Area Forecast Discussion
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FXUS62 KILM 270539
Area Forecast Discussion
National Weather Service Wilmington NC
139 AM EDT Thu Oct 27 2016
Canadian high pressure will lose its grip on the area tonight and
Thursday. A cold front will cross the area and move offshore Friday
morning. High pressure will follow for the weekend with above normal
temperatures expected. Another dry cold front should move across
the area on Monday.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 1230 PM Thursday...Latest IR loops show cirrus increasing
over the forecast area. That, plus the onshore flow, should aid
help keep a floor on temperatures for the rest of the overnight
period. Temperatures now range from around 60 at the beaches to
the lower 50s just a little way inland. Previous discussions
A few tweaks have been made to temperatures as a decoupled
boundary layer over SE North Carolina allowed temperatures to fall
more quickly than expected. Cirrus and 3-5 mph winds in the
Florence-Darlington area and along the immediate South Carolina
coast have held temperatures up higher here. Overall no
significant changes to the forecast with this update. Discussion
from 730 PM follows...
Surface high pressure is centered up over northern Quebec, but
extends a ridge axis all the way down into the Carolinas. The
upper ridge along the east coast will weaken tonight as a
shortwave advances eastward across the Mid- Mississippi Valley
region, and this should cause surface pressures to fall. A heavily
modified Canadian airmass over much of the western Atlantic shows
up as an expansive deck of stratocumulus clouds offshore. As the
surface ridge decays away, veering low- level winds will begin to
advect this moisture onshore, with skies becoming partly cloudy
late this evening over coastal South Carolina, perhaps spreading
northward to encompass the entire area by daybreak Thursday.
A couple of models (12z WRF-NMM and 18z NAM) try to squeeze small
amounts of rain out of this stratocumulus deck overnight. The NAM
appears to erode the impressive subsidence inversion away too
quickly, allowing the moisture depth to increase enough for
showers. I like the GFS soundings which show the inversion
weakening, but remaining intact enough to keep stratocumulus
No significant changes have been made to forecast lows, still
anticipated to reach 50 inland and mid 50s along the coast.
.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...High pressure extending into the
Carolinas will be squeezed out by a weak trough just off shore and
a cold front approaching from the northwest. The weak trough just
off the coast may produce enough convergence through the morning
hours to produce some clouds. Moisture profiles show this
moisture, as well as some mid to high level moisture from system
upstream producing a mainly partly cloudy sky through the morning
hours. The NAM is actually producing a few spotty showers in the
waters just north toward Cape Lookout. By afternoon, expect temps
to soar into the 70s and close to 80 portions of northeast South
Carolina in warm southerly return flow. A westerly flow just above
the surface will also aid in downslope heating. With relatively
cooler water temps in the mid 60s to near 70 expect to see a sea
breeze develop. Convergence along the sea breeze boundary will
produce some aftn cu and therefore expect partly cloudy skies most
of the day tomorrow.
Winds should remain southerly through Thurs night which will
combine with higher dewpoint air and some cloud cover to allow
overnight temps to remain well above normal...55 to 60 most
places. The winds will veer around to the W and then NW to N as
front sinks S-SE through the morning hours on Fri. Not expecting
much in the way of cooler air following the front as ridge builds
in from the west with increasing h5 heights. This will combine
with a warm start to the day on Fri and will offset any CAA to
produce temps well into the 70s once again with a slightly drier
northerly wind. High pressure at the surface will establish
itself over the area into the weekend. Expect clear skies by Fri
night along with a drier airmass following the front and therefore
expect temps to drop into the low to mid 50s.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...Quiet and warm weather to dominate the
extended as ridging builds aloft and high pressure remains dominant
at the surface. The weekend looks beautiful with weak ridging aloft
and an elongated area of high pressure extending east to west across
the southern tier states. This will produce temps about 10 degrees
above climo, and most locations will top out at 80 or better both
Saturday and Sunday. Mins both nights will also be quite warm, about
10-15 degrees above normal for the end of October. A weak impulse
will move overhead Monday early Monday dragging a mostly dry cold
front through the area. Attm will keep mentionable POP confined
north of the CWA, and the FROPA will be identified only by a wind
shift, somewhat increased cloud cover, and slightly cooler temps -
although these may hold off until Tuesday as cold advection lags.
Halloween night will be warm and clear. Ridging amplifies across the
southeast through the middle of next week, but high pressure axis to
the west will keep cool NE winds at the surface, so temps will be
somewhat cooler than this wknd, but still well above climo for the
date. Once again, no measurable precip is seen during the
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
As of 06Z...VFR will continue to dominate the period however,
brief interludes of MVFR fog will be possible at inland terminals
around daybreak. Latest forecast soundings have backed off on the
SCT cloud around 3k ft through the morning hours and instead
trended in favor of the MVFR ground fog.
Winds will remain light with east to southeast winds in the
morning becoming south to southwest in the afternoon. Speeds will
remain 10 kt or less at all terminals. Anticipate development of
SCT to BKN flat cumulus around 5k ft anywhere from late morning to
early afternoon lingering into the evening hours and possibly
overnight. Cold front approaches from the northwest late tonight,
crossing the area Fri morning. Limited moisture return ahead of
the front and overnight timing will prevent shower development.
Winds may shift to northwest as the period comes to an end but
weak gradient and lack of cold advection will keep wind speeds
under 10 kt.
Extended Outlook...VFR expected.
NEAR TERM /THROUGH TONIGHT/...
As of 1230 AM Thursday...Latest obs show seas of right around 2 ft
with easterly winds in the 10 to 15 kt range. This fits in well
with the latest updated forecast, of which there is no change.
Previous discussion follows:
1036 mb high pressure is centered way up over northern Quebec,
but extends a ridge axis all the way into the Carolinas. Pressures
will fall tonight as the ridge decays away. This will allow east-
northeasterly winds to veer more southeasterly with time, with
wind speeds 10-15 kt this evening falling to near 10 knots
overnight. Area buoys report sea heights of 2-3 feet with dominant
periods around 4 seconds. There`s also a small swell at around 8-9
seconds period showing up in spectral wave data from the
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...High pressure will extend into the
Carolinas while a very weak coastal trough develops over the
waters. Overall expect winds to continue to veer from E to SE and
eventually S as a cold front approaches from the northwest. This
front will drop through the waters early Fri with limited CAA in a
light northerly flow. May see an isolated shower or two in the
waters but overall expect just some clouds and a slight uptick in
winds and seas through Fri night. Expect winds 10 to 15 kts
through the period with seas up to 3 ft.
LONG TERM /SATURDAY THROUGH MONDAY/...
As of 300 PM Wednesday...High pressure will slowly move across
the waters during the wknd, followed by a weak cold front which
will cross offshore early Monday. Ahead of this front, the weak
gradient and return flow will create light SW winds of 5-10 kts,
before turning to the N/NE during Monday behind the front with an
increase in speed to 10-15 kts. Seas will be 2-3 ft Sat/Sun with a
SE ground swell and low-amplitude SW wind wave, before a NE short
period wave develops on Monday in continued 2-3 ft seas.