467
FXUS62 KMLB 151450
AFDMLB

Area Forecast Discussion
National Weather Service Melbourne FL
1050 AM EDT Sun Sep 15 2024

...New UPDATE...

.UPDATE...
Issued at 1050 AM EDT Sun Sep 15 2024

Morning sounding from the Cape at 10Z had a PW value of 1.8", but
this will steadily decrease through the day as 12Z sounding at TBW
shows PW around 1.4", and this drier air will only continue to
spread eastward through the day. Model guidance shows PW values
ranging as low 1.4-1.5" across much of the area this afternoon,
with slightly higher values up to 1.6-1.8" across northern
Lake/Volusia counties and the southern Treasure Coast. Isolated to
scattered showers and storms will still be possible into the
afternoon and evening, but coverage will be lower, with rain
chances only around 20-30 percent for much of east central FL up
to 40 percent north of Sanford and across Martin County where
greatest moisture will continue to reside. Main storm threats
today will include lightning strikes, gusty winds locally up to
around 40 mph, and heavy downpours.

Skies will be a mix of partly to mostly cloudy with diurnal cu
development and higher cloud cover that will continue to spread
southeast across central FL. Highs will reach the upper 80s and
low 90s and while dewpoints drop a tad today, there will still be
sufficient humidity to produce peak heat index values up to
100-107F. Highest of these values will continue across southern
Okeechobee County and the Treasure Coast.

&&

.PREVIOUS DISCUSSION...
Issued at 246 AM EDT Sun Sep 15 2024

...Patchy, locally dense, fog will linger into mid morning...

...Deteriorating boating and surf conditions beginning today into
early next week...

...Afternoon highs in the upper 80s to low 90s with a Moderate Heat
Risk expected into early next week...

...Saint Johns River at Astor forecast to remain in Moderate Flood
through mid next week...

Current-Tonight... Warm & humid conditions prevail with temps and
dewpoints in the 70s early this morning. GOES-16 ECONUS Total PWAT
imagery shows much drier air over the eastern GoMex pushing onto the
WCFL coast. KMLB 88D shows scattered showers and isolated lightning
storms over the local coastal waters. The HRRR forecasts some of
this activity to sneak onto the Volusia and Brevard coasts through
early morning. Occasional lightning and brief downpours the main
threats here. Surface winds over land remain light/variable to calm.
With ample moisture at the surface from recent widespread heavy
rainfall, near calm winds, and clearing skies, we are likely to
observe, again, areas of low stratus clouds and patchy fog (locally
dense) across ECFL. The models are not too keen to depict this, but
this does seem feasible given what we witnessed in portions of ECFL
Sat morning. Any low stratus or fog should quickly burn off thru mid
morning as the sun comes up.

A mid-level low continues to spin across the Mississippi Valley with
influence extending across the rest of the Deep South to include the
southeast U.S. and north FL. This feature will continue to slowly
weaken and retrograde a bit during this period. Another mid-level
low offshore of the South Carolina coast will continue to strengthen
and move NW onto land later tonight. The associated weak surface
reflection will also strengthen slowly and follow suit toward the
South Carolina coast. It is this non-tropical area of low pressure
that may gradually acquire subtropical or tropical characteristics
(50pct) over the next couple of days.

H500 temps are forecast to range from -5.5C to -6.5C, but may cool
an additional couple of degrees by sunrise Mon morning. This as
subtle weak mid-level impulses embedded in the WSW flow aloft
continue to traverse north FL. PWATs are forecast to decrease quite
a bit as drier air pushes eastward across the peninsula from the
GoMex, with values 1.35-1.50 inches across the center of the state
and 1.50-1.80 inches across our northern/southern coverage warning
areas. Light/variable morning winds remain untouched into early
afternoon, but expect an onshore (NNE/NE) wind component to develop
along the coast this afternoon and slowly translate inland. The WCSB
will again be the dominant of the two sea breezes and move across
the peninsula through the afternoon. Expect an eventual collision
across the eastern peninsula late in the day or early evening.

With the drier air pushing into ECFL, models have trended quite a
bit lower with PoPs for today; 30pct I-4 northward and 30-40pct
Okeechobee and the Treasure Coast with 20pct in between. Storm
motion remains WRLY and a bit stronger today 10-15 mph. Highest
coverage likely to be realized during the mid-late afternoon and
early evening period. Primary storm impacts include lightning
strikes, gusty winds locally up to around 40 mph, and torrential
downpours. Activity will diminish thru mid evening.

Afternoon highs in the U80s to L90s with peak heat indices this
afternoon 102-107F. Not keen on a Heat Advisory for today, though
conditions still remain very warm and humid - though perhaps a
little drier than recent days. A Moderate Heat Risk will exist
across ECFL today. It remains recommended to take frequent breaks
from the heat and stay hydrated, especially if spending extended
periods of time outdoors during the afternoon. Conditions humid
overnight with lows in the L-M70s, except a little higher along the
immediate Space/Treasure coasts.

There will be a HIGH risk for life-threatening rip currents along
the Volusia beaches today and on Monday, as incoming NERLY long
period swells affect area beaches. While a Moderate risk for
dangerous rip currents exists southward today, there is a chance
this gets bumped up to HIGH for Monday and beyond.

Mon-Sat...Still watching the weak area of low pressure off of the
South Carolina coast to see if it develops (50pct) further ahead of
moving NW and inland across the Carolinas and across the mid Atlc
States. Drier air still forecast to move into the central peninsula
early this week and remain in place (mostly below 1.80 inches) for
much of the extended. While lower PWATs are expected, a daily sea
breeze along the east coast is expected to develop under a weak
pressure gradient, with inland movement of this feature expected
further westward as we head later into the week. Storm steering flow
remains of a SW/W component with highest coverage of storms (40-
50pct - perhaps locally higher) forecast across the eastern
peninsula each afternoon/early evening.

There is some cooling forecast at H500 (-7C to -8C) which could aid
destabilization each day. Rather a messy/troughy pattern in the mid-
levels will exist from the mid Atlc thru the southeast U.S. and FL
peninsula during this period and we will see periodic shortwave
impulses/troughs traversing the area.

Afternoon highs in the U80s to L90s each day, with overnight mins in
the L-M70s, except U70s along the immediate Space/Treasure coasts.

&&

.AVIATION...
(12Z TAFs)
Issued at 733 AM EDT Sun Sep 15 2024

Fog prevails at LEE through 13Z before gradually lifting. MVFR CIG
TEMPOs at ISM/MCO/TIX where periods of stratus have been observed.
North to northeast winds become variable at times throughout the
day, generally remaining 10 kts or less. VCTS at all terminals
this afternoon. Overall convective coverage remains low compared
to yesterday, and there is no need to include TSRA TEMPOs with
this TAF package.

&&

.MARINE...
Issued at 246 AM EDT Sun Sep 15 2024

Today thru Thu...Drier air will work across the peninsula today
lasting into next week, though scattered showers and lightning
storms will remain in the forecast. Mariners are still reminded to
keep an eye to the sky westward as the storm steering flow will
continue to be WRLY, which will bring offshore moving showers and
storms across the local waters. There should be ECSB formation
each day as light onshore winds develop each afternoon.

Winds speeds AOB 15 kts (outside of convection) through next
week. Seas 2-4 ft near shore and 4-5 ft offshore will continue to
build due to increasing long period NERLY swells. Wave heights
will reach 4-5 near shore (6ft Cape northward) and 5-8 ft offshore
and Gulf Stream by early evening. These values will continue into
Mon night before a gradual subsiding Mon overnight into Tue where
values will fall to 3-4 ft near shore and 4-5 ft near shore by
early Tue evening. Seas continue to subside thru mid-week (3-4
ft).

Poor to hazardous seas will be observed for most marine legs
this afternoon into early next week. As such, a Small Craft
Advisory (SCA) goes into effect for offshore marine legs (north of
Sebastian Inlet) at 2PM/18Z, then further south across the
offshore Treasure Coast waters at 8pm/00Z. Small craft should
Exercise Caution elsewhere this afternoon and tonight. Will allow
later shifts to monitor and add any near shore marine zones as
appropriate to the SCA.

&&

.PRELIMINARY POINT TEMPS/POPS...
DAB  88  74  88  73 /  30  20  50  10
MCO  91  75  90  75 /  30  10  50  10
MLB  90  75  90  75 /  20  10  30  30
VRB  91  74  90  75 /  30  10  40  30
LEE  90  74  89  74 /  30  10  50  10
SFB  89  74  89  74 /  30  10  50  10
ORL  91  76  90  75 /  30  10  50  10
FPR  91  74  90  75 /  30  10  40  30

&&

.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory from 2 PM this afternoon to 10 PM EDT
     Monday for AMZ570-572.

     Small Craft Advisory from 8 PM this evening to 10 PM EDT Monday
     for AMZ575.

&&

$$

UPDATE...Weitlich
AVIATION...Law