Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 200423
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1123 PM EST Mon Feb 19 2018

.SYNOPSIS...
A warm front will move north of the area by mid-morning
Tuesday. Bermuda High pressure will ridge in from the east and
bring temperatures well above normal this week with possible
record warmth Wednesday and Thursday. A cool front will drop
towards the area Friday but likely stalling just to our north.
The Bermuda High will again expand over the region for the
upcoming weekend. A cold front will approach from the northwest
late Sunday night and may stall across the region Monday.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 930 PM Monday...Have raised a Dense Fog Advisory for the
entire ILM CWA, in effect now thru 10 am Tuesday.

Have not had too many opportunities this winter in forecasting
CAD events as well as inland progressions of coastal and warm
fronts respectively.

A coastal warm front had recently pushed onshore and now
extends from Elizabethtown to Florence. With a saturated low
level atm, light to calm winds and a semi-stalled boundary in
the vicinity, areas of fog quickly developed after sunset over
land areas. The fog further dropped to dense criteria
especially across locations that show very limited mid and high
level clouds present. The dense fog remains quite shallow with
the ILM Tower indicating vsby at 6 miles above the sfc based fog
layer. Model guidance and latest sfc obs trends indicate the
patchy dense fog at the moment should transition to areas of
dense fog by midnight and pretty much staying that way possibly
up to mid daytime morning Tue. The area from Little River Inlet
eastward will see occasional isolated light and brief showers
move onshore overnight basically traveling along the periphery
of the expanding Bermuda high. Vsbys may briefly improve but
will drop back to dense criteria. Some tweaks applied to
tonights lows as well as both the hourly temps and dewpoints.

Previous......................................................
As of 3 PM Monday...It`s been easy to find the warm front
today, outlined by a 20-degree difference in temperature and an
almost 180- degree difference in wind direction. The front
pushed onshore across SE North Carolina where Wilmington reached
75 degrees before noon, but temperatures have so far stayed in
the 50s in Florence, Darlington and Lumberton. A persistent
stream of clouds and light showers linked to moisture advecting
in from the Gulf Stream off the South Carolina coast has
produced waves of light showers across Myrtle Beach and up
through Whiteville and Elizabethtown this afternoon. This rain
should weaken with time as it slips into the Cape Fear area
early this evening.

The high-res models have performed quite well with the frontal
position today. The NAM, RUC, and HRRR correctly depicted cool
inland temperatures and northerly wind directions, while the
GFS and ECMWF were rather clueless. All models show shallow low
clouds developing across the entire area tonight as tropical
moisture continues to advect overhead. Stratus clouds may settle
down to the surface becoming fog overnight, perhaps even dense
at times. Although no dense fog advisory will be issued yet,
we`ll highlight the potential in the Hazardous Weather Outlook.
Overall depth of the stratus may be a little too shallow for
drizzle.

The sun should burn through the clouds and fog by late Tuesday
morning, jumping the warm frontal position well inland. As the
nearly tropical airmass, now down at the surface, is warmed by
the sun look for Tuesday`s highs to approach 80 degrees inland.
The beaches may do good to touch 70 degrees for highs with a
relatively cool southerly wind across the ocean. Areas of sea
fog lingering offshore could reach the beaches at times Tuesday
afternoon but should dissipate very quickly after crossing
inland.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 3 PM Monday...Short term to be characterized by
unseasonable warmth. Temperature deviations from climatology
will be about 20 degrees by both day and night making lows
warmer than seasonable highs. As for Wednesdays highs in the
upper 70s coast low 80s inland could be poised to break some
records depending on ocean influence. Record highs for 2/21:

ILM: 78 from 2014.
FLO: 81 from 1997.
CRE: 76 from 1953.

The former appear to be in trouble while CRE will be dealing
with SSE onshore flow of the marine layer. Speaking of the
marine layer, models are still showing areas of sea fog through
a good part of the period. SREF VSBY<1nm probs maxing out over
SC areas and have for a while now and this seems plausible. This
moisture will occasionally affect areas along the Grand Strand
and also make for some temperature forecast complications.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 3 PM Monday...Continues to look like a period of extended
warmth with potential for record breaking temperatures this week.
Bermuda High and 5h western Atlantic ridge team up to bring an
extended period of warm southerly flow and mid-level subsidence.
GFS continues to slowly back away from bringing a backdoor cold
front into the area Thu night and Fri. Meanwhile the Canadian,
ECMWF, and WPC all have the front stalling out around the NC/VA
border. Given the GFS is trending in this direction and mid-
level ridging tends to win out went ahead and removed any hint
of a front moving into the area Thu night and Fri. Next shot at
rainfall looks to be Sun night as cold front moves in from the
northwest. Front lacks a strong cold push and the ECMWF stalls
it in the region while the GFS passes it cleanly. Looking at the
predicted upper pattern would think the front stalled in the
area is probably more likely and for now will carry the Sun
night chance pop through Mon. The dynamics associated with the
front pass northwest of the area and forcing Sun night would be
limited, curtailing rainfall amounts. Might have a better shot
on Mon if the front ends up stalled and shortwave activity can
get involved, but have low confidence for the start of next week
at this point.

Partial thickness and 850 temps through the end of the week
suggest highs in the upper 70s to low 80s for areas not along
the immediate coast. Southeast to south flow will lead to a
strong sea breeze that will become a modified resultant as the
winds veer to south- southwest late in the period. Onshore flow
and water temps in the mid to upper 50s will keep highs at the
beaches in the mid to upper 60s at best. Front moving into the
area Sun night/Mon will drop temps a little. Even so most areas
are likely to end up close to 10 degrees above climo. Lows will
be even warmer with potential for lows 25 degrees or more above
climo.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
As of 00Z...Low confidence forecast. Currently VFR inland
terminals and MVFR with patchy light showers coastal terminals.
KMYR has had tempo bouts of 300-400 foot cigs through the
afternoon until TAF issuance time. This could be indications
sea fog is more persistent than satellite imagery indicates.

Showers will continue at the coastal terminals overnight but
become more isolated. Winds will be very light overnight all
terminals, thus fog is expected to develop. Cloud cover will
help prevent any real dense fog through 06Z, except at
KCRE/KMYR where IFR/LIFR could develop this evening if sea
fog continues to develop and spread. KILM should be far
enough away from the coast to escape the sea fog. After 08Z IFR
conditions are more likely to develop at KFLO/KLBT/KILM and
persist through 14-15Z, with a low possibility of LIFR.

Fog should lift to MVFR by mid morning with VFR by noon. The
exception will be KCRE where sea fog could persist into the
afternoon. Winds will be southeast to south 5-10 kt.

Extended Outlook...VFR. Morning IFR/BR possible Tuesday-Thu. Sea
fog possible through Thu but confidence is low.

&&

.MARINE...
NEAR TERM /THROUGH MONDAY/...
As of 930 PM Monday...Dense sea fog has expanded across the
local waters and as a result a dense fog advisory has been
issued for all waters til noon Tuesday.

Winds and seas will not be the issue for Mariners tonight or the
next few days. It will be the dense sea fog. With SSTs in the
mid 50s and sfc dewpoints in the mid 60s advecting across
theseshelf waters, the outcome is for the development of sea
fog. Satellite imagery, specifically GOES East channel
difference, ie. the 10.3-3.9 micron, illustrates the sea fog
nicely across the local waters as well as the inland fog. And
has become a very helpful tool especially across locations that
do not have a dense network of observations, like the coastal
waters.

Winds generally around 10 kt from the SE-S. And seas 2 to 3 ft
and mainly comprised of 4 to 6 second wind waves.

Previous......................................................
As of 3 PM Monday...A warm front moved across the coastal waters
this morning and has pushed inland across the Cape Fear area.
Variable winds remain along the Grand Strand coastline with the
front still stalled 5-10 miles out, and we don`t really
anticipate seeing solid southeasterly winds develop along the
Grand Strand beaches until late tonight when the front finally
jumps onshore. In terms of model guidance preferences, the NAM
model has been far outperforming the GFS with wind directions
today.

Mainly southeasterly winds should become southerly on Tuesday around
10 knots. Seas 2-3 feet should change little through Tuesday. As
tropical moisture continues to move across the cold nearshore
waters, the potential for areas of sea fog will remain in the
forecast through tonight and Tuesday. The limiting factor with sea
fog may turn out to be the overwhelming warmth of the incoming
airmass, perhaps not allowing the cold water to successfully cool
air down to its dewpoint. No dense fog advisory will be issued at
this time, although some potential does remain.

SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 3 PM Monday...A quiet and unchanging set of conditions
through the period. High pressure off the coast to bring a
southerly wind of just 10kt with a few occasional higher gusts.
Seas will average right around 3 ft.

LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 3 PM Monday...Bermuda High will maintain southerly flow
through the period. Weak backdoor front will try to drop in from
the north Thu night into Fri but appears the boundary will
stall out near the NC/VA border. Gradient will be on the weak
side with winds 5 to 10 kt Thu and Fri. High strengthens a bit
for the weekend with gradient becoming a little more defined as
inland areas warm up. Southwest flow on Sat will be closer to 10
to 15 kt. Seas 2 to 3 ft Thu and Fri build to 3 to 4 ft Sat as
winds become southwest and increase in speed.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Dense Fog Advisory until 10 AM EST Tuesday for SCZ017-023-024-
     032-033-039-054>056-058-059.
NC...Dense Fog Advisory until 10 AM EST Tuesday for NCZ087-096-099-
     105>110.
MARINE...Dense Fog Advisory until noon EST Tuesday for AMZ250-252-254-
     256.

&&

$$
SYNOPSIS...DCH
NEAR TERM...DCH/TRA
SHORT TERM...MBB
LONG TERM...III
AVIATION...MRR



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