969
FXUS62 KMLB 210644
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
244 AM EDT Sat Sep 21 2024

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

.DISCUSSION...
Issued at 244 AM EDT Sat Sep 21 2024

KEY MESSAGES:

- Onshore winds and a northeasterly swell will promote a Moderate
  to High Risk of life-threatening rip currents at Central
  Florida`s Atlantic beaches.

- Minor coastal flooding remains possible, particularly during the
  late morning high tides through this weekend. Low-lying streets,
  yards, and docks along the barrier islands and Intracoastal
  Waterway may experience minor flooding.

- There is a medium chance (60%) for tropical development in the
  northwest Caribbean or southern Gulf of Mexico next week. It is
  too early to determine if and what impacts this may bring to
  East Central Florida. Continue to monitor the forecast for
  updates.

              ----------Synoptic Overview----------

A weakening mid-level trough resides over the Eastern U.S. this
morning. Lingering pockets of vorticity will stream overhead while
the trough dissipates this weekend. Upper-level high pressure
remains over the Ark-La-Tex region, but a cut-off low over Arizona
has started to nudge it eastward. Over the next few days, this
ridge will become anchored very close to Florida as multiple
shortwaves form a trough across the Upper Midwest. Beneath the
upper high, H5 temperatures are expected to approach the 99th
percentile of climatology.

At the surface, high pressure will slowly move from the Appalachians
this weekend into the Atlantic early next week, reinforcing onshore
NE to E winds across the Florida Peninsula. Total atmospheric
moisture will remain near to just below normal through this weekend
before dropping further below average early next week. The marine
influence keeps temperatures very close to normal for the opening
days of autumn.

Ensemble guidance indicates deep tropical moisture and convection
will consolidate early this week over the northwestern Caribbean
Sea. By Wednesday, ensemble-averaged negative pressure anomalies
are generally centered just offshore of the Yucatan Peninsula.
Those negative pressure anomalies and associated tropical moisture
are forecast to lift into the Gulf of Mexico late next week.
There is a medium chance of tropical development with this
feature.

             -------Sensible Weather & Impacts-------

Through The Weekend...

Seasonable moisture values remain over the state, however much of
that moisture resides in the lowest 10 KFT. Weak ripples of
vorticity streaming off the Atlantic in the northeast flow will be
enough to spark widely scattered (30-40%) low-topped showers and a
few storms, with some of this activity persisting overnight along
the coast. High temps reach the upper 80s to around 90F, with lows
in the low/mid 70s.

Northeast winds will become breezy at times, with gusts up to 20
mph, especially near the coastline. Beach-goers should expect surf
of 3-4 FT and a moderate to high risk of rip currents, especially
surrounding low tide in the afternoon and early evening.
Additionally, minor coastal flooding remains a concern during high
tide. The highest water levels are forecast in the late morning
hours with a secondary peak in the late evening. Remember never to
drive through salt water!

Autumn begins at 8:43 am ET on Sunday.

Monday-Wednesday...

Quiet early autumn weather as we head back to work and school.
Deep-layer ridging continues to build as drier air drifts
overhead. H5 T`s soar to a very suppressive -3 or -4C as H5
heights reach 591 dam in the grand ensemble mean by early
Wednesday.

Bottom line, shower/storm chances lessen to 10-20% from Orlando
northward and 20-30% to the south each day. Surface high pressure
drifting into the Atlantic will deliver breezy easterly winds.
Expect partly to mostly sunny skies with highs in the upper 80s to
low 90s.

Thursday & Beyond...

The weather during this timeframe will be almost entirely dictated
by the ultimate evolution and movement of lower pressures and rich
tropical moisture rising from the Caribbean into the Gulf. Most
ensemble members show this disturbance making it into the southern
Gulf of Mexico by Wednesday or Thursday. After that time,
significant uncertainty remains, which is expected at this stage.
Guidance on potential tropical development may take several days to
resolve, due to the initial absence of a trackable feature and the
evolving upper air pattern over North America. The depth and
position of a trough over the Midwest still look to be the ultimate
variables in when and whether this disturbance gets a kick
north/northeastward.

The National Hurricane Center has increased the chance of tropical
development in the southern Gulf to 60%. It remains too early to
determine local impacts. We continue to advertise an increase in
rain/storm chances (40-60%) from Thursday into next weekend,
which is supported by the expected uptick in tropical moisture
over the state.

We are now in peak hurricane season. Check weather.gov/mlb and
hurricanes.gov for the latest updates, and take the time to check
on your hurricane preparedness kits and plans.

&&

.MARINE...
Issued at 244 AM EDT Sat Sep 21 2024

This Weekend... High pressure holds over the Southeast U.S.,
ensuring northeast winds 8-15 KT. Nearshore seas 3-4 FT building to
4-5 FT in the Gulf Stream beyond 20 nm. Scattered showers and
isolated lightning storms will persist over the next couple days.

Monday-Wednesday... Occasionally poor boating conditions. High
pressure pushes into the W Atlantic, allowing winds to turn from ENE
to E 10-15 KT. Seas 3-5 FT, except up to 6 FT well offshore. Rain
shower coverage becomes more isolated late Monday through mid-week.

&&

.AVIATION...
(06Z TAFs)
Issued at 131 AM EDT Sat Sep 21 2024

MVFR conditions occurring at LEE due to BR will likely continue
through the overnight hours. Otherwise, VFR conditions prevailing.
Showers will continue to occasionally stream onshore into coastal
areas, at times approaching coastal terminals. VCSH has been
included into the early afternoon (18Z) in these locations.
Isolated to widely scattered showers will then progress inland
along onshore flow, diminishing by around 0Z. Showers will then be
possible once again overnight along the coast. Breezy onshore
winds today will increase to around 12kts, with gusts around 20kts
this afternoon, especially for coastal terminals. Winds will
diminish this evening.

&&

.HYDROLOGY...
Issued at 244 AM EDT Sat Sep 21 2024

The Saint Johns River at Astor is forecast to remain in Moderate
Flood stage through at least the weekend. Farther upstream, the
Saint Johns at Deland and Sanford will remain near or slightly above
Action Stage.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  87  75  89  75 /  30  20  30  10
MCO  89  74  91  74 /  30  10  30  10
MLB  88  76  89  76 /  40  20  30  20
VRB  88  74  89  75 /  40  20  30  30
LEE  90  73  91  73 /  20   0  20   0
SFB  88  74  89  73 /  30  10  30   0
ORL  90  75  91  75 /  30  10  30   0
FPR  88  74  89  75 /  40  20  40  30

&&

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

AM...None.
&&

$$

DISCUSSION...Heil
AVIATION...Leahy