Area Forecast Discussion
Issued by NWS Wilmington, NC
FXUS62 KILM 191039
Area Forecast Discussion
National Weather Service Wilmington NC
639 AM EDT Sun Mar 19 2017
Canadian high pressure will build across the Carolinas today and
tonight, then shift into Florida by Monday night. After a brief
warmup on Tuesday the next cold front will bring showers
Tuesday night followed by much chillier conditions Wednesday
and Thursday. A gradual warming trend is expected late in the
.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Sunday...Cold front moving across the area will exit
stage right early this morning, pushing offshore even Georgetown
county in the next hour or so. Thereafter, the front will move east
as expansive high pressure across the Great Lakes ridges down the
Appalachians and towards the ILM CWA. This ridge axis will likely
remain west of the area through today, and as the gradient remains
pinched behind the front, gusty NW winds are expected through the
day. Forecast profiles show up to 30 kts on RAP/NAM BUFR soundings
at the top of the PBL this aftn, so wind gusts of 20-30 mph are
forecast through the daylight hours. This NW wind is a downslope
direction, which will combine with mostly clear sky conditions to
somewhat offset ongoing CAA. The exception to this will be in NE
zones, where a mid-level vorticity impulse will drop around the
closed low off New England, and off the Outer Banks this aftn. Attm
it appears any precip will remain offshore as best PVA is directed
east of the CWA, but increased cloudiness is possible and have added
some increased sky percentages along and NE of a line from
Elizabethtown to Carolina Beach. Still, have highs on the warm end
of the guidance envelope, low 60s in the Pee Dee, to upper 50s
across Cape Fear.
As the surface high drifts SE tonight, winds will ease towards calm
and temps will plummet beneath good radiational cooling conditions.
A blend of guidance is preferred for mins tonight, which suggests
mid 30s most places, but around 40 at the beach, and some lower 30s
possible in the typical cold spots. Have continued with patchy frost
across a good portion of the area, but will let day shift make a
decision on any frost advisory for tonight.
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...Surface high pressure centered over the
southern Appalachians Monday morning will sink south into
Florida by Monday night. With full sunshine Monday and warm
advection (850 mb temps rise from +2C to +8C during the day)
highs should reach the upper 60s across the Pee Dee region with
60-63 on the coast. Westerly flow aloft will advect in moisture
late Monday night with clouds increasing late. I`m not sold on
any precip making it this far east despite the .01 QPF contour
on both the ECMWF and GFS very close to Bennettsville and
Lumberton before 12z Tuesday. Forecast soundings show cloud
bases ~11,000 feet and insufficient lift in my opinion to get
measurable precip down to the ground.
The airmass really modifies on Tuesday as west-southwest flow
continues between the high down over Florida and a cold front
dropping south across the central Appalachians and Ohio Valley.
Assuming there`s enough sunshine, 850 mb temps up to +12C could
allow highs to reach 80 in the SC Pee Dee region, with low to
mid 70s along the coast.
The approach of a shortwave trough Tuesday evening coupled with
weak instability and an increasing depth of moisture should
yield a wave of showers and thunderstorms, most concentrated
across SE North Carolina like in the Saturday night event we
just had. The actual surface cold front has slowed down in the
models. (last night`s ECMWF was the first to suggest this)
The front may only reach Cape Fear by sunrise Wednesday
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 300 AM Sunday...A surface cold front should be traversing
the area Wednesday morning, pushing all the way down to
Charleston by lunchtime. Shallow cold air surging south behind
the front coupled with a moist westerly flow over the top of the
frontal surface means Wednesday could remain cloudy with patches
of light rain or sprinkles. By Wednesday evening the mid level
flow should veer more northerly, dragging in enough dry air to
dissipate the post-frontal clouds. Unfortunately this means
radiational cooling within the chilly airmass could create
headaches with frost or even a mild freeze by Thursday morning.
Model ensembles still show enough spread in forecast low-level
temperature/moisture for Wednesday night/Thursday morning that
I don`t have high confidence, but it definitely bears watching.
Surface high pressure moving across the Great Lakes Wednesday
night and Thursday will move off the East Coast late Thursday
night. Veering low-level winds will modify our airmass Friday
and Saturday with rising temperatures and dewpoints. Precip
chances may increase Saturday as the next synoptic frontal
systems approaches from the west.
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
As of 12Z...Clear skies will predominate over the next 24
hours...with the only exception across far-eastern North
Carolina including the Wilmington airport (ILM) where scattered
to occasionally broken cold-air cumulus with bases as low as
4000 feet should develop. Breezy northwest winds with gusts up
to 23-26 knots are expected during the daylight hours,
diminishing to less than 10 kt tonight.
Extended outlook...VFR expected through the period except for
possible MVFR/IFR conditions from low ceilings and pcpn ahead
of the next cold front Tuesday night into Wednesday.
NEAR TERM /THROUGH SUNDAY/...
As of 300 Am Sunday...Cold front moving off the coast this morning
will push through the coastal waters through daybreak, leaving gusty
NW winds in its wake. Strongest of these winds are expected through
late morning behind the front, with a slow decline in speed forecast
by evening as high pressure begins to build towards the area. West
winds first thing this morning will quickly become NW in the next
few hours, and then increase to 20-25 kts with higher gusts,
persisting above SCA thresholds into this evening. The ongoing SCA
has been extended through this evening for the winds, even as seas
fall from 4-6 ft most of today to 3-4 ft on thee offshore winds this
evening. Winds will ease further tonight and veer to the North as
elongated high pressure builds down the coast, and by Monday morning
North winds of 10-15 kts will be common across the waters, producing
seas of 2-4 ft.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 AM Sunday...High pressure centered over the southern
Appalachians Monday morning will drop south into Florida by
Monday night. With the reorientation of the ridge, our winds
will back from northwest to southwest. By Tuesday night, a cold
front dropping south through the Ohio Valley and central
Appalachians will move into North Carolina. Yesterday`s ECMWF
model may have been correct after all as more models are slowing
down their depiction of this front as it approaches the area.
Our latest forecast now shows the wind shift reaching Cape Fear
around sunrise Wednesday morning.
LONG TERM /WEDNESDAY THROUGH THURSDAY/...
As of 300 AM Sunday...A wave of low pressure moving off the
North Carolina coast early Wednesday morning will kick a cold
front southward. Latest model projections show the boundary
passing by Cape Fear around sunrise and blowing clear through
Charleston by noon. Breezy northeast winds behind the front will
probably lead to Small Craft Advisory conditions Wednesday
MARINE...Small Craft Advisory until 6 PM EDT this evening for AMZ250-