829
FXUS62 KILM 231037
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
637 AM EDT Tue Jul 23 2024

.SYNOPSIS...
Occasional showers and thunderstorms, some with heavy rain,
will continue through the remainder of the week as southerly
winds bring tropical moisture northward. A weak front could
stall near the area this weekend.

&&

.UPDATE...
No significant changes with the 7 AM EDT update.

&&

.NEAR TERM /THROUGH TONIGHT/...
Weak ridging over the western Atlantic will build westward today.
This minimal subsidence should reduce some of the widespread
coverage of showers and storms seen in previous days. Less
convection and cloud cover will allow temperatures to reach the
lower 90s and upper 80s along the coast.

A tropical air mass remains over the area and instability during the
afternoon should produce isolated to scattered convection again,
despite the weak ridging. A weak sea breeze will see shower activity
develop during the early afternoon near the coast and push inland
through the afternoon. Outflows should initiate additional storms
inland with convection along the Piedmont trough feeding from the
added convergence.

PoPs reflect a 60% chance this afternoon, mainly west of I-95. There
is some uncertainty in where an axis of heavy rain develops this
afternoon. Lift and aforementioned ridging suggest this axis could
develop farther west (outside of the CWA), keeping inland convection
scattered. If this axis develops near the I-95 corridor, heavy rain
and flooding will be possible in training storms.

A similar expectation of PoP this evening with areas behind the sea
breeze staying dry while elevated instability sustains any developed
convection. Onshore winds could bring another round of convection
and showers during the late evening where convergence is maximized.
Late nights showers and storms may impact the coastal communities
around sunrise. Lows in the mid and upper 70s with low 80s near the
coast.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
The subtropical ridge will be centered just north of Bermuda
Wednesday and Thursday and should become very strong with 500
mb heights approaching 600 dam. The surface high centered just
downstream of the upper ridge will remain expansive through
the first half of Thursday covering most of the western
Atlantic with its clockwise flow. Tropical moisture pulled from
the northern Caribbean will flow across the Carolinas by way of
the Bahamas, maintaining a sticky low level airmass with
dewpoints well into the 70s.

A mid and upper level trough extending from the Great Lakes down
to Louisiana will bring Gulf moisture streaming in aloft on
southwest winds. This flow of Gulf plus Atlantic moisture
should keep precipitable water values very high in the 2.2 to
2.5 inch range, about half an inch above the daily median value
and approaching the daily observed max values at Charleston.

Wednesday and Thursday may see the same general pattern with
showers and thunderstorm coverage: morning convection across
the coastal waters is expected to spread onshore after sunrise,
then will spread farther inland during the afternoon hours with
coastal and offshore locations drying out behind the seabreeze
front. Forecast PoPs are highest inland (70-80 percent) and
about 20 percent lower along the coast. Slightly veered but
generally southwesterly flow should favor slow moving
thunderstorm clusters producing locally heavy rainfall.

By Friday, the Great Lakes upper trough will shift east across
New England. This will turn our steering flow more westerly with
the timing and coverage of showers and storms expected to
become more diurnally focused even along the coast. A surface
cold front pushed southward by the New England trough should
arrive Friday night into Saturday, maintaining a risk for
showers and thunderstorms.

Temperatures through the period should be modulated by
convective coverage and cloud cover. The warmest daytime highs
are expected Wednesday (lower 90s) but should remain generally
in the 80s the remainder of the week. Overnight lows should fall
into the 70s.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
The surface cold front is expected to slip south across our
portion of the Carolinas Saturday, stalling across southern
South Carolina for the remainder of the weekend. Surface winds
turning northeast to easterly behind the front won`t allow
dewpoints to fall tremendously but it`s possible we could see
some sub-70 dewpoints show up Sunday and Monday afternoons,
especially away from the coast. The airmass aloft does appear it
will dry out significantly early next week with precipitable
water values shown on the GFS to fall below 1.25 inches, very
close to the 10th percentile climo value for this time of the
year.

Precip potential will remain fairly good Saturday as convergence
along the front should support scattered showers and storms. By
Sunday and Monday drier and more stable conditions should
develop and the risk of showers should drop below 20 percent for
all but perhaps the southern portion of the Grand Strand.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
VFR this morning with some isolated VCSH along the coast before
noon. Onshore flow will assist a developing sea breeze early
this afternoon. Similar day today as yesterday. Showers and
storms likely to develop this afternoon along the sea breeze and
push inland through the afternoon. Parallel flow aloft and deep
moisture likely to create a persistent convective band
somewhere across the central Carolinas. Confidence is low
regarding where this will set up, but have included the
potential in the TAF at this stage. Rain ending overnight inland
with shower chances transitioning toward the coast. Possibility
of IFR/MVFR low clouds inland tonight.

Extended Outlook...Potential for IFR/MVFR with showers and
thunderstorms each day.

&&

.MARINE...
Through Tonight...No changes from the previous forecast. South
winds at 10-15 knots during the day weaken slightly and become
southwesterly overnight. Gusts up to 20 knots during the day as a
weak sea breeze develops. SE swell continues at 2-3 feet at 9
seconds.

Wednesday through Saturday night...Bermuda High Pressure will
continue to bring south-southwest winds across the Carolina
coastal waters much of this week. Coming along for the ride will
be deep tropical moisture from the Bahamas which should
maintain occasional waves of showers and thunderstorms. For
Wednesday and Thursday the coverage of storms should be highest
during the morning hours, becoming more widely scattered during
the afternoons and evenings.

However by Friday storm movement should become more west to
east as a dip develops in the jet stream across the northeastern
U.S. Waves of showers and thunderstorms Friday should persist
through the day and into Friday night as a cold front, pushed
south by the same dip in the jet stream, approaches from the
north. The front should move south across our area Saturday with
winds shifting to the northeast Saturday night.

The primary wave group much of this week should be a
southeasterly "Bermuda" swell at 8-9 seconds period. Southerly
wind chop should be most prevalent Wednesday through Thursday,
diminishing Friday as the front approaches from the north.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
NC...None.
SC...None.
MARINE...None.

&&

$$

SYNOPSIS...TRA
UPDATE...21
NEAR TERM...21
SHORT TERM...TRA
LONG TERM...TRA
AVIATION...21
MARINE...TRA/21