Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 172251
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
651 PM EDT Wed Oct 17 2018

.SYNOPSIS...
Cool and dry High pressure will build in behind a cold front
tonight. A stronger cold front will move through the area
Saturday night. High pressure will build down from the north on
Sunday, slowly migrating eastward, maintaining cooler weather
through early Tuesday. Low pressure moving across the Southeast
should bring clouds and rain in the second half of next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 700 PM Wednesday...The cold front is coming through in
several pieces. The first piece of the front has pushed all the
way down to Charleston, SC and is discernible as a shift to
northerly winds. The second piece of the front just moved
through Wilmington and Lumberton in the past hour and shows up
as a drop in dewpoints. A third boundary will push through later
tonight, and this is where the real low-level cold and dry advection
will start. Dewpoints will fall into the 50s, then 40s late, as
air temperatures slide into the 50s by daybreak.

Changes with this forecast update include higher sky cover
values this evening due to advection of a thin layer of moisture
over the top of the frontal inversion, and a slight upward
adjustments to forecast lows across South Carolina based on
non-NAM model guidance. Discussion from 300 PM follows...

The cold front has shifted off the coast except for Georgetown
county. The chance of any precipitation is dwindling as the
drier air moves southward and will overtake the entire forecast
area overnight. Cold air advection continue behind the cold
front and low temperatures are expected to fall to around 50
north of a Lumberton to Burgaw line and lower to middle 50s
elsewhere inland. Upper 50s at the beaches can be expected from
Wrightsville Beach southward.

On Thursday, cooler than average highs for the area with maximum
temperatures reaching the middle to upper 60s.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...Though surface winds grow quite light
Thursday night the boundary layer cold advection remains healthy
above the surface. Thus the stage is set for a true taste of Fall as
lows dip into the 40s for the first time since Spring. Friday brings
very light winds as the high moves overhead and then offshore by
evening. Boundary layer isotherms line back up with wind barbs
shutting off the cold air advection. Though shallow mixing may
prevent the temperature recovery from Thursday being quite as much
as previously thought; it looks like most places will touch 70 for a
high instead of low 70s. Both the warm advection and the resulting
increase in cloud cover will keep Friday night quite mild with lows
very near 60; about 10 degrees above climatology.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...Clouds should thicken early Saturday
with increasing chc of pcp as mid to upper trough digs south
from the Great Lakes and pushes a cold front through the
Carolinas. Expect localized potential for higher end QPF in heavier
showers, but overall expect clouds and showers with a slight
chc of a thunderstorm, mainly toward the coast where better
instability is expected. Temps will be modified by clouds and
pcp but WAA ahead of the front will keep temps in the mid to
upper 70s most places.

Dry and cool High pressure will build down from the north on
Sunday, slowly migrating eastward, maintaining cooler weather
for much of next week. Expect some of the coolest temps of the
season Sun through Mon with max temps in the 60s. As high
reaches nearly overhead Sun night, should see more ideal
radiational cooling with a clear sky and near calm winds. The
dewpoints will drop into the mid 30s Sun night allowing temps to
drop down near 40 many places inland just before daybreak early
Mon morning.

By Tues into mid week, the air mass will modify slightly as
high shifts off the coast with models indicating possible
clouds and pcp affecting the area, with better chances along
the coast, as low pressure moves across the Southeast.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 00Z...High pressure will continue to build in through the
overnight hours. Mid and high clouds associated with the jet will
diminish and drop southward toward morning. Cold air advection after
03Z will drop dewpoints and will keep the wind around 10kts and
above by 07-08Z. Nearly clear skies in store for Thursday with a
north northeast wind.

Extended Outlook...Predominately VFR through Friday. Moderate
confidence for showers and MVFR/IFR conditions Saturday associated
with a cold front. Improving conditions Sunday.

&&

.MARINE...
NEAR TERM /THROUGH THURSDAY/...
As of 700 PM Wednesday...Our cold front is coming through in
pieces. The first wind shift has pressed as far south as
Charleston, SC. Northerly winds are now in place over the
entire northern half of South Carolina. Another boundary is
approaching Cape Fear from the north, and yet a third boundary
will push through late this evening. It`s this third piece of
the front that will usher in the increase to 20-25 kt wind
speeds. Model profiles show the potential for 30 knot gusts
developing late tonight due to increasingly chilly air moving
across unseasonably warm water.

Buoy-reported seas are currently 1-2 feet across the coastal
waters, and 3 feet out at the Frying Pan Shoals buoy. Little
change is expected until late this evening when winds increase.

Discussion from 300 PM follows...

The cold front has moved off the coast except for Georgetown,
and the front has not made it to Frying Pan Shoals yet either.
The front is expected to have shifted east of the coastal waters
by 00 UTC. Winds will begin to increase after sunset and
overnight to 20 to 25 knots as the cold air advection behind the
front moves across the waters. Seas will respond and increase
from 2 feet to 4 to 6 feet across the waters with a few 7 foot
waves possible at 20 miles off the coast. Thus the small craft
advisory will remain in effect.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...Post-frontal winds and seas both quickly
abating Thursday night as high pressure builds in and gradient
eases. The high will move overhead on Friday turning winds
clockwise from NE to E and then SE. This veering continues Friday
night as the high moves offshore and a light southerly flow
ensues.

LONG TERM /SATURDAY THROUGH MONDAY/...
As of 300 PM Wednesday...High pressure will shift further off
the coast Sat as a cold front approaches from the NW. expect
increasing S-SW winds on Sat as gradient tightens ahead of the
front. By Sat aftn, this decent southerly push ahead of cold
front will drive seas up to 3 to 4 ft, with some 5 fters
remaining parallel to the coast and mainly in the outer waters
Sat aftn. The seas may level off slightly Sat eve before
increasing again heading into Sat night as Canadian high
pressure builds down behind the cold front into early next week,
with a decent northerly surge up to 15 to 20 kts. This should
keep seas in the 3 to 5 ft range for most waters, reaching near
SCA thresholds. The cold air rushing over the warmer waters
will keep the marine layer well mixed with gusty northerly winds
Sun into Mon. Then winds will diminish and continue to veer
around to a more easterly direction heading through Mon.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory from midnight tonight to 8 PM EDT
     Thursday for AMZ250-252-254-256.

&&

$$

SYNOPSIS...RGZ
NEAR TERM...TRA/RH
SHORT TERM...MBB
LONG TERM...RGZ
AVIATION...DL


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