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560
FXUS62 KILM 180755
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
355 AM EDT Wed Sep 18 2024

.SYNOPSIS...
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Weakening low pressure will bring a couple days of unsettled
weather today and Thursday. Slightly cooler and drier weather
will accompany persistent north-northeasterly winds over the
weekend while high pressure maintains control.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Messy pattern today with the remains of a weak front draped across
the forecast area and weak afternoon sea breeze developing. A 5h low
over the western Carolinas, all that`s left of the system that
aspired to be tropical but couldn`t quite make it, will slowly move
east-northeast today. Deeper moisture and modest height falls
associated with the low coupled with weak low level convergence from
the front/sea breeze, will lead to afternoon convection. Best
chances will be across SC portions of the forecast area , under the
upper low and coincident with the bulk of the deep moisture. Some of
this activity will spread east, but by the time low pressure aloft
and deeper moisture moves over the southeastern NC coast the low
level instability will be waning. SBCAPE values this afternoon
across northeast SC approach 1000 J/kg but across southeast NC
SBCAPE will struggle to hit 500 J/kg. By the time the upper low
begins to exert some influence over the NC portion of the forecast
area those values will be trending down. The result will be high
chances for showers and isolated thunderstorms across inland SC with
pop decreasing to the east and northeast. Temperatures a degree or
two warmer than Tue on the back of some weak warm advection and more
sunshine. Lows will end up near to slightly above climo due to
increased cloud cover/debris cloud.
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&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
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The aforementioned mid-level low should open up into the broader
troughing over the Eastern Seaboard early in the period with its
associated vorticity weakening and breaking up into lobes as it
tracks eastward. With the trough axis nearby or overhead on
Thursday, cooler mid-level temperatures will result in slightly
steeper lapse rates and should yield modest instability during
the afternoon (e.g., 500-1000 J/kg MLCAPE, up to around 1500
J/kg of SBCAPE) assuming that morning cloud cover is not too
extensive. Ultimately, it appears that scattered showers and
isolated thunderstorms will be the story during the day with
some focus along the sea breeze. This is expected despite a
light northerly flow behind a weak front that should push
offshore prior to sunrise on Thursday. With PWATs holding around
1.5-1.75" behind the front, brief heavy rain will be possible
with the strongest cores. Highs should reach the low 80s.

During the evening and overnight, the loss of daytime heating
should result in the dissipation of most or all activity by
midnight. Light or calm winds across most of the area may yield
fog or low clouds depending on how clear skies become overnight.
Drier air coming in aloft should help to dissipate any mid-level
clouds, but low stratus may hang around through much of the
night. Lows should fall into the mid 60s away from the
immediate coast.
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&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
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With mid-level troughing shifting eastward, increasing dry air
and subsidence aloft through much of the weekend should keep
rain chances too low to mention. Meanwhile, a surface is
expected to meander off the coast of the upper Mid-Atlantic
before eventually shifting away late in the weekend. While this
should remain far enough away to preclude any sensible weather
impacts, this will need to be monitored. Otherwise, expect this
low to maintain north-northeasterly winds through the weekend,
keeping dew points at manageable levels generally in the
mid-60s. Temps will hold near- to slightly below normal for this
time of year with highs in the low-mid 80s and lows in the low-
mid 60s.

Early next week, confidence decreases as the pattern evolves.
Overall, mid-level ridging should hold in place while surface
high pressure produces another surface wedge east of the
Appalachians. The end result should be dry conditions and
temperatures near or just below seasonal levels. However,
northwesterly flow on the front side of the ridge may bring
debris clouds or rain chances via shortwave impulses, so this
will need to monitored.
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&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
Generally VFR with brief periods of MVFR/IFR possible.
Increasing cloud cover associated with the low pressure aloft
over the western Carolinas is making an already difficult fog
forecast even more troublesome. Latest trends on satellite show
this cloud cover expanding as it rotates north over most of the
terminals. The increase in cloud cover will arrive 07-09Z
across SC and a bit later across NC. Have scaled back on
fog/visibility restrictions counting on the clouds to limit fog
development. Confidence is on the low side though, as larger
breaks in cloud cover or clouds dissipating would lead to higher
potential for IFR/MVFR. Widespread VFR shortly after daybreak.

Diurnal convection will be a concern this afternoon and
evening, especially for inland terminals. Storms will generally
be diurnal in nature with coverage dropping off rapidly
approaching 00Z. Depending on rain/debris cloud tonight MVFR/IFR
fog is possible around the end of the TAF period.

Extended Outlook...Afternoon MVFR possible Thursday with
morning MVFR/IFR possible Thursday and Friday mornings.

&&

.MARINE...
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Through Tonight...
Light offshore flow this morning will become onshore around midday
in response to development of weak sea breeze. Away from the
immediate coast wind directions will be a little more variable, but
speeds will be around 5 kt so not much concern. Seas around 2 ft
with an occasional 3 ft given the weak gradient and light winds. An
easterly swell will be the dominant wave with nary a wind wave to be
found.

Thursday through Sunday...
Predominantly light north to northeasterly flow at around 10 kts
or less will be the story through the period as surface low
pressure meanders off the upper Mid-Atlantic coast. As this low
departs, we may see a tighter pressure gradient mainly on Sunday
produce north winds of 10-15 kts, but this will depend on its
track. Easterly swells of 2-3 ft at 9-10 sec will dominate the
wave spectrum while 1-2 ft wind waves at 3-4 sec become active
each afternoon from Friday onward.
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&&

.TIDES/COASTAL FLOODING...
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High astronomical tides and a bit of lingering swell from the
prolonged onshore winds will lead to coastal flooding with the
morning high tides across the forecast area. Water levels should
remain in the minor category and another round of advisories is
expected with this evening`s high tides.

Other - Rip Currents:
Continued improving surf conditions affecting all beaches for
Wed. A slowly decaying easterly swell at 9+ second periods will
affect local beaches. However, for the Pender and New Hanover
County Beaches, the surf will remain conducive for a Moderate
rip Current Risk for Wed, especially in that 4 hr window
centered around low tide.
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&&

.ILM WATCHES/WARNINGS/ADVISORIES...
NC...Coastal Flood Advisory from 6 AM to 10 AM EDT this morning for
     NCZ106-108-110.
     Coastal Flood Advisory from 8 AM this morning to 1 PM EDT this
     afternoon for NCZ107.
SC...Coastal Flood Advisory from 7 AM to 10 AM EDT this morning for
     SCZ054-056.
MARINE...None.

&&

$$

SYNOPSIS...ILM
NEAR TERM...III
SHORT TERM...ABW
LONG TERM...ABW
AVIATION...III
MARINE...III/ABW
TIDES/COASTAL FLOODING...ILM