Special Weather Statement, NWS Melbourne, FL

Area Forecast Discussion
National Weather Service Melbourne FL
353 PM EDT Tue Jul 17 2018

.DISCUSSION...
Current-Tonight...Latest radar imagery shows isolated to scattered
thunderstorms advancing eastward across the state, with coverage
increasing to the southwest. Dominant SW flow has confined the
east coast sea breeze to the immediate coast south of Cape
Canaveral, thus a late afternoon boundary collision is likely
along I-95 towards the barrier islands. Latest 15Z XMR sounding
shows slight drying near the surface, allowing for the potential
of gusty winds in strongest convection this afternoon/early
evening. Southwest flow will quickly push showers and storms
offshore tonight, with most convection wrapping up near 00Z.

Limited cloud cover combined with southwesterly flow allowed
temperatures across east central FL to climb to the mid 90s today
with heat indices soaring above 100F.

Tomorrow...Trough dipping into the Deep South will continue to
suppress high pressure over the Atlantic. Weak ridge axis remains
positioned over south FL, continuing strong S/SW flow over the area.
A similar setup expected as today, with the suppression of the east
coast sea breeze in dominant SW flow. PWATs near 2.00" will keep
PoPs hovering near 50% from Melbourne northward. A dry pocket
filters in over Lake Okeechobee, leaving PoPs 30-40% for the
Treasure Coast. Isolated to scattered showers and storms will
advance eastward across the state, with most convection ending near
sunset.

Slightly above normal high temps persist in the low 90s inland,
approaching the mid 90s along the coast with the lacking sea breeze.
Heat indices soar to 102-105F.

Thurs-Mon... Persistent troffing pattern east of the MS River
Valley will keep the axis of the Bermuda Ridge suppressed over the
south FL Peninsula/FL Straits for the next several days. This, in
turn, will result in W/SW flow thru the lcl column that will
favor the east central peninsula for diurnal precip: Westerly flow
will push the west coast sea breeze rapidly inland while keeping
the east coast breeze pinned along the I-95 Corridor, while
westerly mid lvl steering flow packs shra/tsra activity along the
east FL Coast.

Primary factor for daily precip coverage will be low/mid lvl
moisture, which the latest RAP40 analysis shows is, by and large, on
the low side acrs the region. While current PWat readings on the
order of 2.00", acrs the SE GOMEX/NW Carib RAP40 shows H100-H70 mean
RH values largely AOB 70pct, H85-H50 dewpoint depressions 10-15C,
and PWat values dropping to arnd 1.50".

Diurnal heating will provide sufficient instability to trigger
shra/tsra activity each day, but the general lack of regional
moisture will tend to limit overall coverage.  Latest GFS MOS
guidance seems to have a reasonable handle on this trend with PoPs
generally AOB 50pct. H70 temps arnd 9C and H50 temps arnd -7C will
yield lapse rates arnd 6.0C/KM, so strong/svr storm threat will be
low. Will go with a 50-60pct coverage on Thu, trending down to 30-
50pct coverage into early next week. Temps slightly abv avg due to
the prevailing W/SW flow, aftn maxes in the L/M90s, mrng mins in the
M70s.

&&

.AVIATION...Mainly VFR to brief MVFR in scattered showers and
thunderstorms this afternoon and early evening, highest coverage
near KMCO to coastal terminals KDAB to KMLB. Pushing offshore and
weakening by 00Z. Skies will slowly clear to be VFR overnight.
Winds mainly light from the southwest, gusty to around 25 knots in
and near thunderstorms.

&&

.MARINE...
Tonight-Tomorrow...Weak ridge axis over the FL Straits will
continue stronger S/SW flow through the period, with winds 10-15
kts through tomorrow afternoon. Seas will remain 2-3 ft building
to 4 ft in the Gulf Stream waters late in the period. Afternoon
showers and thunderstorms will push offshore with highest coverage
north of Sebastian Inlet.

Thu-Mon...(previous) Troffing pattern over the ern seaboard will
keep the axis of the Bermuda ridge confined to the south FL
Peninsula/FL Straits, resulting in a gentle to moderate S/SW
breeze. Lcl pgrad will be tight enough to maintain a gentle to
moderate W/SW breeze acrs the lcl Atlc, enough to suppress the
formation of the east coast sea breeze until late aftn each day.
Even then, formation is only expected south of Cape Canaveral.
Seas generally 2-3FT...up to 4FT in the Gulf Stream north of
Sebastian Inlet. Sct-nmrs shra/tsras moving offshore each aftn.

&&

.HYDROLOGY...
The Saint Johns River is either above Action Stage
or just above Flood Stage between Geneva and Astor. Little change
is expected through late week.

Near Geneva, just south of Lake Harney, the most recent stage was
8.23 feet, which is above Flood Stage (8.0 feet). The river is
forecast to fall slightly but remain at or just above Flood Stage
into late week. A River Flood Warning remains in effect for this
area.

At Sanford, the most recent stage was 5.1 feet, which is above
Action Stage (4.2 feet). The river is forecast to remain nearly
steady, staying below Flood Stage (5.5 feet) into late week.

Near Deland, the most recent stage was 3.54 feet, which is just
above Action Stage (3.5 feet). The river is forecast to remain
nearly steady into late week.

At Astor, the most recent stage was 2.34 feet, which is just
above Flood Stage (2.3 feet). The river is forecast to remain
nearly steady into late week. A River Flood Warning remains in
effect for this area.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  76  91  76  91 /  20  50  30  60
MCO  76  93  76  92 /  20  50  10  50
MLB  77  94  77  92 /  20  50  20  40
VRB  75  94  75  93 /  30  40  30  30
LEE  77  91  77  91 /  20  50  10  60
SFB  76  93  76  93 /  20  50  20  60
ORL  76  92  77  92 /  20  50  10  50
FPR  75  94  75  93 /  30  40  30  30

&&

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

SHORT TERM...99
LONG TERM....99
AVIATION...99