Scientific Forecaster Discussion
fxus62 kilm 171952
Area forecast discussion
National Weather Service Wilmington NC
252 PM EST sun Dec 17 2017
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 230 PM Sunday...a shortwave, currently dampening across the
Midwest, along with a deepening upper low across northwest Mexico is
directing southern stream moisture toward the Carolinas. Clouds will
continue to be on the increase and low-level Theta-east advection plus
weak upward vertical velocity 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
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 west-southwest
flow Monday evening could bring a few rain drops from flaccid
convection over NE SC, otherwise not a great expected in the
rain department. A much stronger impulse/short-wave will bring
rain chances late Tuesday night from the west-west-southwest , with
significant quantitative precipitation forecast 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 /18z Sunday through Friday/...
as of 16z...weak low pressure will approach the region this evening.
Look for light southerly flow this morning. Mid and high clouds will
arrive this afternoon with rising dewpoints. Cloudy skies are
expected through the overnight hours, worst case MVFR ceilings and
visibilities after midnight. Continued cloudy on Monday with light
and variable winds.
Extended outlook... unsettled weather Monday through Thursday
morning as a near stationary front moves in and out of the region.
near term /through Monday/...
as of 230 PM Sunday...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
west-SW and gradually increase to 10-15 knots during the day as high
pressure becomes established farther S and southeast 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...as of 3 PM Sunday...a navigable, traversable,
and accessible marine period with west-SW winds 15 knots or less this
period. Sea height will average around 2 feet, but up to 3 feet
across the very outer waters. Very weak east-southeast 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.