Flood and Damaging Winds in Florida, November 23, 2017

Area Forecast Discussion
National Weather Service Melbourne FL
442 AM EST Thu Nov 23 2017

.DISCUSSION...

...High Rain Chances this Thanksgiving Day with Potential for
Isolated Strong Storms...

Today-Tonight...Weak front will linger near to north of Lake and
Volusia counties today as weak low over the eastern Gulf shifts E/NE
along this boundary ahead of a sharpening mid/upper level trough
over the Gulf. Deep moisture and disturbed flow aloft will lead to
high rain chances this Thanksgiving day, with PoPs ranging from 90
percent across Lake and Volusia counties to 70 percent across the
Treasure Coast. Numerous to widespread showers moving into areas
near to northwest of I-4 this morning, with this activity
spreading farther south and east through the afternoon. Models
keep greatest rainfall from this system across north Florida
through tonight, but still may see widespread amounts up to 1-2
inches across areas north of Orlando.

In terms of thunderstorm development, southern areas from
Okeechobee County to the Treasure Coast will have a better shot to
see some breaks in the clouds initially today, leading to greater
heating and instability. However, better dynamic support for lift
and low level convergence near the front will exist across
northern areas. Therefore the potential for a few thunderstorms
will exist across all of east central Florida today into tonight.
Isolated stronger storms will be possible, with the main threats
being dangerous lightning strikes, strong gusty winds and locally
heavy rainfall. However, cold temperatures aloft and marginal
shear profiles may support small hail and/or isolated brief
tornado threat.

Friday...A trough aloft extending well southward into the Gulf of
Mexico will slowly translate eastward while gradually filling. At
the surface, rather weak low pressure along a quasi-stationary
frontal boundary over the eastern Gulf will eventually push across
central FL by Fri night and pull the frontal boundary through the
area.

The 00Z GFS and ECMWF show some drier air moving into our northern
sections during the afternoon so rain chances should gradually
decrease during the day across the north. Also, best thunder
chances should shift offshore as the day progresses. Will maintain
higher rain chances across the south along with thunder as temps
aloft will be quite cold (-12C to -13C at 500 mb). But
considerable clouds will limit heating/instability and low level
winds/shear will not be particularly strong so threat for strong
storms looks low.

Saturday-Wednesday...A cooler and drier airmass will overspread the
area this weekend behind initial front early Sat and probably a
reinforcing surge late Sun. The models quickly veer the low level
flow to onshore on Mon. Max/min temps look to be only a few
degrees from average (which are mid-upper 70s and mid-upper 50s).
The breezy onshore flow may start to push a few Atlantic showers
ashore Mon. As is typical for these return flow cases, the early
week MOS POPs are quite low, but will maintain some slight shower
chances for now.

&&

.AVIATION...VFR conditions will generally continue through mid
morning with a few showers producing tempo IFR/MVFR conditions. More
predominant vis/cig reductions will occur into the late morning and
afternoon as numerous to widespread showers and isolated storms
develop and move eastward across the area. Rain chances will then
decrease into the overnight hours, but lingering IFR/MVFR cigs will
likely persist over much of the area.

&&

.MARINE...
Today-Tonight...Frontal boundary lifting northward across the area
will settle near to north of the Volusia County waters. E/SE flow
around 10-15 knots will become S/SW by late day. A surge in
northerly flow, around 15-20 knots is then indicated over the
Volusia waters into late tonight as weak low along the boundary
moves off the coast and boundary shifts southward. This will help
build seas to 6-7 feet over the northern waters, with a Small Craft
Advisory going into effect late tonight, north of the Volusia-
Brevard County line.

Fri...The first wave of low pressure is forecast to scoot NE of
the area and push the frontal boundary down into our northern
waters Fri. This should result in an increase in north winds 15-20
knots behind the boundary and seas 5-7 feet over the Volusia
waters. So Small Craft Advisory will be in effect there. The north
winds will push into the Brevard waters as well though winds and
seas do not look to reach Advisory criteria but a Caution headline
will be warranted. Across the southern waters, winds should be
less than 10 knots but they could be strong/gusty near numerous
showers and isolated storms.

Sat-Sun...The frontal boundary should push south of the waters by
early Sat. Post frontal winds on Sat out of the northwest look to
be around 15 knots then a reinforcing surge of northerly winds
late Sun is indicated with similar speeds. So while the weather
will improve over the weekend, winds look poor for small craft
operation, especially in the Gulf Stream, where seas to 6 feet are
expected.

Mon...High pressure building to the Carolina coast will generate a
breezy northeast-east wind flow and choppy conditions will occur
on all of the Atlantic waters.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  73  64  71  58 /  90  60  50  10
MCO  75  64  73  58 /  80  50  40  10
MLB  79  65  77  62 /  80  50  50  20
VRB  80  65  78  61 /  70  50  50  20
LEE  73  62  71  56 /  90  60  40  10
SFB  74  63  73  57 /  90  60  40  10
ORL  75  64  73  59 /  80  60  40  10
FPR  80  64  79  61 /  70  50  50  20

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory from 4 AM to 7 PM EST Friday for Flagler
     Beach to Volusia-Brevard County Line 0-20 nm-Flagler Beach
     to Volusia-Brevard County Line 20-60 nm.

&&

SHORT TERM...Weitlich
LONG TERM....Kelly

Hazardous Weather Outlook
National Weather Service Melbourne FL
451 AM EST Thu Nov 23 2017

AMZ550-552-555-570-572-575-FLZ041-044>047-053-054-058-059-064-141-
144-147-240000-
Flagler Beach to Volusia-Brevard County Line 0-20 nm-Volusia-
Brevard County Line to Sebastian Inlet 0-20 nm-
Sebastian Inlet to Jupiter Inlet 0-20 nm-Flagler Beach to Volusia-
Brevard County Line 20-60 nm-Volusia-
Brevard County Line to Sebastian Inlet 20-60 nm-
Sebastian Inlet to Jupiter Inlet 20-60 nm-Inland Volusia County-
Northern Lake County-Orange-Seminole-Southern Brevard County-
Osceola-Indian River-Okeechobee-St. Lucie-Martin-
Coastal Volusia County-Southern Lake County-
Northern Brevard County-
451 AM EST Thu Nov 23 2017

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL FLORIDA.

.DAY ONE...TODAY AND TONIGHT.

.THUNDERSTORM IMPACT...
Numerous to widespread showers will cross central Florida today
ahead of a weak low pressure system over the eastern Gulf.
Isolated thunderstorms will also develop across the area, mainly
during the afternoon hours. A few stronger storms will be
possible, with the main threats being dangerous lightning
strikes, small hail, strong wind gusts up to 40 to 50 mph, and
locally heavy rainfall of 1 to 2 inches. While threat remains low,
an isolated threat for damaging winds around 60 mph and a brief
tornado will also exist.

.RIP CURRENT IMPACT...
A moderate risk of rip currents will exist along the beaches of
east central Florida today. When arriving at the beach, check with
ocean rescue personnel on the latest surf conditions and always
swim near a lifeguard.

.MARINE THUNDERSTORM GUST IMPACT...
Isolated thunderstorms will develop across the area, mainly during
the afternoon. Any storms will have the potential to produce wind
gusts in excess of 34 knots as they move northeast up to 30 to 35
mph across inland lakes and offshore.

.WATERSPOUT IMPACT...
Any stronger storms that push offshore or that develop over the
coastal waters will have the potential to produce brief isolated
waterspouts.

.WIND AND SEA IMPACT...
Northerly winds will increase to 15 to 20 knots after midnight,
building seas to 6 to 7 feet over the coastal waters of Volusia
County. A Small Craft Advisory goes into effect for these waters
late tonight for these hazardous boating conditions.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.
An unsettled weather pattern will continue through late week with
scattered showers and isolated thunderstorms continuing into
Friday. A few stronger storms will be possible with locally heavy
rainfall, gusty winds and dangerous lighting strikes being the
main thunderstorm hazards.

Seas will continue to build up to 6 to 7 feet over the offshore
waters, and nearshore north of Sebastian Inlet into Friday,
producing poor to hazardous boating conditions.

.SPOTTER INFORMATION STATEMENT...
Spotters are requested to monitor the weather and self activate
if needed.

Weitlich

PRELIMINARY LOCAL STORM REPORT
National Weather Service Melbourne FL
204 AM EST THU NOV 23 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1240 AM     HEAVY RAIN       COCOA BEACH             28.33N 80.62W
11/23/2017  M3.56 INCH       BREVARD            FL   MESONET

            WEATHER UNDERGROUND SITE, KFLCOCOA61 AT LORI WILSON PARK,
            MEASURED 3.56 INCHES OF RAIN BETWEEN 1120PM-1240 AM.

&&

KELLY