend and into early next week, the ridge expands a little
more into the area, and the axis migrates into the northern
portions of SoFlo, bringing back a more typical summer pattern
dominated by afternoon sea breeze boundaries.

Marine...
Generally weak, southerly flow will remain across the local
waters through mid-week before high pressure builds into the
region, swinging winds out of the east by the weekend. Outside
of typical summertime showers and thunderstorms, relatively
benign boating conditions are expected.

Aviation (06Z Tafs)...
Dry, VFR conditions will prevail across all South Florida
terminals overnight, with coverage of SHRA/TSRA increasing around
12Z and continuing through 03Z. Sub-VFR vis and cigs, along with
gusty, erratic winds are possible if activity moves over the
airfields, but will handle with short-fused amendments.
&&

.Preliminary Point Temps/PoPs...
West Palm Beach  77  90  77  90 /  40  80  20  70
Fort Lauderdale  79  89  79  89 /  50  70  20  70
Miami            78  89  78  90 /  50  70  20  80
Naples           77  91  77  91 /  40  70  40  80

&&

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

Update/Aviation...34/SPM
Short Term/Marine/Aviation...11/HVN
Long Term...17

Hazardous Weather Outlook for South Florida
National Weather Service Miami FL
812 AM EDT Tue Aug 4 2020

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
050015-
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-Metro Palm Beach-Coastal Collier-Inland Collier-
Inland Broward-Metro Broward-Inland Miami-Dade-Metro Miami-Dade-
Mainland Monroe-Coastal Palm Beach-Coastal Broward-Coastal Miami-
Dade-Far South Miami-Dade-
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-
812 AM EDT Tue Aug 4 2020

...Localized Flooding Possible Today East Coast Metro Areas...

This hazardous weather outlook is for South Florida.

.DAY ONE...TODAY AND TONIGHT

Thunderstorms: Showers and thunderstorms this morning over the local
waters should become more scattered to numerous across the Florida peninsula
this afternoon and evening. Lightning is the main hazard.

Flooding: Localized flooding may be possible across urbanized or poor
drainage areas, especially if multiple storms move over the same
locations in a short amount of time across the east coast metro
areas.

Wind: The strongest storms may be capable of producing an isolated
wind gust up to 45 mph this afternoon and evening.

Waterspouts: A few waterspouts are possible over all South Florida
waters.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

Scattered thunderstorms are forecast each day, primarily during the
afternoon hours. Gusty winds, lightning, and localized flooding over
urban and poorly drained areas from heavy rainfall may be possible.

.SPOTTER INFORMATION STATEMENT...

Widespread spotter activation is not anticipated, however individual
spotters are encouraged to report high wind, hail and flooding to
the National Weather Service forecast office in Miami.

For more information...visit the National Weather Service in
Miami website at www.weather.gov/miami.