Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 060528

Area Forecast Discussion
National Weather Service Wilmington NC
1228 AM EST Tue Dec 6 2016

A strong storm system will impact the region through Tuesday.
Quiet and seasonable weather will occur mid-week ahead of an
arctic front, which is expected to cross offshore late Thursday.
Very cold temperatures will follow for Friday and into the
early weekend.


A powerful southern stream shortwave will eject out of South
Texas this evening and become negatively tilted across the
southern Mississippi Valley overnight. Surface cyclogenesis that
is ongoing across across the northwest Gulf of Mexico will
gradually translate to a classic Miller Type-B scenario early
Tuesday with primary low pressure moving into Tennessee and
secondary low pressure developing off the South Carolina coast
along a sharpening coastal front. Impressive QG-forcing coupled
with pwats surging to near 2.0 inches (well above normal for
early December) will support a large swatch of moderate to
locally heavy rains encompassing all of Southeast North
Carolina and Northeast South Carolina for much of the nighttime
period. Already seeing scattered showers developing across the
southern Savannah River valley along the nose of a strengthening
850 hPa low- level jet. This activity will move into the
southern and southwestern zones by early evening with steadier
rains blossoming over the area shortly thereafter.

Forecasting temperatures tonight is proving tricky with the high
pressure wedge likely to hold firm for much of the night, except
across the far south and along the coast where temperatures
could rise begin to rise closer to sunrise as the coastal front
begins to lift north/inland. With dewpoints holding in the
upper 40s this afternoon, there will likely be some diabatic
cooling at the onset of light rain, which will help drive
temperatures down this evening before leveling off. Favored
lows from the upper 40s northern areas (best potential for a
longer duration of diabatic cooling) to the mid 50s elsewhere.

The rain could become locally heavy at times, especially along
the coast and across the central/southern zones where pwats will
peak near 2.0 inches. There are no real concerns for flash
flooding, but minor flooding of low-lying and poor drainage
areas could occur in areas that typically flood such as
Georgetown. The combination on intense forcing and some mid-
level instability advecting into southern South Carolina could
support a few elevated tstms overnight, roughly along/south of a
Wilmington-Florence line. No severe weather is anticipated


A deep layer ridge hangs on over the region through Wednesday night,
then shifts south and east as the next upper trough moves into the
Ohio River Valley. This upper trough will move into the eastern U.S.
Thursday, then the axis will shift offshore later Friday.

At the surface, high pressure will start off centered northeast of
the area on Wednesday, then shift south over the area on Thursday
and then south Thursday night. By Friday, a strong cold front is
expected to push through the region. Models have not been very
aggressive with producing any significant precipitation with this
front.  In fact, the latest ECMWF barely has any precipitation at
all. Have continued slight chance to very low end chance pops,
mainly over SC where best moisture, upper forcing and low level
convergence will combine.  Any precip should be short lived and
confined to near the surface front. Clearing, cooler and breezy
later Friday morning and afternoon behind the front.

There is some potential for at least patchy fog Wednesday night
given the surface ridge will be centered east-west over the area.
Thus, have put patchy fog in the grids for Wednesday night.

Temperatures will remain above normal through Thursday night, with
highs in the lower 80s, and lows in the upper 50s to lower 60s. By
Friday, much cooler, with highs likely struggling to reach 70 most
areas. These cooler temperatures, combined with breezy northerly
winds, will make it feel a little brisk.


Arctic front to cross the Carolinas Thursday, with very cold
conditions following in its wake. Guidance has slightly
increased its moisture associated with the FROPA, and will carry
SCHC POP for northern zones late Thursday as a few showers are
possible. Increased column saturation above 600mb suggests
increased cloud cover, but very dry air beneath this will
prevent much more than a brief shower or sprinkle with the
FROPA. All precip will be of the liquid variety however, it will
be too warm for any snowflakes this time around. However, it
will certainly FEEL like winter beginning Thursday night and
persisting through Saturday as temps plummet. 850mb temps have
warmed slightly in new guidance as the core of the cold air
deflects to our north, but still expect highs only in the 40s
Fri/Sat with lows dropping well into the 20s Friday night.
Additionally, gusty winds Friday will make apparent temps even
colder than that. The Canadian high pressure bringing this cold
air will shift offshore quickly late in the wknd allowing temps
to recover to seasonable values Sunday.


As of 06Z...High confidence in IFR overnight, and persisting through
much of this valid period. Low pressure consolidating near Florida
will ride up a stalled front just offshore through this period,
creating widespread rain, heavy at times. IFR cigs are slowly
advancing NE tonight, and will envelop all terminals in the next few
hours. Once this occurs, cigs will slowly lower, and LIFR is
forecast much of Tuesday. VSBYS will fluctuate considerably during
periods of heavier rainfall, but MVFR is forecast to be predominant.
Winds will increase from the NE overnight to 10-15 kts, but will
then back to the NW as the low pulls away during Tuesday, driving
the front offshore. This wind shift will create subtle dry
advection, and cigs will gradually improve late Tuesday, with VFR
possibly developing inland by the end of this valid period.

Extended Outlook...Fog possible Tuesday and Wednesday nights.
VFR conditions expected to prevail late week through this


Tonight: North winds will veer to the northeast tonight as low
pressure develops along a sharpening coastal front. A tightening
pressure gradient between the low and high pressure to the
north will support increasing winds, especially from Murrells
Inlet north to Surf City. There are signals that winds could
reach as high as 20-25 kt at times per the latest GFS and to
some extent the NAM, but the various high resolution models are
showing just a tad weaker low-level wind field. Will cap winds
at 20 kt for now and per coordination with WFO Morehead City, a
Small Craft Advisory will not be issued. Concerns will be
passed on to WFO Wilmington after service backup concludes. Seas
will build overnight, reaching 3-5 ft, except 2-3 ft over
northern portions of Long Bay downwind of Cape Fear. Rain could
locally reduce vsbys to less than 1 nm at times.

Tuesday through Thursday Night: No highlights expected through
Thursday night. High pressure will shift from northeast of the
area Wednesday to south of the area by later Thursday. Winds
east-northeast Wednesday, becoming variable Thursday, then
southwest Thursday night. Winds generally 15 knots or less and
seas 4 feet or less.

Friday and Saturday: By Friday, a strong cold front is expected
to push through the waters, with increasing northerly winds and
seas. Expect Small Craft Advisory conditions to develop behind
the front on Friday, with some wind gusts to near gale force not
out of the question. Seas building rapidly to 6 to 8 feet
beyond 20 nm. Small craft conditions likely to persist through
early Saturday. Improving conditions later Saturday through
early next week. No highlights expected for this period as high
pressure builds from the northwest.




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