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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 200738
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
338 AM EDT Mon Aug 20 2018

.SYNOPSIS...
High pressure offshore will maintain warm and humid weather
today, with isolated showers and thunderstorms. Rain chances
will increase ahead of a cold front Tuesday into Wednesday.
An early hint of fall will arrive late week, as Canadian high
pressure drops in behind the front, bringing drying and slight
cooling, Friday into the early weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 338 AM Monday...Convection and coverage thereof continues
to underperform with the synoptic scenario. The axis of
concentrated activity this morning is to our north associated
with a couple of shortwaves embedded in the generally westerly
flow aloft. For the next few hours I have dramatically decreased
pops as there will inevitably be some NVA in the wake of the
activity. As for later today, somewhat of a repeat of the past
couple of days with an agonizing struggle for convection. The
GFS paints a wide swath of showers later this morning but this
may be more of a stratus layer that persisted inland for a while
Sunday. The GFS has been way to aggressive with pops/qpf
anyhow. Overall still have slight to low chance pops along the
coast to chance northern and inland areas. Some indication of
diurnal activity early Tuesday but based on the past couple of
nights and really all periods confidence is low. Essentially no
change from previous days and nights for the thermal forecast.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 338 AM Monday...Warm air advection encompasses nearly all
this time period, with a frontal passage prior to daybreak
Thursday, and GFS/ECMWF surface agreement on timing, with cool
air advection poised to filter in Thursday. Precipitable water
analysis shows a peak in vapor content late Tuesday before a
decreasing trend, as the river of high PWATs edges offshore. As
such, column drying will already be underway well before frontal
passage, with drying down to 700 mb Wednesday. A short wave and
jet energy to the north late Wednesday, will sustain shower
chances into evening, driving frontal passage through the area
prior to sunrise Thursday, and sharp drying commencing, and Td
values lowering.

Increasing atmospheric wind shear will raise the odds a bit of a
severe TSTM wind gust, mainly Tuesday afternoon to Wednesday
morning. The forward speed of the storms from the WSW to ENE
could drop strong wind, MLCAPE/MUCAPE progged around 2000 j/Kg
and partial sunshine will create locally higher SBCAPE and spur
differential heating Tuesday afternoon. The SPC has place
portions of the region in `marginal` risk, favored to NC moreso
than SC. QPF values not that high Tue/Wed as convection is apt
to be in hit and miss coverage, generally 0.25" SC and 0.50" NC,
`basin average` rainfall.


&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 3 PM Sunday...Mid-level pattern will be marked by 5h trough
through Fri before weak 5h ridge expands east over the area. Lack of
deep moisture will limit precip chances somewhat during the period,
the best chances likely being Wed as the arriving trough pushes a
cold front into the area. Surface high building in ensures the
front and deeper moisture shift a little farther offshore into
the weekend. At this point uncertainty creeps in concerning how
quickly a weak coastal trough develops and then moves onshore as
the high to the north shifts east. Will continue to carry
chance pop Wed with chance to likely pop Wed night. Once the
front is through, confidence in the forecast decrease and will
carry slight chance to chance pop for the remainder of the
period. Given the lack widespread deep moisture think diurnal
activity will be limited along the sea breeze and any lingering
boundaries. Temperatures start off above climo but following the
passage of the cold front later Wed temps drop below climo for
Thu through Sun.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
As of 06Z...Once again similar conditions expected regarding
the evolution of showers and thunderstorms for the mostly
daytime period. Expect mainly VFR conditions as the coverage
should once again be limited. As for the next few hours, fairly
strong signals that LBT and FLO will see at least a brief period
of IFR fog and or stratus and used tempo groups to address.


Extended Outlook...Scattered showers and thunderstorms each
afternoon and evening, accompanied by brief MVFR conditions.
Cold front late in the period Thursday may cross all terminals
of SE NC and NE SC, bringing a surface wind- shift.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 338 AM Monday...Expect southwest winds through the period
as the synoptic pattern remains all but unchanged through early
Tuesday. Wind speeds will be 10-15 knots with some intervals of
15-20 knots which will mostly occur during the overnight hours.
Significant seas will remain generally consistent as well with
a range of 2-4 feet. Even with the higher winds both currently
and again Tuesday morning the need for a SCEC headline is not
anticipated.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 338 AM Monday...Not ideal marine conditions, as SW winds
this period begin to pick ahead of an approaching cold front
set to cross the coast around daybreak Thursday. Tuesday
afternoon through early Wednesday, 15-20 kt winds and a few
gusts to 25 kt likely. Thus a brief SCA cannot be ruled out this
period ahead of the cold front. TSTMS will be moving to the
ENE-NE and radar updates are recommended before venturing
offshore this period. The bulk of wave energy is wind driven
this period with dominant wave periods around 5 seconds. Winds
shifting to N-NNE after sunrise Thursday.

LONG TERM /THURSDAY THROUGH FRIDAY/...
As of 3 PM Sunday...Pinched gradient Thu morning leads to
slightly increased northeast flow, an event that will be
repeated late Thu night as secondary northeast surge sets up.
Second round Thu night will be stronger with solid 15 kt winds
possible. Seas 3 to 5 ft at the start of the period gradually
fall to 3 to 4 ft late Wed and Wed night and 2 to 3 ft Thu and
Fri.

&&

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

&&

$$

SYNOPSIS...8
NEAR TERM...SHK
SHORT TERM...MJC
LONG TERM...III
AVIATION...SHK