Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 181340
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
940 AM EDT Sun Apr 18 2021

.SYNOPSIS...
Dry and warm weather today. Weak low pressure moving south of
Cape Fear will bring small rain chances to coastal SE NC Monday,
with another chance of rain along the coast late Tuesday. A dry
cold front will across Wednesday, with cool and dry high
pressure moving in Thursday and Friday. A storm system will
approach from the Gulf Coast states on Saturday.

&&

.UPDATE...
Hi-resolution models are still holding on to a few showers along
the sea breeze this afternoon, but have trended PoPs downward
again as the environment will likely struggle to develop any
precip. Dry air in multiple layers of the atmosphere combined
with a fairly strong subsidence inversion should prove to be a
difficult obstacle. No significant changes to temperatures or
winds.

&&

.NEAR TERM /THROUGH MONDAY/...
Split flow continues through the near term and is at least
partly responsible for the trouble much of the guidance has been
having. Not sure any wet stuff will fall from the sky through
the remainder of the overnight into Sun AM. Only chance looks to
be brushing the Georgetown coast and even this seems unlikely.
Dry air can be found in abundance and there is a weak mid-level
subsidence inversion to boot. Front lingers well off the coast
today, laying parallel to the flow aloft. Following the passage
of this morning`s surface wave there will be a lack of any
noteworthy surface features. A lot of the guidance is insisting
on some weak convection developing near the sea breeze
inflection point over northern Brunswick and eastern Columbus
counties then drifting east-northeast. Not really confident in
any showers developing. Forecast soundings are not very
favorable. Lots of dry air below 5k ft, the depth of moisture is
less than 2k ft and the subsidence inversion will keep things
capped under 9k ft. Even if the inversion could be overcome,
deep dry air (large areas of RH under 30%) will be a major
limiting factor. Have not gone for any mentionable pop for this
afternoon/evening given the guidance`s recent propensity for
overdoing rain chances. Partial thickness values this afternoon
suggest today will be a little warmer than Sat. Sea breeze will
still have an effect along the immediate coast, with these areas
once again struggling to reach 70.

Deep west-southwest flow continues tonight, becoming a little
more westerly on Mon. Moisture is limited Sun night and Mon with
the persistent subsidence inversion around 700mb lingering
through Mon. Varying amounts of moisture above 500 mb Sun night
will result in partly to mostly cloudy skies, but the region
will remain dry. Have less confidence in rainfall chances Mon.
Shortwave passing the area to the north may be close enough to
have some influence locally, mainly the northernmost parts of
the forecast area. However, previously mentioned air mass
factors remain a stumbling block. Not quite ready to pull pop
from the forecast but did trend numbers down a bit. Lows will
run above climo Sun night with high near to slightly above climo
Mon.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
Mostly dry and warm for the short term period. Low pressure off
NC coast will continue moving northeastward. Brief northerly
flow will make way for weak onshore winds Tuesday afternoon as
high pressure develops offshore. Combined with a 500mb shortwave
moving across the southeast coast, have maintained low end pops
for Tuesday afternoon and night for southern and coastal areas.
Soundings however have remained pretty dry across the area and
do not expect anything more than widely scattered light
showers, if that. Lows Monday night around 50 warming to upper
70s for Tuesday with scattered cloud cover. Mid 50s expected
Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Low pressure will be deepening over the Ohio River Valley
Tuesday night. As this low moves across the New England region
on Wednesday, it will push a decent cold front across our area
Wednesday afternoon. Moisture will be hard to come by, with bulk
remaining well to the north, and so expect front to be dry with
only a few clouds. Southwest winds will be breezy Wednesday
afternoon, remaining elevated overnight behind the front. Expect
temps and dewpoints to drop quickly behind the front into
Wednesday night.

High pressure will maintain cool and dry conditions Thursday
and Friday, with a weak surface trough moving across Thursday
night associated with a strong 500mb trough. RHs expected to
drop into low 20s Thursday. Wind gusts are currently forecasted
between 15-20 mph, but could see higher gusts if we warm up
enough to tap into stronger winds aloft, which could lead to
fire weather concerns. Next storm system approaches from the
Gulf states on Saturday. Warm temps Wednesday will drop to well
below normal temps for Wednesday night through Thursday night.
Temps slowly rebound beginning Friday.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR conditions will continue through the next 24 hours.
Widespread BKN/OVC ceilings will start to break up during the
morning hours as weak low passing off the coast moves farther
northeast. Inland SC terminals will see SCT conditions
developing by mid-morning with coastal NC taking the longest,
early afternoon. There are hints some weak showers will develop
along the sea breeze, potentially affecting ILM between 18-20Z,
but have low confidence in this. Winds will be under 10 kt with
direction changeable, especially along the coast where a sea
breeze will develop. Winds calm by sunset. May have some MVFR
fog that develops towards the end of the period near KILM, KCRE,
and KMYR.

Extended Outlook...VFR, with occasional middle and high clouds
as several weak waves traverse the region. A moderately strong
cold front Wednesday night may bring restrictions.

&&

.MARINE...
Through Monday: Weak gradient in place through Mon with
boundary stalled off the coast and weak sea breeze developing
each afternoon. Series of ill- defined waves moving along the
stalled boundary will lead to varying wind directions as each
passes. Lack of any gradient will keep speeds under 10 kt, so
while winds will be varying a lot, the winds will have minimal
impact on the waters. Light and frequently changing winds will
keep seas 1 to 2 ft.

Monday Night through Thursday...Northeast winds less than 10
kts Monday night behind exiting low will slowly veer to onshore
winds during the day Tuesday. Seas around 2 ft. Weak southerly
winds Tuesday night will quickly increase to 15kt SW winds by
Wednesday afternoon ahead of an approaching cold front. Seas 2-3
ft Tuesday night through Wednesday afternoon. 15-20 kt SW winds
late Wednesday afternoon will become northwesterly behind the
front Wednesday evening, sustained around 20 kts with gusts
around 25 kts. Brief Small Craft Advisory possible Wednesday
evening through early Thursday morning for elevated winds. Seas
3-4 ft late Wednesday afternoon through Thursday morning, with 5
footers possible in outer coastal waters. Winds weaken Thursday
to 10-15 kts from the WNW as seas lower to 2-3 ft.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$

SYNOPSIS...ILM
UPDATE...21
NEAR TERM...III
SHORT TERM...VAO
LONG TERM...VAO
AVIATION...IGB
MARINE...III/VAO


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