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118
FXUS62 KILM 210150
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
950 PM EDT Sun Oct 20 2019

.SYNOPSIS...
A weak ridge of high pressure will build south
across the Carolinas tonight and Monday with dry weather
expected. A cold front will move through the area Tuesday
bringing a chance of showers and thunderstorms. High pressure and
dry weather are expected Wednesday and Thursday, but rain
chances may increase next weekend as a cold front approaches from
the west.

&&

.UPDATE...
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Forecast updated to cancel Small Craft Advisory over SC coastal
waters where seas have dropped to below 6 ft. The headline remains
until 1 am over NC coastal waters.
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&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
Cooler and drier high pressure will continue to build in behind
Post-tropical Cyclone Nestor as it continues to track off to the
northeast through tonight. A few light sprinkles right along the
shallow frontal boundary will diminish as the front tracks off to
the east leaving behind shallow cool and moist layer. The gusty
W-NW downslope flow should help to break up the clouds a bit, but
soundings and moisture profile show a steep frontal inversion
keeping very shallow moist layer across the area tonight. This is
always tough to break and tough to forecast how long it will
last. Will show some breaks from SW to NE as drier air wraps
around the back side of low through early this eve. But will also
maintain fairly widespread stratus around the area for tonight
and possibly lasting through much of the day on Monday as cooler
and drier air settles in with shallow residual moisture socked in
under inversion.

CAA behind front will keep an overall cooling trend in temps
with most temps right around 60 by this eve. The overnight lows
will be tougher, with most models showing a decent break in
clouds through the first part of the night allowing temps to drop
and then stratus layer should help level them off with some
shallow CAA continuing. Lingering shallow moisture into Monday
will maintain some low stratus but should see increasing sunshine
through the day. Temps will be in the low to mid 50s tonight and
highs Monday in the low to mid 70s. Temps may not reach that
high if clouds hold on.

By Mon night, winds will veer around to the SE to S with warm
and moister flow ahead of approaching cold front. Expect clouds
to increase and thicken after midnight, with showers moving in by
morning. Temps will be warmer with overnight lows remaining in
the 60s.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
Models have come into pretty good agreement that low pressure
over the Great Lakes will push a cold front eastward and across
the Carolinas late Tuesday afternoon into Tuesday evening. The
best vorticity associated with the 500 mb trough will pass to our
north across the central Appalachians, but there should be
enough instability and deep-layer moisture for showers to become
likely. Modest lapse rates should keep CAPE at or below 1000 J/kg
despite high temps expected to reach the lower 80s, but 0-6 km
shear over 40 kt should still promote some multicell organization
of scattered thunderstorms. SPC has the area outlooked in a 5
percent severe risk for wind on Tuesday.

Dry air will build in behind the front Tuesday night with skies
gradually clearing overnight. Lows 50 inland and mid 50s on the
coast.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Confidence is high that Wednesday and Thursday will have nice
weather conditions. High pressure over the Deep South on
Wednesday will move east across the Carolinas Wednesday night,
then offshore on Thursday. Mainly clear skies are expected with
highs around 70 on Wednesday and in the lower 70s Thursday. Lows
in the 40s Wednesday night and 50s Thursday night.

Forecast confidence has become much lower for late in the week
as strong shortwave energy dives south across the Rockies on
Thursday. The 12z GFS wants this energy to remain progressive and
shows a full-latitude trough racing across the country and off
the East Coast Saturday night. The 12z Canadian along with the
00z and 12z runs of the ECMWF cut the shortwave energy off across
New Mexico and Texas on Friday, leading to a much slower
evolution of downstream effects across the Carolinas.

I`ve reduced our forecast PoPs Friday and Saturday versus
forecasts we had our 24 hours ago, but realize there is no
obviously correct answer just yet with how this pattern will
evolve. All models show enough onshore low-level flow off the
Atlantic Friday and Saturday that I can show gradually warming
temperatures into the weekend with rising dewpoints, but I`m
keeping PoPs just a little above climo averages until some
certainty evolves in this weather pattern.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Stratus behind a cold front will move eastward over the next few
hours leading to clear skies and VFR conditions across the area. NW
winds will weaken and become calm. This, along with saturated soils
from yesterday`s rainfall will lead to the development of inland fog
and coastal stratus tonight. IFR conditions are likely to develop
for brief period tomorrow morning at many of the forecast sites. Few
or scattered VFR cumulus to develop tomorrow afternoon with decent
boundary layer moisture.

Extended Outlook...Chance for early morning fog/stratus Tuesday
morning. Cold front expected to move through Tuesday
afternoon/evening with VFR conditions following.

&&

.MARINE...
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Small Craft Advisory extended until 1 am over NC coastal waters
only as seas gradually lower this evening, from 4 to 7 ft down
to 3 to 6 after midnight.

Weak high pressure will build in behind Post-tropical Cyclone
Nestor, as it tracks off to the northeast away from waters. Gusty
W-NW winds on the back end will veer around to the N-NW and
lighten to 10 to 15 kts through tonight and will continue to veer
around to the NE to E through late Mon and eventually southerly
by late Mon night ahead of approaching cold front. Seas will
remain 2 to 4 ft most of Mon through Mon night.

Shower and thunderstorm chances will increase on Tuesday as a
cold front approaches from the west. Latest models increase S to
SW winds to around 15 knots on Tuesday with seas building to
around 4 feet. The front will move offshore Tuesday evening. High
pressure over the Gulf Coast will build eastward Wednesday,
crossing overhead Wednesday night, then moving offshore Thursday.
This should lead to a period of strong offshore winds near 20
knots Tuesday night, then lighter and veering winds Wednesday
through Thursday.

The 12z GFS model may be an outlier with how quickly it brings
the next cold front eastward on Friday. The slower Canadian and
ECMWF models maintain lighter onshore winds during the day
Friday.
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&&

.ILM WATCHES/WARNINGS/ADVISORIES...
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SC...None.
NC...None.
MARINE...Small Craft Advisory until 1 AM EDT Monday for AMZ250-252.
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&&

$$
SYNOPSIS...TRA
UPDATE...MAS
NEAR TERM...RGZ
SHORT TERM...TRA
LONG TERM...TRA
AVIATION...MAS/21
MARINE...TRA/MAS/RGZ