Tornado in Florida, July 20, 2018

Area Forecast Discussion
National Weather Service Miami FL
403 PM EDT Fri Jul 20 2018

.DISCUSSION...

THIS AFTERNOON AND TONIGHT: As expected, dry air continues to limit
coverage of showers and storms this afternoon. The isolated activity
that has developed has been limited to the east coast metro where a
diffuse Gulf breeze is interacting with the Atlantic seabreeze
pinned along the coast. The remainder of this afternoon should
evolve similar to yesterday, with boundary-seabreeze interactions
driving widely scattered activity across the east coast metro
through just after sunset.

Forecast looks mainly dry for land areas overnight with the
potential for a few Atlantic showers to brush the coast at times.

THIS WEEKEND: Upper level low moving through the Great Lakes region
this afternoon will give the shortwave and low level trough that's
been stalled across Central Florida a southward push into this
weekend.

The boundary's progress will be slow, perhaps just making it to the
Lake Okeechobee region for the latter half of Saturday, then more
firmly settled across South Florida for Sunday. We will remain under
the influence of the ridge on Saturday, without a significant
moistening of the atmosphere. Rain chances will trend a little
higher towards the Lake, but coverage across the remainder of the
region will remain isolated to widely scattered at best, as with the
past few days.

Falling mid level heights, cooling temperatures aloft, and a
moistening atmosphere as the low level boundary makes it into South
Florida on Sunday will lead to widespread showers and storms into
Sunday afternoon. Most activity looks to initialize along the
boundary itself, so showers and storms look to get going relatively
early across the area.

NEXT WEEK: Upper level low at the southern end of the east coast
trough will continue to sink south into the Gulf early next week. As
we've seen a few times this summer, it looks to become a cut-off low
retrograding west along the northern Gulf coast through the week.

Main impacts from this feature look to be during the early part of
the week as the low is progged to be closest to us across North
Florida/NE Gulf. However, moist west-southwest flow (with PWATs
potentially well above 2"), along with cooler temperatures aloft and
smaller vort maxes rotating around the main low will bring
widespread showers and storms through much of the week. Current
model guidance suggests a pattern of more showers with embedded
storms, along with the potentially for locally heavy rainfall if
higher moisture levels materialize.

&&

.MARINE...Weak boundary across Central Florida will gradually settle
southward over the next few days. Moderate west-southwesterly flow
is expected to prevail as a result, with little if any development
of the Atlantic seabreeze. Seas continue 2 feet or less in both the
Gulf and Atlantic through Saturday, with the increasing westerly
fetch bringing seas to 3 to 4 feet in the offshore Gulf by Monday.
Coverage of showers and storms remains isolated on Saturday, with
more widespread coverage across all local waters into the upcoming
week.

&&

.AVIATION...Southerly to southwesterly flow at most sites has pinned
the Atlantic sea breeze close to the east coast terminals. Impacts
from TSRA could bring bouts of sub-VFR conditions to a terminal,
though confidence is not high enough to include any widespread
restrictions at this time. Short-fused amendments will be necessary
this afternoon. Convection should diminish in the evening with the
activity overnight focus over the waters.
Saturday is expected to be another relatively dry day though some
convection cannot be ruled out.

&&

.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach  77  94  76  93 /  20  20  20  60
Fort Lauderdale  79  93  79  93 /  20  30  10  50
Miami            78  93  77  92 /  10  30  10  40
Naples           78  92  78  90 /  10  10  30  50

&&

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

&&

DISCUSSION...88/ALM
MARINE...88/ALM
AVIATION...02/RAG

Hazardous Weather Outlook for South Florida...UPDATED
National Weather Service Miami FL
1129 AM EDT Fri Jul 20 2018

AMZ610-630-650-651-670-671-FLZ063-066>075-168-172>174-GMZ656-657-676-
210330-
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-
1129 AM EDT Fri Jul 20 2018

...SCATTERED THUNDERSTORMS MAINLY EAST COAST...
...HEAT INDEX UP TO 107 DEGREES ACROSS NORTHERN PALM BEACH COUNTY...

This hazardous weather outlook is for South Florida.

.DAY ONE...THIS AFTERNOON AND TONIGHT

Thunderstorms: Isolated to scattered thunderstorms are expected to
develop this afternoon and evening, mainly over the east coast metro
areas. The main threats should consist of heavy rain, cloud-to-
ground lightning strikes, small hail and gusty winds, particularly
over Palm Beach and Broward Counties this afternoon and evening.

Tornadoes: Funnel clouds and weak, short-lived tornadoes are possible
this afternoon and evening with thunderstorms interacting with
atmospheric boundaries, mainly around the east coast.

Waterspouts: Isolated waterspout activity will be possible today,
mainly over Lake Okeechobee and the Atlantic waters.

Wind: The strongest thunderstorms will be capable of producing wind
gusts up to around 50 mph, mainly over the east coast metro area
late this afternoon into the evening.

Hail: The strongest thunderstorms will be capable of producing small
hail to the size of pennies, mainly over the east coast metro area
late this afternoon into the evening.

Flooding: Heavy rainfall from thunderstorms this afternoon and
evening could lead to ponding or localize flooding in poor drainage
areas.

Temperatures: Heat index values will rise to 105 degrees across most
of South Florida today. Heat index will may rise up to 107 degrees
across portions of northern Palm Beach county and the Everglades.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

Isolated to scattered thunderstorms are forecast each afternoon and
early evening through the weekend over the interior region.
Lightning will be the main hazard.

High temperatures may rise a few degrees above normal in the low to
mid 90s through Thursday, potentially bringing several hours of heat
indices in the 102 to 107 degree range during the late morning and
early afternoon for the southern interior and Gulf Coast regions.

.SPOTTER INFORMATION STATEMENT...

Widespread spotter activation is not anticipated, however individual
spotters are encouraged to report high wind, funnel clouds,
waterspouts, 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.

RAG