Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 180252
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
952 PM EST Sun Dec 17 2017

.SYNOPSIS...
Mild air will surge into the region Monday and Tuesday ahead of
low pressure will approach from the west. This system will bring
moderate rain Wednesday and Wednesday night. High pressure will
build in Thursday and then weaken on Friday as a cold front
slowly approaches from the west.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 955 PM Sunday...A 500 mb ridge centered over Cuba extends
northward along the Southeast coast. A shortwave embedded
within the flow over the ridge tried very hard to squeeze some
light showers this evening from a mid-level deck of moisture
with bases 8000-10000 feet. MRMS precip estimates were as high
as 0.04 inches over Lumberton, but the LBT ASOS reported only a
trace. The culprit was very light precipitation rates plus a
4000-5000 foot deep layer of very dry air with dewpoints below
-20 F which showed up on this evening`s 00Z MHX sounding. With
clouds likely remaining with us the remainder of the night I
have tweaked forecast lows up slightly, with mid to upper 40s
forecast to most locations. Discussion from 230 PM follows...

A shortwave, currently dampening across the Midwest, along with
a deepening upper low across NW Mexico is directing southern
stream moisture toward the Carolinas. Clouds will continue to be
on the increase and low-level Theta-E advection plus weak UVV
later this afternoon and evening will result in widely scattered
shower activity. Rainfall chances will decrease later this
evening with the precip quickly exiting off the coast. Time-
height cross sections show considerable moisture in the lower
levels into Monday, however decent drying is expected above H85,
especially across the northern half of the forecast area. Thus
while cloud cover will continue the best chances for rain Monday
will be found across the southern zones. Cloud cover and lack
of cold advection will hold lows in the mid to upper 40s
(warmest coast) tonight. Higher low-level thickness values
during Monday suggest a nice warm- up into the mid 60s most
areas, which is a category or so warmer than normal.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 300 PM Sunday...Primary headline this period, "Plenty Clouds
and Mild, Low Rain Chances". Weak impulses caught in swift WSW
flow Monday evening could bring a few rain drops from flaccid
convection over NE SC, otherwise not a great deal expected in the
rain department. A much stronger impulse/short-wave will bring
rain chances late Tuesday night from the W-WSW , with
significant QPF in the cards after daybreak Wednesday. Surface
high pressure will remain anchored over Florida and the Bahamas
this period. If you enjoy daytime temperatures in the 70s, then
you should go outside Tuesday. The coolest portion of this
time- frame is at daybreak Tuesday, upper 40s to around 50.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 300 PM Sunday...A front will be draped over the area on
Wednesday while a fast moving upper disturbance and flat surface
wave of low pressure approach from the west. There is some
unresolved differences in the track of this low, with some
ramifications of Wednesday`s highs and perhaps the distribution of
the max precipitation. In the wake of this system, which could bring
a healthy dose of rain high pressure wedges in from the north on
Thursday. This wedge will weaken but largely remain in the
Carolinas, allowing for a moderation towards warmer temperatures. It
then lifts out by Saturday clearing the path for warm and moist
advection ahead of the next cold front, previously slated for
arrival Saturday but it now appears to be up to two days slower.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 23Z...Latest surface analysis shows a frontal boundary
across the Gulf Coast states reaching into SC with a weak area
of low pressure across LA that will slowly move along this
boundry overnight into Monday. Model sounding from GFS shows
plenty of low level moisture across the region underneath an
inversion. GFS/NAM differ on ceilings with GFS initializing
better than NAM so will favor the GFS solution. Ceilings around
8-10Kft will slowly lower during the overnight period and
between 10-12z drop the terminals into MVFR below 3Kft. Could
also see some patchy fog across the terminals as well...last
night KCRE dropped to below 1 mile with calm winds not sure if
we will get down that low but it is possible for less than an
hour but confidence is low in vsby forecast for KCRE. Elsewhere
4-6sm in br is forecasted. Winds will remain light and variable
or calm across the terminals overnight becoming SW at 5-10 kts
on Monday. Models hint at some light precipitation towards the
end of the TAF period but I will leave out for now as vsbys will
remain above 6SM and precipitation will be light if any.
Moderate degree of confidence in MVFR for terminals throughout
the day on Monday.

Extended Outlook... Unsettled weather Monday through Thursday
morning as a near stationary front moves in and out of the region.

&&

.MARINE...
NEAR TERM /THROUGH MONDAY/...
As of 955 PM Sunday...No significant changes are needed to the
forecast. Very light winds and flat seas continue. Radar shows
only some light sprinkles/showers north of Cape Fear, but few
locations will see any rain tonight. Discussion from 230 PM
follows...

Atypically benign marine conditions for the middle of
December will persist through tonight thanks to surface high
pressure in place over the area. Seas will be 2 ft or less with
winds 10 knots or less tonight. The weak pressure gradient will
carry into Monday morning as well, however the flow will become
more W-SW and gradually increase to 10-15 knots during the day
as high pressure becomes established farther S and SE of the
waters. Potential for a few showers across the waters tonight as
well.

SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 300 PM Sunday...A navigable, traversable, and accessible
marine period with W-SW winds 15 KT or less this period. Sea
height will average around 2 feet, but up to 3 feet across the
very outer waters. Very weak ESE swell, a foot or less every 8-9
seconds, will co-mingle with SW wind-waves and chop. Isolated
light showers Monday evening, and again very early Wednesday as
several disturbances pass overhead. Showers to be favored over
the SC waters Monday evening, more widespread into early Wed.
Surface high pressure will remain anchored over Florida and the
Bahamas this period.

LONG TERM /WEDNESDAY THROUGH FRIDAY/...
As of 300 PM Sunday...With a front stalled over the area but at
an uncertain latitude there is some uncertainty related to
Wednesday`s wind forecast. There is also some uncertainty
regarding wind speed. For now though the current solution
favored keeps the front to our north and allows an approaching
wave to ramp up wind speeds later in the day Wednesday. Once
this low moves by high pressure will nose in from the north and
turn winds decidedly NE. A short-lived advisory is tough to rule
out either ahead or behind this system, or both given the
aforementioned uncertainties. As the high weakens heading into
Friday looking for decreasing and veering winds.

&&

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

&&

$$
SYNOPSIS...MBB
NEAR TERM...TRA/SRP
SHORT TERM...MJC
LONG TERM...MBB
AVIATION...MAC
MARINE...


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