006
FXUS62 KMLB 182011
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
411 PM EDT Wed Sep 18 2024

...New DISCUSSION, MARINE, HYDROLOGY...

.DISCUSSION...
Issued at 410 PM EDT Wed Sep 18 2024

Key Messages:

- Afternoon shower and lightning storm chances persist through
  late week, lowering this weekend

- High astronomical tides promote elevated water levels this week,
  a Coastal Flood Advisory continues

- Saint Johns River at Astor forecast to remain in Moderate Flood

Now-Tonight...A warm Wednesday afternoon is well under way as
low-mid level cumulus clouds billow from southwest to northeast
across central Florida. Despite some of these clouds, it is
practically impossible to avoid the heat today with plenty of
sunshine pushing temperatures into the low 90s. Heat indices are
eclipsing the 100 degree mark in several locations, especially
along the Atlantic coast. Conditions will remain hot through early
evening, except where a rain shower moves overhead.

Speaking of rain, showers and lightning storms are expected to
build in coverage over the next few hours, especially from Cape
Canaveral to the Treasure Coast. With the east coast sea breeze
pinned along the immediate coast (and rather diffuse in most
locations), any sea breeze collision that leads to additional
showers and storms will be skewed to the late afternoon or early
evening. RAP analysis shows 2000-2500+ J/kg of MLCAPE, little in
the way of bulk shear, and a sharp contrast between steep low-
level lapse rates (8.0 C/km) and weak mid-level lapse rates
(5.5-6.0 C/km). GOES-derived PW indicates better moisture
availability across the southern half of the forecast area, and
hi-res models show a brief surge of ~2.0" PW through 00z up and
down the FL Atlantic coast. Therefore, the primary window for
scattered lightning storms will likely be between 5 PM and 11 PM
tonight. Gusty winds, frequent lightning strikes, and brief heavy
rainfall will be the main threats. However, any microscale
convective collisions (sea breeze/outflow boundaries) may allow a
more organized storm to exhibit brief low-level rotation. That
said, the tornado and waterspout threat remain very low.

Rain and storms will be moving offshore or dissipating across
southern locations by midnight, leaving behind gradually clearing
skies and temperatures falling into the 70s. A Coastal Flood
Advisory remains in effect for some flooding of low-lying areas
along the Atlantic shoreline, mainly around times of high tide. A
high risk of life-threatening rip currents also continues at area
beaches.

Thursday-Friday...Thursday`s forecast is very similar to today`s,
with lows starting out in the 70s under mostly clear conditions.
Light northwesterly flow in the morning will turn onshore in the
afternoon as the east coast breeze makes more of an attempt to
meander inland. Isolated to scattered showers and a few lightning
storms are expected, mainly toward late afternoon and early
evening, with a focus from Melbourne southward to Lake Okeechobee.
A good number of locations, especially farther north, will escape
without a raindrop Thursday afternoon. This means temperatures
will be able to climb into the low 90s with no issue, and heat
index values are forecast to push into the low 100s once again.

Weak mid level troughing and northwesterly flow sticks around
through Friday. An approaching (weak) surface front arrives Friday
morning and continues south through the remainder of the day,
eventually stalling across the Florida Straits into this weekend.
PoPs decrease to around 20-30 percent (north) and 40-50 percent
(south) on Friday as a result of the frontal passage and some dry
air advection. Winds do increase a bit behind the front as they
veer to the northeast during the afternoon. Temperatures will not
reflect much of a frontal passage, but a degree or two cooler for
highs (upper 80s/low 90s) is reflected in Friday`s forecast.

Saturday-Tuesday...Drier conditions are expected this weekend with
the highest rain chances confined to south Florida. Northeasterly
winds may become gusty each afternoon, especially from Sunday into
next week. Mid level ridging builds east from the western Gulf of
Mexico to the southeast U.S. early in the week, while surface high
pressure expands over the eastern U.S. Our next formidable rain
opportunity could arrive with a push of tropical moisture by mid
to late week. The National Hurricane Center continues to highlight
an area for potential tropical development over the northwestern
Caribbean next week (20 percent chance of cyclone formation in 7
days). However, it is still way too early and models are still in
far-reaching disagreement regarding the general synoptic pattern,
much less the potential for tropical development, beyond days
6-7.

&&

.MARINE...
Issued at 410 PM EDT Wed Sep 18 2024

Now-Tonight...Light onshore flow turns offshore tonight. Seas
remain generally favorable, around 3-4 ft, outside of any
isolated/scattered lightning storms that push offshore this
evening.

Thursday-Sunday...Another day of winds becoming onshore around 10
kt Thursday afternoon, with isolated/scattered showers possible by
the late afternoon and evening (mainly south of Cape Canaveral).
Seas decrease further, around 2-4 ft. A surface front traverses
the local waters on Friday, settling across south Florida and the
Florida Straits this weekend. Northeast winds increase
persistently each day, especially in the afternoon hours, gusting
as high as 15-20 kt by Sunday. Seas gradually build Saturday into
Sunday as a result, up to 5 ft offshore by Sunday afternoon/night.

&&

.HYDROLOGY...
Issued at 410 PM EDT Wed Sep 18 2024

The Saint Johns River at Astor is forecast to remain in Moderate
Flood stage into the upcoming weekend. The potential exists for
small additional rises if locally heavy rainfall develops over the
river basin. Farther upstream, a slow and steady rise of the Saint
Johns at Deland and Sanford is expected to continue, so interests
along the river should monitor for future forecast updates.

&&

.AVIATION...
(18Z TAFs)
Issued at 206 PM EDT Wed Sep 18 2024

VFR conditions are forecast outside of showers/storms. Scattered to
numerous showers and lightning storms are forecast into the PM. VCTS
begins between 19-21Z with TEMPO TSRA groups between the 21-01Z timeframe
(except for KLEE). Isolated east moving storms will be capable of wind
gusts up to 40-50mph over ECFL. Light and variable winds are forecast
to gradually become onshore into the afternoons/evenings at 5-10kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  73  90  73  89 /  50  30  10  20
MCO  74  92  73  91 /  30  50  10  30
MLB  74  90  75  88 /  60  40  40  30
VRB  73  90  73  89 /  60  50  40  40
LEE  74  90  73  90 /  20  40  10  20
SFB  73  91  73  90 /  30  50  10  30
ORL  75  92  75  91 /  30  50  10  30
FPR  73  90  73  89 /  60  60  40  50

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Coastal Flood Advisory until 2 PM EDT Friday for FLZ141-154-159-
     164-347-447-647-747.

AM...None.
&&

$$

DISCUSSION...Schaper
AVIATION...Fehling