-- Discussion containing changed information from previous version are highlighted. --
442
FXUS62 KILM 212354
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
754 PM EDT Wed Jun 21 2017

.SYNOPSIS...
Tropical moisture will lessen across the area which will result
in fewer showers and thunderstorms through Friday. The remnants
of Tropical Storm Cindy should reach the southern Appalachians
Friday night with its associated moisture increasing the risk
for showers and thunderstorms Saturday. A cold front will stall
in close proximity Sunday and Monday. Finally, the cold front
will move offshore, bringing cooler and much drier air into the
area Tuesday and Wednesday.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 3 PM Wednesday...Transition to a weak zonal flow aloft with
little to no upper support appears in the cards overnight. There may
be developing convection tonight over the waters as the nocturnal
buoyancy ramps up, or as a weak land breeze forms, but the steering
flow will prevent them from reaching onshore. As a result am
debating scaling back POP values below mentionable values overnight,
at best isolated. Another observations is the precipitable water
decrease overnight.

Thursday appears quiet overall, plentiful high clouds may dampen
surface heating, limiting convective generated rain. Saturation
aloft may lead to a few drops from mid-level clouds, but chance
of measurable rainfall Thursday appears to remain low-end. H6-H4
omega however warrants a slight chance of rain and this may be
stratiform in nature. Very low QPF numbers this time period.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...High pressure aloft, centered offshore of
the east coast of FL at the start of the period will help guide
Tropical Storm Cindy northward and eventually into the stronger
westerlies where it will weaken. Cindy will get intermingled with a
frontal boundary with the remnants of Cindy expected to move into
the southern Appalachians Fri night.

The circulation associated with Cindy is expected to mop up much of
the deep moisture that has been streaming across the Carolinas from
the Gulf of Mexico in the last several days. Precipitable water
values are finally expected to be on a downward path from near 2
inches Thu eve to near 1.5 inches on Fri and Fri night. Some ridging
will also help to suppress convection during this time and will
carry slight chance/small chance for showers and thunderstorms Thu
night and Fri and then keep POPs below threshold Fri night, although
organized convection should be just upstream of I-95 by daybreak Sat.
Nocturnal jetting is evident both nights, strongest Fri night as the
pressure gradient tightens up ahead of the remnants of Cindy and the
approaching trough. Wind speeds about 1500 ft up will be up to 25 to
35 kt Fri night. Model profiles show a distinct subsidence inversion
and would not be surprised to see a good amount of nighttime stratus
develop and this is something the models are hinting at.

Nighttime winds should be elevated, especially Fri night and lows
during this time will be above normal, low and mid 70s Thu night and
mid and upper 70s Fri night. A warm and humid day is expected Fri
with highs in the upper 80s and lower 90s. It will be breezy on Fri,
especially at the coast where the seabreeze circulation will push
wind speeds up to 20 to 25 mph during the afternoon.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...Potentially very unsettled through the
period but lots of uncertainty exists even in the first part of the
extended.

Remnant mid-level vorticity from TS Cindy will be ejecting east
across the Carolinas during Saturday. This feature will be
accompanied by a weak surface low, likely moving near the NC/VA
border, and will bring a surge in PWAT due to the tropical origin of
the remnants. This will likely bring showers and tstms with periods
of heavy rainfall through Saturday before the trailing cold front
moves offshore. The caveat to this is that while the front tries to
push east, the mid-level pattern features an amplification of the
ridge across the east, thus slowing and stalling the front. Where
this front stalls will be key to the Sun/Mon forecast. The GFS
stalls this front along the coast with continued showers and storms
due to deep SW flow and overrunning, and potentially secondary low
development. The ECM/CMC push the front far enough offshore to
create dry weather the latter half of the wknd. Climatologically the
stalled boundary makes sense, and is supported by WPC progs, so will
maintain the inherited unsettled forecast into early next week with
temps cooling to below climo after a very warm Saturday.

Anomalously deep longwave trough then digs into the east clearing
the front and bringing much cooler temperatures to the region. 850mb
temps may drop towards 10C by the middle of next week, which is
below the 10th percentile for late June, suggesting highs and lows
several degrees below climo along with a much drier and refreshing
airmass.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
As of 00Z...Insolation reaching the sfc has been kept at bay
from the blanket of mid and upper level clouds. As a result,
only expect vcnty shra early this evening. Otherwise, the next
shot of MVFR/IFR will occur between 08Z and 14Z from low
ceilings. Model MOS Guidance continues to show sub 1k foot
ceilings during this time-line and see no reason to detour from
it`s prognosis. Winds will drop off to calm conditions at times
which brings up the possibility of fog and how much of it. For
now, will stick with the low stratus or stratus fractus
ceilings. For daytime Thu, the area terminals will be under the
veil of mid and upper level clouds basically the exhaust clouds
from Cindy. Any insolation that makes it to the sfc, will be
enough for a SCT/BKN Cu deck in the 2.5k to 5.0k foot range
during Thu aftn/eve. Will also indicate VCSH after 1900Z for all
terminals. Forcing mechanisms will remain lackluster for
convection initiation but enough to atleast have vcnty shra.

Extended Outlook...MVFR ceilings/vsbys Saturday as tropical
moisture associated with Cindy remnants traverse the region.
Patchy fog and low ceilings possible 08z-13z Friday.
-- End Changed Discussion --

&&

.MARINE...
NEAR TERM /THROUGH THURSDAY/...
As of 3 PM Wednesday...A manageable marine environment tonight
and Thursday, essentially SW winds 10-15 KT and seas around 3
feet. The wave energy will be primarily from the S every 6-7
seconds mixed with very weak ESE swell of a foot or less.
Isolated to scattered showers are possible overnight, with only
a slight chance of a TSTM, mainly favored near or over the Gulf
Stream. A changing steering flow aloft will guide any showers or
storms developing over the waters farther offshore versus
onshore.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...Winds will strengthen as we progress from
Thu night into Fri night as the pressure gradient tightens between
the approaching remnants of Cindy, crossing the southern
Appalachians Fri night, and the Bermuda High centered offshore.
Nocturnal jetting is evident both nights. We will likely reach Small
Craft Advisory thresholds late in the day Fri and Fri night. Wind
speeds will be increasing to 10 to 15 kt Thu night, 15 to 20 kt Fri
and up to 20 to 25 kt Fri night. The direction will be SW. Seas will
build to 3 to 4 ft Thu night, 4 to 5 kt Fri and 4 to 6 ft Fri
night.

LONG TERM /SATURDAY THROUGH MONDAY/...
As of 300 PM Tuesday...High pressure offshore will gradually
retreat as a cold front approaches from the west. Ahead of this
front, a weak wave of low pressure, the remnants of TS Cindy,
will move near the area bringing showers and storms to the
waters Saturday. Additionally, as the gradient pinches ahead of
the front, SW winds will increase to 15-25 kts, building seas to
4-6 ft, and an SCA will likely be needed much of Saturday.
Thereafter, the front will waver in the vicinity Sunday and
Monday before finally pushing offshore late in the period. This
will create a weaker gradient and wind speeds around 10 kts,
with direction varying from S to W at times. After the seas fall
below SCA thresholds Saturday night, they will continue to drop
to just 2-3 ft late Sunday and remain at these amplitudes on
Monday.

&&

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

&&

$$
SYNOPSIS...JDW
NEAR TERM...MJC
SHORT TERM...RJD
LONG TERM...JDW
AVIATION...DCH