Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 240535

Area Forecast Discussion
National Weather Service Wilmington NC
135 AM EDT Mon Oct 24 2016

High pressure over the Southeast tonight will be pushed south by a
dry cold front Monday afternoon. High pressure building in from
Canada will bring cool conditions to the region for the middle of
the week. Temperatures will warm late in the week as the center of
the high moves offshore. Thursday night and Friday a weak cold
front slowly approaching from the west may bring a slight chance
of showers.


As of 1230 AM Monday...No changes to the forecast with the latest
update. Previous discussion follows:

A few tweaks to temperatures based on 10 PM observations. No
significant changes were made, except for some 2-3 degree upward
tweaks to low temperatures along the immediate coast from central
Horry County northward to Oak Island. Discussion from 730 PM

Surface high pressure centered along an axis from southern
Georgia to coastal Mississippi will actually retrograde a bit
overnight as low pressure dips southeastward through the Great
Lakes region. The surface pressure gradient will tighten up across
the Mid- Atlantic states while remaining slack over the Deep South
within the ridge.

With good radiational cooling and the boundary layer now
decoupling, greater changes are occurring just above the surface
where the tightening pressure gradient across the Mid-Atlantic
will lead to increasing wind speeds across North Carolina and
points farther northward. Wind speeds at the 975 and 950 mb
levels (roughly 1000-2000 ft AGL) should increase to 25 kt across
Lumberton, while remaining only 10 kt over Georgetown. This
should lead to a large difference in boundary layer turbulence
and the eventual depth of the nighttime radiational inversion.
I`ve therefore lowered forecast low temperatures by almost 10
degrees near the Santee River from Georgetown to south of
Kingstree, with lesser changes farther north.

Along the south-facing coast of Brunswick County, forecast lows
have actually been increased by a few degrees as the west-
southwest wind should advect in heat from the still-warm ocean
where sea surface temperatures remain in the 70s.


As of 300 PM Sunday...Monday afternoon temps shoot up to within a
few degrees of 80 in warm advection ahead of the next cool front.
This boundary moves through in the late afternoon and evening but
it will be running into this bone-dry airmass so no precip. This
next high does not build in as aggressively as the chilly weekend
airmass did. Tuesday and Tuesday night will thus not be as cold or
breezy like Saturday was. Highs should hit the low 70s and lows in
the mid to upper 40s.


As of 300 PM Sunday...Surface high building in from the north Wed
shifts off the coast Thu as cold front approaches from the west.
Front is pushed east by shortwave crossing the Great Lakes Thu into
Fri. Aloft weak shortwave ridge overhead Wed flattens Thu as weak
troughing associated with the aforementioned Great Lakes shortwave
moves east. Moisture return ahead of the front is limited, as are
the dynamics and both the GFS and ECMWF solutions offer limited
precip chances. Best rainfall chances will be Thu night and Fri but
hard to imagine anything more than slight chc pop at this point.
Front is slow to exit the area, in part due to the weakness of the
5h trough, and the surface high building in behind the front lacks
cold air. Temperatures climb from a little below climo Wed to above
climo Thu due to development of return flow. Temps stay above climo
through the period, peaking ahead of the cold front on Fri.
Downslope flow helps keep temps above climo Sat/Sun and, combined
with abundant sunshine, pushes highs into the low to mid 70s.


As of 00Z...VFR. Dry cold frontal passage this afternoon will turn
winds 7 knot SW winds to W AFT 16z at 11 knots or less through the
afternoon hours. Cool air advection tonight will be ushered by NW
winds 7 knots or less becoming N by 6z.

Extended Outlook...VFR. Isolated showers Thursday night.


As of 1230 AM Monday...No changes to the forecast with the latest
update. Previous discussion follows:

High pressure over the Deep South will actually retreat westward
a little overnight as low pressure dives southeastward across the
Great Lakes. The approach of this low should be enough to tighten
the pressure gradient overnight, particularly north of Cape Fear
where wind speeds (currently under 10 knots) should end up close
to 20 knots late tonight! Seas currently 1 to 2 feet should build
by about a foot late tonight, particularly over the North Carolina

As of 300 PM Sunday...Prefrontal WSW winds to shift to NW late
Monday afternoon and evening. There is no strong push of cool
air/high pressure behind this boundary, in contrast to the weekend
FROPA. Conditions will not need any advisory or headlines. Further
veering to NE is then slated for Tuesday as the high progresses
eastward, while remaining well to our north.

As of 300 PM Sunday...Weakening northeast flow on Wed veers to
southeast Thu as the surface ridge axis shifts offshore. Approach
of weak cold front Thu night and Fri leads to a period of south to
southwest flow but gradient remains weak with speeds staying
around 10 kt. Front pushes off the coast late in the period with
offshore flow setting up Fri night. Lack of cold advection/pinched
gradient will keep speeds under 10 kt. Seas 2 to 3 ft Wed drop to
around 2 ft Thu and Fri.




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