Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
629 am EST Thursday Dec 5 2013
dense fog will continue as an unseasonably warm and humid air mass
continues to overspread the area through today. Above normal
temperatures will continue through early Saturday. A cold front
will move in from the north on Saturday bringing cooler air and
occasional rain through the latter half of the weekend. A stronger
cold front will move through on Tuesday scouring out any clouds
and unsettled weather and ushering in much cooler and drier air
through middle week next week.
Near term /through tonight/...
as of 630 am Thursday...dense fog advection remains in effect through 900
am EDT this morning for the entire ilm County Warning Area including the adjacent
coastal waters out to 20 nm. Middle to high level clouds approaching
from the SW will help erode the dense part of the fog possibly
earlier than the 9 am time frame. Will monitor.
Upper ridging extending from the Gulf of Mexico...to continue across
the region during this near term period. The upper ridge axis will
slide off the East Coast today through tonight. SW flow aloft will
result with some moisture tapping of the Gulf of Mexico. With a busy
subtropical jet...trajectories indicate Pacific moisture actually
gets tapped. At the surface...high pressure to slide off the East Coast
with its ridge axis extending back across the southeast U.S. The
cold/Arctic front dropping southeast will slow its forward progression
as it becomes oriented parallel to the flow aloft. By Friday morning...
the front will be crossing the Appalachian Mountains across the
Weak middle-level impulse moving NE across the western Carolinas this
afternoon could produce a chance for rain showers...mainly across the
western portions of the ilm County Warning Area. Otherwise...skies across the forecast area
will consist of upper level moisture...and likely diurnally induced
cumulus as maximum temperatures push well into the 70s away from the immediate
coast. Record highs today are around 80 degrees...definitely in
striking distance. For tonight...look for another round of fog
although with additional cloudiness aloft compared to this
morning...it may not be as thick or extensive like this Thursday am.
Along the immediate coast...sea fog will occasionally push onshore
throughout the near term period.
Short term /Friday through Saturday night/...
as of 300 am Thursday...Friday will be the warmest day of the week
and the final day of well above normal temperatures as warm and moist
southerly return flow on Friday gets replaced by cool northerly winds
behind front that will move south of the area on Saturday. The
ridge becomes more well defined off the southeast coast on Friday
holding off cold front which makes very little progress into the
Carolinas on Friday. The gradient between the high pressure off
shore and the cold front approaching will tighten producing an
increase in southerly winds on Friday. Most of the moisture
through the column will be confined to the upper levels above 300 mb.
Therefore expect sun to be filtered out by a decent amount of
cirrus clouds through Friday. Temperatures should soar well into the 70s on
Friday with a very unseasonably warm and humid air mass in place
as 500 mb heights rise to 586 dem and 850 temperatures reach 15 c. Clouds and
continued warm air advection through Friday night will keep temperatures above what normal
day time high temperatures would be for this time of year...closer to 60.
Should continue to see some sea fog across the coastal waters
through the first half of the period as very warm and humid air
advects over the cool shelf waters.
Moisture through the column will deepen Friday night into Saturday as
cold front begins to make progress southeast through the
Carolinas and toward the local area. Expect clouds to thicken with
increasing chance of pcp heading into Saturday as cold front
approaches. Pcp water values around 1.5 inches on Friday will Jump
Up to 1.8 inches along and ahead of cold front as it tracks
through the area on Saturday. Expect most lift and support for pcp
to be located in the vicinity of the cold front as it tracks south
through the area through Saturday morning. The front should clear
the area by early afternoon but this will not lead to clearing as
the shallow cooler and drier air advecting in from the north will
get overrun by stiff southwesterly flow aloft as ridge remains
anchored off shore to the east. This will produce an extended
period of isentropic lift through late Sat into the early sun with
a decent amount of rainfall expected...up around a half inch in
places inland. Overall expect clouds through the period with
rainfall through Saturday as temperatures fall through late day in
shallow cold air advection. Expect a 30 to 40 degree temperature fall from Friday
afternoon to Sun morning.
Long term /Sunday through Wednesday/...
as of 300 am Thursday...a cold front should be draped across
Georgia early Sunday before returning back north as a warm front
late Sunday into Monday. Models continue to show a classic wedge
pattern set up through Sunday with ridge of cool high pressure
inland and coastal trough/front setting up. This cold front will
bring very shallow cold air as the winds aloft remain stiff out of
the southwest. The low level thicknesses drop about 30 M while the
850 temperatures do not show much of drop as the cool air remains very
shallow. The more appreciable pcp should come to an end early
Sunday but expect low clouds and lighter pcp to continue through
much of Sunday as isentropic upglide continues. This will lead to
a decrease in probability of precipitation as the chance of measurable pcp will diminish
through Sunday but intermittent rain/drizzle should continue until
wedge breaks and coastal trough/front pushes inland and north
through the area.
Tough to say when The Wedge will break but it looks like it should
by Monday as next system heads toward the Carolinas from the
northwest. This will lead to an increase in warm and moist air
once again as surface winds increase out the southwest ahead of
approaching cold front. Moisture will deepen through the column
with pcp water values reaching around 1.7 inches by early Tuesday
as cold front progresses through the Carolinas. A very broad middle
to upper trough should push the front through slowly on Tuesday. The
best dynamics with this system look like they will remain to the
northwest of forecast area on Tuesday...but expect showers along and
ahead of front.
Expect clearing Tuesday night into Wednesday with cooler and drier air
moving in for middle week as high pressure builds into the area.
Temperatures reaching up into the 70s on Monday in warm air advection will drop back
down below normal by Wednesday in cold air advection behind front.
Aviation /12z Thursday through Monday/...
as of 12z...patchy dense fog/stratus is being eroded in spots due to
insolation from clouds advecting in. Most of the region will slowly
rise to VFR by 15z or so. A strip of middle level moisture will ride
northeastward and may provide the inland terminals will a sprinkle
or two...minimal aviation impact. This evening...south southwest
flow will raise dewpoints into the low sixties...with sea fog a
definite possibility. LIFR conditions are expected to return to the
region before midnight...continuing through the end of the forecast
Extended outlook...IFR fog/stratus Friday morning. Rain and MVFR/IFR
conditions possible Saturday and Sunday with a cold front. Chance of
rain on Monday.
near term /through tonight/...
as of 625 am Thursday...low stratus and/or sea fog will be the
primary weather stories for the local waters through tonight.
Even with S-SW winds at 5 to 15 knots...the sea fog...a true
advection type fog...will continue to plague the ilm waters. With
Atlantic SSTs in the 50s and 60+ degree dewpoints advecting across
these cooler waters...the result will be an extended round of sea
fog continuing likely for the next 24+ hours in varying degrees of
With the surface ridge axis just south of the ilm waters...look for
winds to come from the S-south-southwest direction. The surface pg will begin to
tighten as a result of the approaching cold front and/or the
retreating Atlantic surface high. Speeds will run 5 to 10 knots
today...increasing 10 to 15 by early this evening...and possibly
up to 20 knots across the warmer SSTs along or just outside of 20 nm.
Significant seas will run 2 to 3 feet...and build up to 4 feet
tonight. Wind driven waves exhibiting 3 to 6 second periods...will
become the dominant contributor to the significant seas.
Short term /Friday through Saturday night/...
as of 300 am Thursday...unseasonable warm and moist air mass will
linger across the waters through Friday into Saturday until a cold
front tracks south through the waters Sat afternoon. This will produce
potential for sea fog through much of the period...but winds will
increase out of the SW up to 15 to 20 kts through late Friday into
Saturday ahead of approaching cold front. This increasing
southerly push will drive seas up to 3 to 5 feet through Friday into
Winds will shift around from SW to north-NE on Saturday behind cold
front as it progresses further south through Sat night. The off
shore flow initially will help to lower seas but by Sat night the
flow should increase out of the NE in more of a pinched gradient as
coastal trough develops with seas reaching back up to 5 feet in
Long term /Sunday through Monday/...
as of 300 am Thursday...northeasterly flow will continue through
early Sunday in pinched gradient between wedge of high pressure
inland and coastal trough/warm front over or just southeast of
local waters. Winds should diminish but remain NE most of Sunday
but at some point will transition to the south again as coastal
trough/warm front pushes north through the waters. For now will
transition to southerly right around midnight Sunday night. Seas
will drop to 2 to 4 feet through Sunday.
Expect increasing S-SW flow through Monday into Monday night as next
cold front makes its way into the Carolinas. SW winds up to 20 kts
will push seas up to 4 to 6 feet Monday.
SC...dense fog advisory until 9 am EST this morning for scz017-023-
NC...dense fog advisory until 9 am EST this morning for ncz087-096-
Marine...dense fog advisory until 9 am EST this morning for amz250-252-