Area Forecast Discussion
Issued by NWS Wilmington, NC
FXUS62 KILM 222344
Area Forecast Discussion
National Weather Service Wilmington NC
744 PM EDT Sat Oct 22 2016
Seasonably cool weather will continue Sunday followed by a brief
warm-up Monday. A reinforcing shot of dry and cool air Monday
night will set the stage for dry weather and seasonable
temperatures for much of the upcoming week. A low pressure system
will approach the area late next week.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 730 PM Saturday...Very few changes were needed to the
forecast with this early evening update. Reduced wind speed
forecasts overnight as it appears most of NE South Carolina away
from the beaches should be able to decouple the boundary layer
before daybreak. 975-950 mb wind speeds hanging around 20 knots
over SE North Carolina may help keep a few knots of wind at the
surface here. No significant impact on overnight temps. Tonight is
still expected to be the coldest night we`ve seen since April 18th
when morning lows included 41 in Wilmington, 42 in Florence, and
41 in North Myrtle Beach. Discussion from 300 PM follows...
Low level jetting and surface pressure gradient continue to relax
and the breeziness seen across the area due to deep mixing will
abate close to sunset. Clear skies and light (but not calm) winds
will allow places to radiate into the lower 40s according to
tightly clustered MOS guidance numbers.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...Although tomorrow will only be a few
degrees milder than today it will feel moreso due to the lack of
today`s gusty breezes. The center of the surface ridge ends up to
our south by evening at which time we will see a light S to SW
wind. Boundary layer temperatures will be recovering so Sunday
night lows will be in the mid to upper 40s despite the continued
light winds and clear sky. Warm advection strengthens on Monday
ahead of a cold front and afternoon temps should shoot nicely into
the upper 70s. This moisture-starved boundary comes through Monday
evening. The gusto of its cold advection will not match that of
the previous cold front keeping Monday night`s lows seasonable.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 300 PM Saturday...Surface high building in from the north
at the start of the period will gradually shift east during the
week. Cool northeast flow at the surface Tue and Wed will veer to
southeast Thu as the ridge axis moves off the coast. At this point
the forecast becomes less clear due to uncertainty with respect to
the evolution of the upper pattern. Early in the week 5h trough
lifts northeast and weak ridge builds east. Period of ridging is
short lived and by Thu afternoon/evening the 5h shortwave ridge
will be replaced by troughing associated with 5h shortwave
crossing the Great Lake/OH Valley regions.
The uncertainty during the second half of the period stems from the
strength of the 5h trough Thu/Fri. Both GFS/ECMWF solutions drive a
cold front into the area late Thu night or Fri but the amount of
forcing and moisture differs. GFS is less amplified and drier while
the ECMWF is showing more amplification of the 5h trough and
increased moisture as well as much better precip chances. Compromise
between the 2 solutions matches up well with the inherited forecast
as well as the offerings from WPC so for now will continue to carry
slight chc to low chc pop Late Thu and Fri with drier and slightly
cooler conditions for Sat. However, temps Sat would still be above
normal as both solutions lack strong cold advection.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 00Z...High confidence in VFR through the valid TAF period.
Winds will try to decouple, however we will probably see 3-5 kts
through the overnight hours. High pressure centered to our west
will give us predominately northwest flow on Sunday, becoming
southerly along the coast with the resultant in the afternoon.
NEAR TERM /THROUGH TONIGHT/...
As of 730 PM Saturday...Small Craft Advisory was dropped at 5 PM
as wind speeds were 20 kt or less and seas were 4 feet or less at
all area buoys, including the Frying Pan Shoals buoy outside of
the coastal waters. While wind speeds should hang in the 15-20 kt
range much of the night there are no 25 kt wind speeds anticipated
to move through the marine boundary layer tonight even at
1000-2000 feet above the ocean`s surface.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...Wind and seas subside a bit early Sunday
as the ridge axis moves across but then picks up later in the day.
At this time no advisories or even cautionary headlines appear
necessary. Monday brings back a diminishing trend as the surface
trough associated with a cold front becomes rather diffuse,
weakening the gradient. FROPA will bring a sharp veer to N or NNE
but not a significant surge, again precluding any headlines.
LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 300 PM Saturday...Pinched gradient Tue morning in the wake
of the exiting cold front will keep northeast flow 15 to 20 kt
into Wed. Gradient slowly relaxes and by Wed northwest winds will
be 10 to 15 kt. Surface ridge axis shifts off the coast Thu with
winds veering to southeast. Gradient remains light with speeds
staying around 10 kt. Seas 2 to 4 ft Tue and Wed drop to 2 to 3 ft