Sebastian, Florida Weather Forecast Discussion

546
FXUS62 KMLB 100654
AFDMLB
Area Forecast Discussion
National Weather Service Melbourne FL
254 AM EDT Wed Sep 10 2025
...New KEY MESSAGES, DISCUSSION, MARINE...
.KEY MESSAGES...
Issued at 254 AM EDT Wed Sep 10 2025
- Wet and unsettled conditions persist through at least Thursday
  as a lingering front and deep moisture enhances coverage of
  afternoon showers and lightning storms.
- A low threat for locally heavy rainfall and mostly minor
  flooding will continue this week, as multiple rounds of showers
  and storms are forecast.
- Temperatures are forecast to be near to slightly below normal
  through this week, with highs generally in the mid-upper 80s.
&&
.DISCUSSION...
Issued at 254 AM EDT Wed Sep 10 2025
Current-Thursday...Most of the convection early this morning remains
over the local coastal waters, but still cannot rule out ISOLD re-
development almost anywhere - though most likely near the Volusia
coast due to the very moist airmass, various boundaries, and
impulses aloft. Warm and muggy conditions continue with generally
light winds, but a bit stronger along the Volusia coast where
onshore winds persist on the north side of a quasi-stationary
frontal boundary.
The weak front is forecast to transition slowly southward across
central FL during the day finally pushing across Lake Okeechobee Thu
afternoon. The very moist airmass remains in place with PWATs 2.00-
2.40" today, but a tighter moisture gradient on Thu with values
falling to 1.60" Thu afternoon north/west of I-4 and remaining
fairly moist southward in excess of 2.00". Mid-level (H500) temps
remain consistent between -5.5C to -6.5C today cooling slightly into
Thu (-6.5C to -7.5C). Shortwave impulses will again traverse the
FL peninsula embedded within the SWRLY flow aloft aiding
convection. We continue a fairly high coverage of showers and
lightning storms (60- 80pct) today, lowering to 30-50% north/west
of I-4 on Thu and at least 50-70% southward. Highest coverage and
greatest storm intensity will typically be during the afternoon
and evening hours. Overnight and morning convection will be
closely associated with the front`s proximity during this time.
Storm steering flow continues to remain weak.
Locally heavy rainfall will remain the primary threat, esp for
areas that see multiple rounds and for those locales that have
already seen multiple days of torrential downpours. Daily
accumulations of 2-4" (ISOLD higher) could lead to minor/nuisance
flooding concerns. This will also be problematic for
streams/rivers as they approach and possibly exceed bankfull. A
Marginal Risk for excessive rainfall will continue, though a
Slight Risk for excessive rainfall will creep northward from south
FL into Okeechobee County and the Treasure Coast for Thu.
Additional threats from the strongest storms include occasional to
frequent lightning strikes and gusty winds up to around 45 mph.
The latest HRRR targeting Brevard County overnight for some
potential heavy precip amounts, so we will see if consistency in
future model runs continue.
Highs will be near to slightly below normal, mostly in the M-U80s to
around 90F. A N/NE wind component will be observed north of the
boundary and could be breezy at times due to local sea breeze
enhancement. A more WRLY to variable component will exist south of
the boundary.
A persistent northeast swell will promote numerous, strong, life-
threatening rip currents at area beaches, esp the Volusia, Brevard,
and Indian River coasts. Rough surf will also continue. Entering the
surf is strongly discouraged!
Fri-Wed...Medium range models show an upper trough, initially strung
across the Eastern Seaboard through the FL Panhandle, forecast to
slide southward across the FL peninsula this weekend. The latest GFS
shows a closed (mid-level) low developing over Florida - slowly
taking this feature northward into Georgia by mid next week. The
ECMWF develops a closed (mid-level) low off of the Carolina
coast, then taking this feature northward along the mid Atlc and
northeast U.S. coast thru the same timeframe. A weak surface low
(reflection) is likely to develop from all of this somewhere off
of northeast FL to the Carolinas. Whatever transpires, drier air
will slowly work southward down the peninsula this weekend and
early next week.
For PoPs on Fri, we carry 20-40pct from Lake County, across I-4 and
through Volusia County, with 50-70pct southward toward Lake Okee and
the Treasure Coast. With a likely tight moisture gradient on Fri,
there will still be a Marginal Risk for excessive rainfall south of
the Cape and a Slight Risk for excessive rainfall across Martin
County. Trying to keep with continuity further into the extended
expect generally 30-40pct mainly diurnal convective chances from Sat-
Wed - though 50pct for Okeechobee County & the Treasure Coast on
Wed. Afternoon highs consistent in the M-U80s with lows in the L-
M70s - though could see some U60s across normally cooler rural
locations over the interior. Generally an onshore wind component
through the weekend, with a bit more uncertainty into next week
surrounding placement and strength of certain low/upper-level
weather features.
&&
.MARINE...
Issued at 254 AM EDT Wed Sep 10 2025
Today-Tonight...Still witnessing elevated seas (6.2-6.6 ft) at
buoy 41070 early this morning. For now, will keep Small Craft
Advisory (SCA) going for the Volusia waters (0-60nm) and extend
slightly thru 12Z/8AM this morning. Models continue to suggest 4-6
ft seas over the offshore waters into this evening, so will
continue Cautionary Statements here as well. For the remainder of
the waters mainly 3-5 ft seas. A weak frontal boundary north of
the Cape will continue to very slowly push southward into Brevard
County late today and tonight. This will continue to provide focus
for continued above normal rain and lightning storm chances.
North of the front winds will be more N/NE and could increase up
to around 15 kts at times. Further south, more westerly/variable
flow at 5-10 kts.
Thu-Sun...The boundary will only drift slowly southward thru Thu
(southern/Treasure Coast waters), but then get a kick further south
into south FL Fri into the weekend with the approach of an upper
trough. Precip chances remain high thru Thu (and southern waters
on Fri), but begin to diminish slowly from north to south Fri
into the weekend as drier air gradually moves in. Wind directional
component will also transition to NNE/NE late week into the
weekend. Wind speeds will begin to increase, esp north of the Cape
Fri afternoon thru the weekend and may approach Cautionary levels
here (15-20 kts) at times. Seas 3-5 ft but will approach 6 ft,
again, Fri night into Sun.
&&
.AVIATION...
(06Z TAFs)
Issued at 120 AM EDT Wed Sep 10 2025
MVFR/IFR CIGs setting up across the interior terminals, so added
in TEMPOs at MCO, ISM, SFB, and LEE through at least 10Z, with
extensions in time likely needed. Lowered CIGs remaining away from
the coastal terminals for now, but will monitor closely. Another
active weather day is forecast within vicinity of the terminals,
with VCSH after 15Z across the interior terminals and TIX
northward, with VCTS after 18Z at all terminals. Too early to add
in TEMPOs for TSRA, but best first guess would be starting as
early as 19Z across the interior terminals. Will monitor guidance
trends for the next forecast package. Lingering VCSH through the
overnight hours at DAB, TIX, and MLB, with mostly dry conditions
elsewhere beyond 03Z. Winds become gusty up to 20 knots out of
the NE this afternoon, with winds becoming lighter and even
variable at times through the overnight hours. Another night of
lowered CIGs seems possible late tonight into tomorrow, but
confidence remains low.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB  85  75  85  74 /  60  40  40  20
MCO  89  75  87  74 /  80  30  60  20
MLB  87  76  87  75 /  70  50  70  50
VRB  90  74  88  74 /  80  50  70  50
LEE  87  73  87  71 /  60  20  30  10
SFB  87  74  87  72 /  70  30  50  20
ORL  87  75  87  73 /  80  30  50  20
FPR  90  73  88  72 /  80  50  70  50
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 8 AM EDT this morning for AMZ550-570.
&&
$$
DISCUSSION...Sedlock
AVIATION...Tollefsen

NWS MLB Office Area Forecast Discussion