Special Weather Statement, NWS Melbourne, FL

East Central Florida Forecast Discussion
National Weather Service Melbourne FL
10 AM EDT Thu Jun 28 2018

.DISCUSSION...
XMR sounding this morning shows H5 temp has warmed to -6.1C with
light steering level wly winds 5 to 10 kt. Expect slow moving
activity ascd with seabreezes from both coasts to form independently
from late morning into the afternoon with eventual larger scale
collision inland toward late afternoon. Slow migration of the west
coast breeze and its ascd convection ewd should focus the bulk of
late activity along with locally heavy rain threats over the local
forecast area later today into evening.

The main contribution for the expected lightning storms will be
strong surface heating and numerous boundary interactions.
Precipitable water ~46 mm will allow for some locally heavy rains to
occur given slow movement of activity. Main hazard will be lightning
and heavy rain. Strong wind gusts of 45 to 50 mph will be possible
in the stronger cells. The present forecast remains valid.

prev disc...

Today-Tonight...Surface trough over the eastern seaboard will keep
axis of Atlantic high pressure ridge suppressed to our south.  Mid
level shortwave energy will stay north of the area, but a break is
indicated in the subtropical ridge vicinity of the Florida
peninsula. Therefore, no cap or suppression is indicated and
moisture will remain quite high. 500mb temps are forecast about
minus 7C, which would be a degree cooler than yesterday.

With weak low-mid level west/northwest winds, expect convection will
progress west to east across the peninsula this afternoon.  The
HRRR model is also showing scattered showers/storms forming along
the east coast sea breeze. Strong boundary interactions will occur
near the east coast by late afternoon and extend into early evening.
A few strong storms with frequent lightning strikes and gusty
winds.

MOS PoPs again look too low in the north (20%), but range to 60%
in the south. None of the other models suggest those lower values.
Will follow the HRRR model, which has been indicating likely PoPs
for most of the area.

High level debris cloudiness is a little greater at this hour
compared to 24 hours ago, but do not expect these clouds will be
opaque enough to significantly inhibit daytime heating. However,
with scattered to numerous showers/storms in the forecast, have
undercut interior MOS highs (which have been too high most of the
month).

&&

.AVIATION...Mostly VFR this morning, then another round of scattered
to numerous showers and storms will march west to east across the
peninsula this afternoon and evening. A few storms will be strong,
especially near the coastal terminals. In addition to IFR conditions,
frequent lightning strikes will occur and there is a potential for
gusty winds 35-45 knots.

&&

.MARINE...
Today-Tonight...The gradient wind will continue to be southwest-west
as the Atlantic high pressure ridge axis remains south of the
waters.  Speeds will be 10 knots or less and seas 2 feet or less.
The main mariner concern will be storms that form over the mainland
this afternoon.  A few should push to the coast with gusty winds up
to around 35 knots possible, which also should affect the nearshore
Atlantic waters.

For this weekend, gentle to moderate breezes are expected, decreasing
as the work week starts and through the holiday. Seas will remain
generally at 2 to 3 feet.

&&

.HYDROLOGY...The Saint Johns River above Lake Harney near Geneva will
remain above Action Stage through at least the next five days.
Locally heavy rainfall early this week caused a slight rise in the
river. Any additional heavy rainfall at this location will lead
to additional slow rises. Although the river is forecast to remain
just below minor Flood Stage it will have to be monitored closely
for the possibility of equaling or exceeding flood stage given
the persistent summertime showers and storms which are forecast
daily into next week.

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.

&&

JP/MRV

Hazardous Weather Outlook...UPDATED
National Weather Service Melbourne FL
1127 AM EDT Thu Jun 28 2018

AMZ550-552-555-570-572-575-FLZ041-044>047-053-054-058-059-064-141-
144-147-290330-
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-
1127 AM EDT Thu Jun 28 2018

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL FLORIDA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

.THUNDERSTORM IMPACT...
A light westerly wind flow will lead to numerous boundary interactions
over east central Florida during the afternoon and evening. This,
combined with a moist airmass in place, will generate scattered
to numerous showers and storms. Initially this activity will
move into Lake County and develop along the east coast sea breeze
from early to mid afternoon. Coverage and intensity of storms
will then increase through late day as outflow and sea breeze
boundaries collide near to inland of I 95.

The main hazard will be from lightning strikes, which will be
frequent in a few strong storms. Move inside as skies begin to
look threatening. Locally heavy rainfall will also occur. A few of
the strongest storms may also produce gusty winds up to 45 to 55
mph in the late afternoon and early evening from metro Orlando and
inland Volusia county to the east coast.

.FLOOD IMPACT...
Storm motion will be slowly to the east or southeast, so a few
stronger storms will be capable of dumping around 3 inches of rain
in a 60 to 90 minute period. This would cause considerable
ponding of water on roadways and other poorly drained areas.

.MARINE THUNDERSTORM GUST IMPACT...
A few storms over land areas, particularly along the east coast
sea breeze, will become strong and produce wind gusts around 40
mph. Storms are expected to move slowly to the east or southeast,
so mariners on inland lakes and along the coast should move to
safe harbor as skies darken to the west.

.RIVER FLOOD IMPACT...
The Saint Johns River above Lake Harney near Geneva will remain
above Action Stage through at least the next five days. Locally
heavy rainfall early this week caused a slight rise in the river.
Any additional heavy rainfall at this location will lead to
additional slow rises. Although the river is forecast to remain
just below minor Flood Stage, it will be monitored closely for
the possibility of equaling or exceeding flood stage, given the
persistent summertime showers and storms which are forecast daily
into next week.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.
Scattered to numerous showers and storms are expected through the
period each afternoon and evening. A few strong storms with
frequent lightning strikes and quick 2 to 3 inch downpours are
expected each day where boundary interactions are most vigorous.

.SPOTTER INFORMATION STATEMENT...
Spotters are requested to monitor the weather and self activate
if needed. Rainfall observers should report amounts of 2 inches
or greater to the National Weather Service in Melbourne.

Volkmer/Lascody

Special Weather Statement
National Weather Service Melbourne FL
143 PM EDT THU JUN 28 2018

FLZ044>046-281830-
Northern Lake County FL-Orange FL-Seminole FL-
143 PM EDT THU JUN 28 2018

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN SEMINOLE...NORTHEASTERN
LAKE AND CENTRAL ORANGE COUNTIES UNTIL 230 PM EDT...

At 142 PM EDT, Doppler radar was tracking a strong thunderstorm near
Cassia, moving southeast at 10 mph. Additional strong storms were
developing across western Seminole county that will move southeast
into central Orange county.

Wind gusts in excess of 45 mph will be possible with this storm.

Locations impacted include...
Orlando, Sanford, Apopka, Altamonte Springs and Ocoee.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 2920 8161 2920 8159 2891 8136 2890 8135
      2889 8137 2886 8135 2885 8136 2883 8130
      2844 8099 2847 8144 2894 8171 2896 8166
      2905 8166 2906 8164 2926 8164
TIME...MOT...LOC 1742Z 303DEG 9KT 2889 8155

15

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