Area Forecast Discussion
Issued by NWS Wilmington, NC-- Remove Highlighting --
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FXUS62 KILM 200117
Area Forecast Discussion
National Weather Service Wilmington NC
917 PM EDT Wed Apr 19 2017
-- Changed Discussion --A stalled and diffuse front in the vicinity of Charleston SC,
will slowly dissipate as it tries to lift north as a warm front
late tonight and Thursday. The Bermuda High will expand west
over the region Thursday through Saturday. A low pressure system
and associated cold front will move through the Carolinas late
Sunday into Monday, with low pressure possibly lingering off
the U.S. Southeast coast thru Tuesday. High pressure will build
in slowly behind departing low Tuesday through Wednesday.
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.NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --As of 845 PM Wednesday...The sea breeze induced convection has
dwindled to just isolated showers at the moment, and should be
all clear within the the next 1 hour. Convective debris
cloudiness will thin or scour out during the remainder of this
evening and overnight. This will allow for radiational type fog
to develop especially across areas having received rainfall
today. The problem facing the FA overnight will be the extent of
the fog and whether it reaches dense criteria. And a side note,
of whether low level stratus develops. For now, have followed
previous thinking with fog at its worse inland. Will remain
somewhat suspect of the low stratus deck, but if it occurs it
should be around 1.5k ft or lower. Low temps tonight look aok
with no tweaking needed.
As of 300 PM Wednesday...Fairly widespread shower activity has lit
up just inland from the coast along the seabreeze front. This
activity has developed within an uncapped airmass with CAPE around
1000 J/kg and very little steering flow. Showers should exhaust
their fuel in the next several hours and dissipate with the setting
of the sun.
A weak and diffuse front stalled across southern South Carolina
should begin to move northward tonight as high pressure over the
Canadian maritime provinces pulls off to the northeast. This
boundary will move overhead between midnight and 5 AM, however winds
here at the surface should be decoupled and we won`t immediate
notice the front`s passage. Another consequence of the decoupled
boundary layer tonight is likely to be fog. Moisture advection with
today`s onshore flow plus this afternoon`s shower activity should
yield areas of fog by midnight. Fog could become dense at times,
although the shallow depth of the decoupled boundary layer argues
for a quick burnoff Thursday morning.
Thursday will seem almost summerlike with light southwest winds and
mainly sunny conditions in the morning turning partly cloudy and
warm with scattered showers during the afternoon. A moderate
seabreeze circulation should develop, helping to concentrate showers
essentially over the same regions that have picked up rain today. A
somewhat stronger west-northwesterly mid level flow could help push
showers across the seabreeze and back down toward the beaches by
late afternoon, and I have included PoPs as high as 30 percent for
Wilmington and Myrtle Beach as as result. Highs Thursday should
reach the mid 80s inland with upper 70s to lower 80s at the coast.
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.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...Potentially the hottest temperatures so far
of 2017 expected Friday as low-amplitude but strong ridge builds
across the southeast. Surface high offshore will create warm SW
return flow, driving 850mb temps up towards 14C Friday. This occurs
in conjunction with W/NW mid and upper level flow, which is
typically a dry and warm flow aloft, further adding to the heat
potential. The MOS guidance is all within a degree or so, and expect
widespread mid-80s with upper 80s across the Pee Dee. In fact, a few
spots may touch 90 well inland for the first time this year. ALong
the coast, a sea breeze will develop but not before most places at
least touch 80, the exception being the typically cooler Brunswick
County coast where highs will struggle into the mid 70s. The same
airmass responsible for this heat will keep mins elevated both
Thursday night and Friday night as well, dropping only to a degree
or two either side of 65 both nights.
A cold front will approach slowly from the NW late Friday night, but
most of the guidance suggests it will hold off until beyond this
period before creating any showers or even much in the way of cloud
cover. Feel this slower solution is more likely as its motion gets
impeded both by boundary parallel mid-level flow, as well as
orthogonal surface flow impinging on the front from the south, and
will drop POP to silent until very late Friday night, and even then
only include SCHC for far NW zones.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...Deep southerly return flow around the
Bermuda High with ridge aloft will bring very warm weather for
the weekend. The models have been consistently showing a
backdoor cold front reaching into NC and may be nearby early Sat
with the GFS being the most aggressive with the southward push.
It looks like this boundary should remain far enough north as
to keep most associated weather north of the forecast area for
now. A low pressure system moving west through the southern
CONUS will push this front back north by late Sat into Sun
leaving the coastal Carolinas in a continued warm and moist
south to southwesterly flow. Pcp water values along this front
to the north will be up to 1.6 inches but down near 1.25 inches
in most of our local forecast area through Sat and diminishing
further through early Sun. Overall expect the development of
some cu and potential for localized showers on Saturday if
boundary stays north, but will include clouds and pcp over
northern tier to account for front in vicinity.
Sunday should start off dry with increasing clouds through late
Sunday as cold front approaches from the west. Best chc of
showers and thunderstorms will come late Sunday west zones and
into Sunday night for coast, but should be fairly widespread
coverage with strong to possible severe storms in a very warm
and moist air mass ahead of front. Cooler northerly flow will
advect drier air into the area on the back end of the low, but
the low will linger right off the coast with clouds and pcp
remaining on Monday and possibly into Tues. The greatest chc for
pcp will be closer to the coast especially as the low pulls
slowly away late Mon into Tues. Drier high pressure will build
in behind the departing low Tues into Wed.
Temps will reach into the 80s except right along the coast both
Sat and Sun, but Mon will cool down to near 70. A slight warming
will occur through mid week bringing temps up near normal again.
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
As of 00Z...The sea breeze induced convection will pretty much
come to an end once sunset occurs and nightfall settles in.
Will include VCSH for LBT terminal based on the latest 88D pcpn
trends. Convective debris clouds will dominate the evening sky
but should dissipate or scour out quickly during this evening.
The next obstacle to tackle for aviators during the pre-dawn Thu
hours will be the potential for fog and how widespread and deep
in the vertical will it become. With increasing moisture in the
lower levels and winds becoming nearly calm across all
terminals, radiational type fog looks like a good bet. With
leftover convective debris clouds scouring out by midnight,
will indicate fog developing there-after and persisting up to
1-2 hrs after daybreak. The inland terminals will potentially
see dense fog during the pre-dawn hrs. For the coastal
terminals, took the more optimistic route and kept the dense fog
possibility out of the fcst, for now. CRE terminal always likes
to go against guidance when it comes to fog possibilities, and
it`s usually for the worst case scenario. For now, will indicate
down to 2sm.
For daylight Thu, will see another sea breeze induced convection
day. It`s inland progression may be limited and thus held out
from mentioning any convection for the 2 inland terminals.
The center of high pressure overhead tonight will become re-
established offshore from the SE U.S. coast on Thu. Looking at
nearly calm winds tonight becoming W to SW during Thu. A light
increase to the sfc pg will result in 5 to 10 kt sustained winds
Extended outlook...MVFR/IFR conditions possible in showers and
TSTMS Saturday through Sunday night.
-- Changed Discussion --NEAR TERM /THROUGH THURSDAY/...
As of 845 PM Wednesday...Winds from Cape Fear northward remain
active from the E around 10 kt. South of the Cape, southeast to
south at 10 kt or less. Winds overall will be veering as the
elongated center of high pressure overhead, becomes
re-established offshore from the SE U.S. Coast by late Thu. The
sfc pg remains relaxed tonight and shows signs of some
tightening during Thu. Significant seas overnight will range
from 3 to 4 ft from Cape Fear northward, with 2 to 3 ft south of
the Cape to South Santee River. An easterly psuedo swell at 7
to 8 second periods will be the primary input for the
As of 300 PM Wednesday...A weak front stalled across
southern South Carolina will weaken as it lifts northward
tonight. Easterly winds blowing as hard as 15 knots north of
Myrtle Beach through the Cape Fear area this afternoon will
settle back to only 5-10 knots as the front approaches around
midnight, then should shift southwesterly late tonight into
Thursday morning. This is all occurring as Canadian high
pressure ridging down the East Coast begins to retreat off to
the northeast. Wave heights have been kicked up in the Cape Fear
area due to the stronger easterly winds in place most of the
day. Frying Pan Shoals buoy is still reporting 6 feet, with 3-4
feet at the nearshore buoys.
Thursday will feature an almost-summerlike pattern as light
southwesterly winds during the morning increase substantially during
the afternoon as a healthy seabreeze circulation develops.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... As of 300
PM Wednesday...High pressure offshore and a slowly approaching
cold front from the NW will drive increasing SW winds through
the period. Wind speeds Thursday night of 10-15 kts will
increase through Friday, becoming 15-20 kts late in the period.
Although an easterly swell from a distant subtropical
depression, and a SE swell around the high pressure, will exist
in the spectrum through the period, it will be increasingly
masked by an amplifying SW wind wave. This wind wave will grow
to 3-4 ft at 5 sec, and wave heights build from around 2 ft
Thursday night, to 3-4 ft Friday night.
LONG TERM /SATURDAY THROUGH MONDAY/...
As of 300 PM Wednesday...South to southwesterly flow will
persist around Bermuda High through the weekend. This southerly
push will drive seas up to 3 to 5 ft late Sat into Sun. Wind
speeds should be about 10 to 15 knots with a slight uptick and
backing of winds each afternoon in sea breeze.
A low pressure system and associated cold front will approach
late Sunday into Sunday night. Winds will shift to the north
behind the front and may increase up to 20 kts or so on the back
end of this low as it lingers and begins to slowly depart Mon
night. This northerly surge may produce small craft advisory
conditions by late Mon.
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