Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 251057
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
657 AM EDT Sun Sep 25 2022

.SYNOPSIS...
Dry with temperatures above normal today followed by a cold
front tonight. Cold air is slow to arrive and temperatures above
normal are expected on Monday. A gradual cooling trend begins
Tuesday and continues through the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Mid-level cloud cover in advance of a cold front will be featured
throughout the day. Layer RH and satellite observations indicate
that the thickness of these cloud will be limited during the
daylight hours which shouldn`t have an impact on high temperatures
today. High pressure shifting offshore will allow for southerly
winds to develop across the region with gusts up to 20 mph along the
coast this afternoon. Afternoon high temperatures likely reaching
the mid 80s.

A weak cold front will approach the area this evening. This front is
associated with an upper low over southern Ontario and is nearly
stalled over the lower Canadian Shield. A shortwave moving through
the Ohio River Valley will be the forcing to push the cold front
across the southern Appalachians late Sunday.

This front is likely to be moisture starved as it progresses
eastward overnight. Model soundings show very little saturation even
ahead of the front when southerly flow and moisture increases. In
addition to the unconvincing moisture profile, forcing seems to be
lacking outside of the weak boundary itself. Winds aloft will remain
fairly zonal and height falls will be limited as a result. As
mentioned in advance of this disturbance, the best forcing seems to
remain well north of the area.

The most likely signal that this front has passed will be a
combination of a surface wind shift and mid level cloud cover. With
the latest forecast update, I have continued the downward trend of
PoPs over southeastern NC (now only a slight chance, around 15-20%)
and kept northeastern SC dry through the overnight period. There
could be some resurgence along the coast ahead of sunrise in the
form of shallow showers influenced by the marine layer over extreme
southeastern NC before sunrise. Dry air will be advecting aloft by
this time, so any showers would be brief, shallow, and light in
intensity if any are able to develop. Overnight lows on the upper
end of guidance due to the cloud cover: low to mid 60s inland, near
70 along the coast.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Large 5h trough building in Mon morning with cold front just
offshore. The trough will remain over the east coast through the
short term. Deep dry air moves in behind the front with precipitable
water around 1 inch on Mon dropping under half an inch Tue following
the passage of a secondary cold front. Forecast soundings depict a
healthy mid-level subsidence inversion developing Mon and persisting
through Tue night. Rainfall chances during the short term appear
very limited at best and more likely to be near zero given the
unfavorable environment. Temperatures end up above climo Mon despite
the passage of a cold front. The combination of morning sun,
southwest flow and the lack of cold advection will keep temperatures
above climo. Flat clouds will develop in the afternoon with moisture
trapped under the inversion. Cold air arrives late Mon with temps
near climo Mon night and Tue. Reinforcing cold air arrives later Tue
dropping lows below to well below climo Tue night.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Uncertainly and Ian will be the main stories of the long term. Ian
appears destined to make landfall along the eastern Gulf Coast, but
the exact location remains very uncertain. This has cascading
affects for the forecast late in the week. Abundant, deep moisture
and the possibility of a stalled front in the area suggest potential
for plenty of rain mid to late week along with abundant cloud cover.
The track of Ian post landfall will also be key in deciphering what
the local impacts will be. Given the low confidence and the large
spread between the various medium rang models and their ensembles
feel the only thing that seems certain is an increase in rain chance
late in the week and lower diurnal temperature swings with clouds
and rain keeping highs below climo and clouds overnight keeping lows
near to above climo. The extent of local impacts from Ian will
become clearer during the next few days, so stay tuned.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
VFR. High pressure shifts offshore today ahead of a cold front
allowing southerly winds increase this afternoon. A cold front
will move through the area overnight with limited moisture.
Small chance of an isolated shower in NC. Mid-level cloud cover
and a weak wind shift from S to SW and W should be the only
signal of this front`s arrival.

Extended Outlook... VFR as high pressure builds through mid-
week.

&&

.MARINE...
Through Tonight:
High pressure moves offshore today ahead of a cold front,
increasing the gradient over the nearshore waters. Souther winds
increase to around 15-20 knots this afternoon with gusts up to
25 knots. Seas will be dominated by the resulting wind wave, up
to 3-4 feel late today and into tonight. Shower chances increase
as the cold front moves offshore overnight and into early
Monday. A few thunderstorms are possible, but widespread shower
activity is not expected.

Through Thursday:
A couple cold fronts will move across the waters early this
week before high pressure builds in from the northwest later Tue
through Thu. Southerly flow on Mon will become offshore,
gradually veering to northeast as the high builds south.
Location and strength of Ian will be key in determining the
strength of the gradient over the waters mid-week which will in
turn affect the strength of northeast flow. Still a lot of
uncertainty with respect to Ian`s eventually track but an
extended period of small craft advisory conditions, at the very
least, seems likely starting Wed. Seas 2 to 3 ft Mon and Tue
will start to build as northeast flow increases Wed. Cannot rule
out seas approaching or exceeding 10 ft depending on where Ian
goes. Seas will be dominated by a southwest wind wave on Mon
before a north and eventually northeast wind wave become
dominant Tue and Wed.

&&

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

&&

$$
SYNOPSIS...ILM
NEAR TERM...21
SHORT TERM...III/LEW
LONG TERM...III/LEW
AVIATION...21
MARINE...III/21


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