Scientific Forecaster Discussion
fxus62 kilm 240107
Area forecast discussion
National Weather Service Wilmington NC
807 PM EST Thu Nov 23 2017
high pressure north of the area, and low pressure passing
offshore overnight into Friday, will bring cool conditions
along with occasional light rain and drizzle near the coast.
A dry cold front will cross the coast Saturday night followed
by cool and dry Canadian high pressure through early next week.
A warming trend will follow through mid-week, as high pressure
moves offshore, and low pressure approaches from the west.
Near term /through Friday/...
as of 815 PM Thursday...a 500 mb shortwave trough is located
across the eastern Carolinas roughly along the back edge of the
dense cirrus canopy that covers the coastal southeast. This
feature will slowly move offshore over the next 12 hours. The
strongest winds are on the front (east)side of the upper
trough, meaning the feature should be weakening and lifting out
At the surface the front extends across central Florida then
offshore of the Carolina coastline by a few hundred miles.
Several areas of low pressure will develop and move
northeastward along this front overnight into Friday, but with
the eastward movement of the upper system the moisture we have
aloft should become more meager with time. Skies will clear out
for the I-95 corridor overnight, however cirrus and also mid-
level cloudiness will continue along the coast. Light rain has
been awfully persistent just west of Georgetown, SC all evening,
but this should decay in the next couple of hours, with only the
immediate coast as far north as Southport and Carolina Beach
having any real potential of seeing rain overnight.
No significant change has been made to forecast low
temperatures, still anticipated to reach the mid to upper 30s
inland and lower 40s near the coast.
Short term /Friday night through Saturday night/...
as of 228 PM Thursday...in the mid and upper levels the trough
moves off the coast and several spokes of short-wave energy
approaches from the west-northwest Saturday afternoon into the
overnight. There is very little lift shown as most of the energy
stay in Virginia and northward. Moisture is limited so only
scattered clouds are expected through this period. Both of the
12 UTC global models, GFS and ECMWF, concur on no precipitation
Lows on Friday night are expected to range from the middle 30s
inland to the lower 40s at the beaches. On Saturday night lows
are expected to be a few degrees warmer. The highs on Saturday
are expected to be in the middle 60s.
Long term /Sunday through Thursday/...
as of 228 PM Thursday...intrusion of Canadian high pressure to
dominate the first half of the extended period, with dry north
breezes Sunday as the high barges in from the west, remaining
exceptionally dry through Monday, although winds do ease Monday
as the surface high centers over the area. Monday morning will
be the chilliest portion of this period, with widespread 30s and
sub-freezing air over parts of the interior. Tuesday through
Thursday look for warming to trend, as return wind flow becomes
established, and gradual amplification of a short-wave ridge
over the area mid-week, as an upper low migrates eastward across
the mid-Mississippi Valley. The moisture return will bring
slight rain chances Wednesday/Thursday days 6/7. No Arctic air or severe
weather signatures noted on the horizon at this time.
Aviation /00z Friday through Tuesday/...
as of 00z...expect mostly VFR conditions through the period. A
weak and fast moving system moving offshore may bring a sprinkle
or two to the coast the next few hours but it shouldn't impact
aviation concerns. The moisture along the coast will gradually
move off during the day Friday.
Extended outlook...possible showers along the coast Saturday
night, otherwise VFR.
near term /through Friday/...
as of 815 PM Thursday...a front stalled a few hundred miles off
the Carolina coast will have several weak areas of low pressure
develop and move northward overnight into Friday. Each of these
lows will tighten up the pressure gradient for a time, with
winds surging to 20 knots and perhaps gusts to 25 knots. Seas
currently are measured at 4 feet nearshore and 6 feet at The
Frying Pan Shoals buoy offshore. While we do not anticipate
Small Craft Advisory conditions to develop tonight, conditions
may worsen Friday morning as the next wave of low pressure
ripples by, and for this reason we will maintain the Small Craft
Areas of light rain will continue into early Friday morning
before dissipating late.
Short term /Friday through Saturday night/...
as of 228 PM Thursday...high pressure will give way to a cold
front that will cross the waters near sunrise Saturday morning
and shift east and south of the waters by Saturday night. This
front will not be particularly strong. No precipitation is
The winds on Saturday night will be from the northeast at 15
knots then with frontal passage the winds will back to the
west at 10 to 15 knots. As the high builds in the wind will veer
back to the north at 15 to 20 knots late Saturday night. Seas
will range from 2 to 3 feet near shore Friday night to 4 to 5
feet at 20 miles off the coast. On Saturday the seas will drop
only slightly to the 2 to 4 foot range. An increase to 3 to 5
feet between 10 to 20 miles off the coast is possible as a cold
surge works it way south very late Saturday night.
Long term /Sunday through Tuesday/...
as of 228 PM Thursday...the extended marine forecast is one of
improving conditions, as Sunday begins blustery in north wind as
Canadian high pressure builds toward the coast. Following this
however, a vast improvement, as winds ease and Monday into
Tuesday, with light windspeeds. As a result, a notable easing
trend in sea heights as well, with 3-4 foot seas Sunday, slowly
subsiding to 1-2 feet into Tuesday. An 'exercise caution' flag
cannot be ruled out entirely Sunday, but afterward, manageable
marine conditions appear on tap. No thunderstorms expected on the 0-20
nm waters this period.
Marine...Small Craft Advisory until 5 PM EST Friday for amz250-252-254-