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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KILM 182235
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
635 PM EDT Wed Oct 18 2017

.SYNOPSIS...
Canadian high pressure building into the Mid-Atlantic states
will bring several days of cool, dry weather to the Carolinas.
Temperatures should begin to warm up this weekend as the high
moves off the coast. A cold front will move through on Tuesday
with much cooler temperatures to follow.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 300 PM Wednesday...Surface high to the north will become
elongated later today into tonight. Southern end of the high will
consolidate over eastern TN Thu morning, lingering in the area
through the end of the period. Weak shortwave ridge builds over the
Southeast tonight in the wake of exiting mid-level trough. Ridging
is short lived however as next 5h trough/shortwave moves in from the
northwest on Thu. Forecast soundings show a slight increase in
moisture around 300 mb ahead of the trough. Although moisture is
meager the shortwave could tap into this moisture, producing some
high cloud late tonight into Thu morning. Forecast soundings do not
show quite as much low level moisture along the coast as this
morning, however PVA ahead of the shortwave might be able to
generate a small amount of low cloud along the coast. If forecast
soundings are to be believed the cloud layer would be little more
than a few hundred ft thick. Gradient will start to relax tonight as
the high first elongates then breaks off and starts to consolidate
farther west. Boundary layer winds will still be sufficient for
mixing and significant fog is unlikely. Combination of boundary
layer winds, weak warm advection, and possibility of patches of
cloud will result in lows 5 to 10 degrees warmer than last night.

Thu will be sunny with strong mid-level subsidence keeping a lid on
any upward motion. Precipitable water at or below 0.60 inches will
keep skies clear in the afternoon. Weak but steady warm advection
continues Thu with temps rising into the mid to upper 70s, several
degrees above climo.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...High pressure centered over the
Southern Appalachians Thurs night into Fri will shift slowly
east through the period. At the same time the mid to upper ridge
shifts east building up from the lower Mississippi Valley up
through the southeast following a shortwave which exits off the
southeast coast Thurs evening. This will produce strong
subsidence with plenty of dry in place through the column.
Initially, soundings and moisture profiles show a bit of
lingering moisture stuck under subsidence inversion, but a deep
northerly flow will reinforce dry air in place with pcp water
values dropping from already low values of .6 inches Thurs eve
down to less than .4 inches through Fri aftn. Overall, an
very dry air mass with no chance of pcp and clear blue skies
through Fri. The northerly winds lighten through Fri as gradient
relaxes and winds begin to veer to the NE by daybreak Saturday
allowing for a slight increase in low level moisture by the very
end of the period.

Very dry air in place will allow for large diurnal swings in
temps. Expect overnight lows to be several degrees cooler Thurs
night under ideal radiational cooling conditions and drying
column bringing temps between 45 and 50 most places. After a
very cool morning, temps will recover to near 80 as ridge builds
with h5 height rises and 850 temps increasing up near 14 to
15c. Fri night will see a slight dewpoint recovery but another
decent radiational cooling night with overnight low temps
between 50 and 55 most places.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Tuesday...A highly amplified H5 pattern will prevail
at the onset of the long term period with ridging across the Eastern
United States. At the surface, high pressure will also continue to
ridge across the forecast area as it departs the Mid-Atlantic
Region. As a result, dry weather will continue as temperatures warm
a few categories above normal through the weekend into early next
week. Eventually the H5 and surface ridges lose control as an upper
trough and surface low push eastward. Give this system`s current
progression it appears that there will be a good chance of storms
during Tuesday with a lowering in temperatures Tuesday night into
Wednesday as surface high pressure builds back into the region.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
As of 00Z...Fairly high confidence for VFR through the forecast
period. There may be some sunrise very light fog at CRE, otherwise
P6SM all other terminals. Some stratocu is possible near the coast,
but it should remain scattered. Thursday, continued northeast flow
with high pressure dominating.

Extended Outlook...Tempo MVFR/showers Mon/Tues. Otherwise VFR.

&&

.MARINE...
-- Changed Discussion --
NEAR TERM /THROUGH THURSDAY/...
As of 600 PM Wednesday...Given ongoing Small Craft Advisory
conditions, extended the advisory til 6 am Thu. Across AMZ254, a
Small Craft Should Exercise Caution headline was extended til 6
am thu.

Elongated surface high north-northeast of the waters this
afternoon into tonight will fragment with a new center
consolidating over eastern TN. This will maintain northeast flow
through the period, although the gradient will weaken later
today through Thu. Speeds around 20 kt this afternoon will drop
to 15 to 20 kt overnight and 10 to 15 kt on Thu. Seas across
the outer waters will persist near 6 ft. Seas will be trending
down to 2 to 4 ft Thu.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...High pressure over the southern
Appalachians will shift slowly east through the period with a
weakening gradient flow. This will help veer the winds from N
to NE by daybreak Saturday. Seas will subside from close to 4 to
5 ft off shore Thurs eve down to 2 to 4 ft through the remainder
of the period.

LONG TERM /SATURDAY THROUGH MONDAY/...
As of 300 PM Wednesday...High pressure is expected to shift
farther off the Mid-Atlantic coast Saturday and Sunday allowing
the flow to veer onshore. Southeast flow will further turn
becoming southerly during Monday as an area of low pressure
treks from the Gulf Coast to the western Carolinas. Small Craft
Advisory conditions may be reached late Monday in the
strengthening southerly flow. Seas will be 3-4 ft through much
of the period given the duration and size of the onshore fetch
around the periphery of the aforementioned high pressure.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
As of 10 AM Wednesday...Astronomical tides will peak with the
new moon on Thursday. High tides and strong northeast winds may
combine to push tides above minor coastal flooding thresholds
at Wrightsville Beach and the lower Cape Fear River to include
downtown Wilmington. Advisories may be needed around the time
of high tide through Friday.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
SC...High Rip Current Risk from Thursday morning through Thursday
     evening for SCZ054-056.
NC...High Rip Current Risk from Thursday morning through Thursday
     evening for NCZ106-108-110.
MARINE...Small Craft Advisory until 6 AM EDT Thursday for AMZ250-252-
     256.
-- End Changed Discussion --

&&

$$

NEAR TERM...RJD/III
SHORT TERM...RGZ
LONG TERM...SRP
AVIATION...DL
TIDES/COASTAL FLOODING...III