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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 252251
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
651 PM EDT Tue Sep 25 2018

.SYNOPSIS...
Low pressure offshore will remain east of Cape Fear this evening
before moving across the Outer Banks late tonight. Warm
temperatures will prevail this week ahead of a slowly
approaching cold front. The front will stall across the area
Friday through the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 700 PM Tuesday...Showers moved as far west as Lumberton,
Fair Bluff, and Conway today in the broad outer envelope of a
tropical disturbance centered about 100 miles southeast of Cape
Fear. Reconnaissance aircraft flying through the disturbance
this evening found a 1016 mb low and a closed circulation at the
surface, but the system currently has insufficient convection
to qualify as a tropical depression. The inland line of showers
should die away over the next couple of hours, although I`m
keeping a 20-30 PoP going from here to the coast through about
10 PM in case other showers develop within the conditionally
unstable airmass and convergent low-level wind regime.

Plenty of low-level moisture, gradually drying mid-levels, and
light surface winds will set the stage for fog and/or low
stratus clouds late tonight, particularly north of Florence,
Marion, and Myrtle Beach. Guidance and persistence indicate
conditions should begin to deteriorate around 5 AM. Very few
changes were needed to the forecast this evening aside from
updating the current location of the showers and clouds.

Discussion from 300 PM follows...

A weak frontal boundary was lingering near the Carolina coast
as an area of disturbed weather associated with low pressure
well off shore was moving westward toward the Cape Fear coast.
This has produced a gusty NE flow across the area. Cu field was
blanketing most of the area leaving breaks of sunshine this
afternoon. Expect sunshine to continue to increase in spots,
while showers continue to rotate around outer circulation of low
pressure off shore, with most of them weakening or dissipating
as they reach the coast. Dry air and subsidence further outside
of low circulation will push inland limiting convection there.
Intermittent lines or bands of showers will continue to move
toward the Cape Fear coast northward. As these showers move on
shore they could produce a brief period of gusty winds and heavy
rain. Other showers were developing along convergence
associated with weakening frontal boundary or sea breeze front
in NE flow backing to the NW further inland.

As the low off shore tracks toward the Cape Fear coast, it will
come up against increasing mid to upper level SW flow which
will help increase shear on the west side and help guide it up
toward the north before it reaches the coast this evening into
overnight tonight. Expect main convective activity to diminish
by late evening as winds back further around to the W-SW with
drier air and subsidence increasing over the area. Pcp water
will basically run around 1.5 inches through the column
overnight with only a slight chc of a shwrs over the adjacent
coastal waters. Expect lows Wednesday morning between 70 to 75
most places.

Ridge aloft will provide plenty of dry air and subsidence aloft
on Wed. Any fog that develops early Wed morning will dissipate
leaving just some cu around and with a westerly downslope flow,
and subsidence aloft, expect plenty of sunshine and limited
shwr activity with warm temps into the mid 80s. Mid to upper
trough will push a cold front toward the Carolinas late Wed and
moisture pooling out well ahead of the front in deep SW flow
will produce some late aftn convection, but counting on much of
the activity to remain west of local forecast area. Included
lower end pops, mainly over I-95 corridor and west later Wed
aftn, toward end of this period.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...a mid-level pressure trough will move
over the eastern 2/3rd of the United States. At the surface a
cold front will be in the central Carolinas and the 12 UTC NAM
has it becoming stationary farther inland than the 12 UTC GFS
which brings this boundary closer to the coast.

What this front does is brings a ribbon of 2"+ precipitable water
values over our area. With weak synoptic lift along the weak front,
scattered showers and thunderstorms are possible through the
forecast period and they may become more numerous on Thursday
afternoon especially in the counties along Interstate 95. The latest
QPF forecast calls for values of 0.50 to 1.00 inches between
Wednesday night through Thursday night.

Lows will be in the lower 70s inland to the middle 70s at the coast
Wednesday night and Thursday night. The highs on Thursday will be in
the middle 80s with a few upper 80s over the inland sections of
northeast South Carolina.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...Front nearly stalled across the area Friday
into Saturday; with just the slowest of southward drift. Both days
will offer considerable rain chances though rainfall amounts do not
appear high enough to worsen the ongoing river flooding (though
crest recession may be slowed a bit). Thereafter mid level ridge
builds overhead while surface high expands up and down the east
coast and the area should trend towards drying. The building heights
appear to offset the NE to E surface flow to keep temperatures near
to a few degrees above climatology.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...A tropical disturbance centered about 100 miles
southeast of Cape Fear will move northward overnight, remaining
well east of airports in our forecast area. Shallow moisture,
drying mid-level conditions, and light surface winds will
promote the development of fog and/or low stratus clouds late
tonight. Persistence and latest model guidance indicate
conditions should deteriorate around 09Z, with IFR conditions
potentially lingering through 14-15Z Wednesday morning. Some
afternoon thunderstorms are possible after 18Z Wednesday, but
may be too isolated in coverage for inclusion in the forecast at
this time.

Extended Outlook...A cold front will slowly approach the region,
with increased coverage of convection Thursday through Saturday.
Morning fog possible each day.

&&

.MARINE...
NEAR TERM /THROUGH WEDNESDAY/...
As of 700 PM Tuesday...Reconnaissance aircraft flying through
the tropical disturbance centered about 100 miles southeast of
Cape Fear this evening found a 1016 mb low and a closed
circulation at the surface, but the system currently has
insufficient convection to qualify as a tropical depression. Our
coastal waters are well west of the low and will experience only
mild northerly winds this evening, backing around more westerly
after midnight as the low moves up toward the Outer Banks. Wind
speeds should remain 15 knots or less.

Seas 3-5 feet near and north of Cape Fear this evening are
largely the result of the tropical disturbance. The Frying Pan
Shoals buoy shows virtually all of the wave energy is embodied
in an 8-second easterly swell. Seas should begin to diminish
after midnight. Discussion from 300 PM follows...

A weak front will continue to linger along the coast as low
pressure treks toward the Cape Fear coast this evening. This has
maintained a E to NE winds across the waters this afternoon 10
to 15 kts. As the low reaches the waters, it will turn northward
toward Hatteras. This will shift winds around to the NW-W and
eventually SW as it pulls farther off to the north through Wed.
Winds should slowly diminish down to 10 kts through tonight. A
few 5 fters in the outer waters north of Cape Fear will subside
leaving all waters between 2 and 4 ft by morning.

SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 300 PM Tuesday...with the tropical low moving north of
the waters by Wednesday night and a frontal boundary stalling
inland over the Carolina`s, the winds will be from the south to
southwest through the period. The speeds will be around 10 to 15
knots through the period. Seas will be 2 to 3 feet south of
Little River inlet Wednesday night and 2 to 4 feet to the north.
Seas will be 3 to 4 feet through out of Thursday and Thursday
night.

LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 300 PM Tuesday...Southwesterly prefrontal winds will relax as
the approaching boundary lightens the gradient. FROPA and the thus
veering slated for Friday night. N to NE winds will then last for
the remainder of the period. Seas will be slow to build and wave
faces could steepen. Even so, conditions should remain below
advisory thresholds.

&&

.TIDES/COASTAL FLOODING...
As of 300 PM Tuesday...Long fused coastal flood event on the
Cape Fear river ongoing. High tides should just exceed warning
level (6.7ft MLLW) as the flood wave moves down river combining
with astronomical high tides. Please refer to any Coastal Flood
Advisories or Coastal Flood Warnings for further details.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...Coastal Flood Warning until 2 AM EDT Thursday for NCZ107.
MARINE...None.

&&

$$

SYNOPSIS...MBB
NEAR TERM...TRA/RGZ
SHORT TERM...RH
LONG TERM...MBB
AVIATION...TRA
TIDES/COASTAL FLOODING...RGZ