Scientific Forecaster Discussion
fxus62 kilm 162027
Area forecast discussion
National Weather Service Wilmington NC
327 PM EST Tue Jan 16 2018
weak high pressure will slip offshore tonight. A cold front
will cross the coast late Wednesday, bringing a mix of rain and
snow, with small accumulations possible inland across southeast NC
Wednesday and Wednesday evening. Cold and dry Arctic air will
build in late Wednesday and Thursday. Temperatures will warm
into the weekend, as high pressure moves offshore. Another cold
front will bring rain chances early next week.
Near term /through Wednesday night/...
as of 300 PM Tuesday...main headline for the near term, 'winter
weather advisory' posted for inland portions of the area, for
the potential of around an inch of snow, possibly closer to 2
inches over northern Marlboro County. A rain/snow mix will be
underway at daybreak west of I-95, spreading eastward, with the
leading edge of stratiform precipitation reaching the coast
midday to early in the afternoon. Areas outside of the advisory,
may see snow as well, but less than 1 inch of accumulation
expected. The rain and snow will be off the coast in the
Adjustments to the advisory may be made overnight with new data,
and we cannot rule out completely, a 'winter storm warning' if 2
inches is expected within 12 hours for portions of the I-95
corridor. Evaporative cooling and cold air advection will keep
maximum temperatures locked into the 30s inland, and 40s near
the coast Wednesday. Snow may not change over to rain near
coastal zones, or if so, not until evening, when temperatures
finally become cold enough, chasing the moisture to sea.
Short term /Thursday through Thursday night/...
as of 300 PM Tuesday...a northwest flow aloft will prevail through
the period as surface high pressure builds in from the west.
Essentially a temperature forecast as any moisture will be well
off to the northeast. Lows Thursday morning will be in the lower
20s with daytime highs in the lower to middle 40s. Some air
mass modification will keep temperatures a little warmer Friday
morning with mostly middle 20s.
Long term /Friday through Tuesday/...
as of 300 PM Tuesday...surface high centered over southern Alabama Fri
morning will shift east for the weekend, moving offshore. Very dry
air in place, precipitable water will be under a quarter inch Fri
and Sat, ensure the region remains dry. Near climo temperatures Fri
will start warming Sat as weak low level warm advection begins. The
progressive mid-level pattern, responsible for the surface high's
rapid shift east, will become a little more amplified as a southern
stream shortwave moves along the Gulf Coast this weekend. The wave
weakens/opens up as it lifts into the southeast and it seems
unlikely that it will be accompanied by any rainfall as it passes
late Sat night and sun. Weak 5h ridge starts to build over the
western Atlantic early next week which, coupled with low level warm
advection, leads to a warming trend sun and Mon.
Best precip chances during the period continue to be associated with
cold front crossing the area late Mon or Mon night. Parent low
remains displaced well north of the area, moving across the Great
Lakes and southern Canada. Although there is a brief period of
moisture return ahead of the front, moisture will be limited and
current chc pop Mon and Mon night seems reasonable. Cold advection
is limited behind the front as the 5h trough lifts northeast instead
of moving overhead. Lack of cold advection combined with the return
of the 5h ridge over the western Atlantic will keep temperatures
near to slightly above climo in the Post front environment.
Aviation /20z Tuesday through Sunday/...
as of 18z...moderate confidence that wintry weather is on the way.
Increasing clouds tonight as the cold front approaches. The inland
terminals will see weather several hours before the coastal
terminals. Precip will likely start out as rain, or a rain and snow
mix. Cold air advection will bring temps at 850 mb down to -4 to -5
celsius, and this will cause the precip to change to complete snow
by early afternoon. The changeover will cause ceilings and
visibilities to quickly lower to IFR/LIFR. The coastal terminals
will still be VFR at the end of the forecast period, but will be
going downhill from there.
near term /through Wednesday night/...
as of 300 PM Tuesday...a decent marine period, prior to
worsening late on Wednesday, as a cold front spills colder air
over the waters. North-northwest winds and wind-chop, mainly light, will
mix with east swell this period tonight and Wednesday, with
significant wave heights of 4 feet or less. Late Wednesday, rain
may begin to reduce visibilities.
Short term /Thursday through Thursday night/...
as of 300 PM Tuesday...expect blustery winds behind a departing potent
mid level system on the order of 20-25 knots from the northwest for
a few hours. With the new airmass coming in from the west, cold air
advection isn't as strong as we have seen the past few events and
winds diminish quickly Thursday to 10-15 knots from the
west/northwest where they will remain for the most part through
Friday morning. Significant seas will be 4-7 feet early on falling
in concert with the winds to 2-4 feet by Friday morning.
Long term /Friday through Sunday/...
as of 300 PM Tuesday...weak surface high southwest of the waters Fri
morning will quickly shift east. Southwest flow on the low end of
the 10 to 15 kt range Fri drops to around 10 kt by Sat morning. The
center of the high expands over the western Atlantic with the
surface pressure gradient becoming ill-defined. Winds will drop
under 10 kt late Sat night and remain light and variable sun with
the surface ridge axis in the region.
SC...Winter Weather Advisory from 4 am to 7 PM EST Wednesday for
NC...Winter Weather Advisory from 4 am to 7 PM EST Wednesday for