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000
FXUS62 KILM 161036
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
636 AM EDT Thu Aug 16 2018

.SYNOPSIS...
Bermuda high pressure will maintain warm and humid weather with
mainly isolated thunderstorms through Friday. Rain chances will
increase a bit into the weekend, as an upper trough deepens to
the west, and a surface front moves into the Carolinas.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Thursday...Expect some patchy fog this morning,
especially any places that had convection previously, leaving
shallow moisture. After sunrise, fog will dissipate leaving
sunshine mixing with mainly some high clouds.

Ridge axis running back across the Southeast from the
Atlantic waters to the east. This will maintain enough dry air
and subsidence aloft to keep convection more isolated,
basically focused along sea breeze boundary and along inland
trough. Models do show a minor perturbation running across
mainly NC this evening which may help to push a bit of
mid to high clouds or convection into the area from trough to
the west, but overall expect isolated convection along sea
breeze earlier. HRRR shows main focus along the coast near the
Grand Strand this aftn and then along NW bordering counties this
eve with pcp water values increasing at that time to 1.8 to 2
inches. Winds become a little stiffer out of the SW heading into
Fri morning, with a chc of convection along the Cape Fear coast
toward morning.

Continued SW flow around Bermuda High pressure will produce
warm and humid weather today. Expect temps to reach between 90
and 95 most places combining with dewpoints in the low to mid
70s to generate heat index values near 100 this aftn. Winds will
naturally back slightly and spike up in the afternoon sea
breeze and slight pinching of the gradient between the high
pressure and inland trough.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 300 AM Thursday...A positively tilted upper trough extending
from the Great Lakes to the Gulf Coast will slowly advance eastward
Friday and Saturday. Deepening moisture ahead of the trough should
build precipitable water values toward 2.00 to 2.25 inches. Bermuda
high pressure centered about 500 miles off the coast on Friday will
begin to move Saturday as the upper trough advances eastward.

With the approach of the trough, any residual subsidence inversion
aloft with the Bermuda ridge will dissipate during the day Friday.
Expect the coverage of thunderstorms to increase versus Wednesday
and Thursday, reaching 30-40 percent on Friday and 60-70 percent on
Saturday. Shear across the 0-6 km layer should remain only 10-15
knots through the period, favoring only weak storm organization.
Lightning, training cells along boundaries, and heavy rainfall may
turn out to be the biggest risks with this pattern. Thunderstorms
should have diurnal peaks in coverage both Friday and Saturday
afternoons, plus models show a secondary peak in coverage late
Friday night as a weak shortwave over the northeastern Gulf is
pulled across the area.

Our airmass will remain seasonably warm and humid. 850 mb temps
around +18C both days would yield low to mid 90s for highs, but the
increase in clouds and precip should hold us to 90-92 inland and
upper 80s near the coast. Overnight lows in the lower to mid 70s,
except a little warmer on the beaches.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...An active period of weather looks
likely much of the extended as a series of fronts/troughs
impacts the Southeast. The first of these will be driven beneath
a mid-level shortwave digging into the area into Sunday.
Although the trough axis is progged to shift offshore late
Sunday, ahead of this occurrence moisture will stream into the
region with PWATs surging towards 2.25 inches. This moisture
will work in tandem with convergence near the surface boundary,
height falls, and moderate diffluence on the RRQ of an upper jet
angling across New England to produce scattered to potentially
widespread showers and tstms, especially on Sunday. The surface
boundary will linger into Monday but other forcing weakens, so
convection chances remain elevated, but lower than during the
weekend. A brief period of shortwave ridging on Tuesday which
will bring somewhat above normal temps and drier weather,
another mid-level trough and cold front will move into the
Southeast by the end of the period. Temps through the period
will be around to slightly above normal for highs, with above
normal mins likely each night. Cloud cover and convection may
keep temps a bit cooler than progs for the weekend before subtly
warmer conditions develop early next week.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
As of 12Z...Patchy early morning fog inland should burn off
quickly this morning with VFR conditions prevailing through the
day. Isolated thunderstorms will develop this afternoon between
17-19Z, but coverage is only anticipated to be 20-30 percent,
too low for explicit mention in the terminal forecasts at this
time. Any storms that do develop should move toward the east
around 10 knots and will be efficient lightning producers with
gusty winds possible.

Extended Outlook...Mainly VFR conditions expected through Friday
except for areas of pre-dawn ground fog. The potential for
thunderstorms with MVFR/IFR conditions increases by late Friday
and becomes even more likely during the weekend.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Thursday...Southwest flow will continue around
Bermuda High basically 10 to 15 kts. Slightly longer period, up
between 8 and 9 second SE swell will mix with shorter period
wind waves to produce seas just around 3 ft with potential for a
few 4 fters in the outer waters tonight. The flow will back
slightly and become slightly higher and gustier in aftn sea
breeze and slightly pinched gradient between high pressure to
the east and trough inland. Also may see some nocturnal jetting
helping to boost winds up a bit overnight. Basically expect
seas around 3 ft with a few 4 fters possible in outer waters.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 300 AM Thursday...Bermuda high pressure centered about 500
miles off the Southeast coast Friday will drift farther out to sea
on Saturday. Low pressure will move east across New England and drag
a cold front into the Mid-Atlantic states by late Saturday. While
the front should remain to our north, its proximity should lead to a
tighter pressure gradient across the Carolinas with stronger wind
speeds expected across the coastal waters. SW winds 10-15 kt Friday
could increase to 15-20 kt on Saturday, accompanied by several waves
of showers and thunderstorms. Seas should build from 2-3 feet on
Friday to 3-4 feet Saturday, unfortunately with most of that
increase in the choppy end of the wave spectrum.

LONG TERM MARINE /SUNDAY THROUGH MONDAY/...
As of 330 PM Wednesday...High pressure offshore will remain in
place which will force an approaching cold front to stall and
dissipate as it approaches the area late in the weekend into
early next week. This will drive SW winds of 15 to 20 kts
Saturday, easing a bit to around 15 kts Sunday, before falling
off moreso on Monday thanks to the weakening gradient. A low
amplitude 1ft/9sec SE swell will persist through the period, but
the primary wave group will remain a 5 sec SW wind wave at 3-4
ft. This will produce significant seas of 3-4 ft Sunday,
falling to 2-3 ft Monday.

&&

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

&&

$$

SYNOPSIS...RGZ
NEAR TERM...RGZ
SHORT TERM...TRA
LONG TERM...JDW
AVIATION...TRA