Area Forecast Discussion
Issued by NWS Wilmington, NC

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393
FXUS62 KILM 191643
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
1143 AM EST Mon Feb 19 2018

.SYNOPSIS...
A warm front should move onshore today, but may take until
tonight through move fully across the area. Bermuda High
pressure building in from the east will bring temperatures well
above normal this week with possible record warmth Wednesday
and Thursday. A cold front will likely stall to our north on
Friday. The Bermuda High will again expand over the region for
the weekend. A cold front will approach from the northwest
Sunday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1140 AM Monday...Quick update to lower forecast high
temperatures another couple of degrees from Florence, Marion,
and Myrtle Beach northwestward toward Lumberton and
Bennettsville. While this is due to slower motion of the warm
front northward inland, along the coast it`s due to a persist
streamer of low clouds pushing in from the Gulf Stream off the
South Carolina coast that`s obscuring the sky quite well over
the Grand Strand. If we`re going to get sea fog it should star
to show itself shortly as dewpoints are exceeding 60 degrees on
the coast now. Discussion from 945 AM follows...

Although all land stations still have northeasterly winds
currently, the warm front isn`t too far from the coast given
southeast winds reported as close as 30-35 miles from shore at
Frying Pan Shoals buoy and CORMP buoy 41037.

As you might imagine, models still show a variety of differing
solutions with how quickly the front jumps onshore and how far
inland and northward it progresses during the day. The 06Z GFS
represents the extreme aggressive case for the warm front`s
movement, whipping the boundary through virtually the entire
area this afternoon. The 06Z NAM and latest several runs of the
HRRR represent the other extreme with a stubborn, dense and
cold airmass inland resisting the front`s movement until late
tonight. The truth probably lies closer, but not entirely,
toward the slower progression of the front. I`ve tightened the
forecast temperature gradient across the area this afternoon,
adding a degree in spots near the coast and subtracting a couple
of degrees across Bennettsville and the northern halves of
Darlington and Robeson counties. This yields highs in the mid
60s across Darlington, Bennettsville and northern Robeson
county, and 70-75 degrees for most locations east of I-95. The
beaches should have highs stuck in the 60s given onshore winds
crossing cold water.

Dewpoints climbing into the 60s near the coast this afternoon
may develop some sea fog, particularly near the Grand Strand
where water temperatures are coldest. CCU and NDBC pier
observations show water temps of 53-55 degrees along the
beaches. Discussion from 300 AM follows...

High pressure extends down into the Carolinas from the center
just off the Mid Atlantic coast while a coastal trough/warm
front remains aligned just off the Carolinas coast. Some patchy
drizzle, light rain and fog was over inland areas where weak
isentropic lift exists while some light showers were breaking
out along coastal trough just off the Cape Fear coast. Overall,
shallow moisture with low stratus and patchy fog was holding on
with a well defined near surface based inversion present.

This coastal warm front will push inland and north through this
afternoon with winds shifting around to the southeast to south.
All guidance is showing some breaks in the clouds expected
through this afternoon as inversion breaks. Warm and moist air
will follow as a southerly return flow sets up and ridge builds
aloft. Temps will rise quite rapidly through the 60s but a
fairly sharp gradient will exist as you move inland before the
warm front moves through. A fairly wide spread in guidance
exists with the NAM slower in pushing warm front through and
holding on to temps closer to 60 for highs in the I-95 corridor,
while the GFS has temps reaching 70. For now, have forecast
max temps just above 70 east of I-95 while places along and
west reaching into the mid 60s. Expect some spotty showers
associated with the coastal trough/warm front and have included
mainly iso shwrs with best chc along the coast and offshore.
Not including much in terms of measurable pcp.

Dewpoint temps will follow suit into this evening and expect
widespread fog and stratus to develop heading into this evening
and overnight. Have included patchy to areas of fog into
tonight. This warm and moist airmass will support overnight lows
closer to 60 in most places with some mid 50s further inland.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM Monday...Unseasonably warm temperatures are
expected in the wake of a warm front as a strong Western
Atlantic Ridge builds across the waters. Temperatures at 850 mb
are forecast to be 12-15C through the period. Subsidence and
only very shallow moisture should prevent any showers from
developing. However, model soundings continue to portray a
favorable profile for at least patchy late night and early
morning fog/stratus. Also, with dewpoints in the lower to mid
60s through the period, any sea fog that does develop could
periodically impact some of the beaches at any point in the day
or night.

Highs will be well up in the 70s Tue and a couple 80 degree
readings are possible well inland. Highs on Wed will be similar
if not a degree or two higher. The seabreeze circulation should
be strengthening each afternoon and thus there should be a sharp
temp gradient near the coast with high temps at the beaches
stymied near or just above 70 degrees each afternoon. Lows each
night will be commonly in the lower 60s.

Record highs could be challenged on Wed...

02/20
City               High Temperature Forecast/Daily Record High

Wilmington         76/81 in 1991

Florence           79/83 in 2014

N Myrtle Beach     72/77 in 1949

02/21
City               High Temperature Forecast/Daily Record High

Wilmington         77/78 in 2014

Florence           82/81 in 1997

N Myrtle Beach     72/76 in 1953

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 300 PM Sunday...Main theme for the extended will be
strong surface and mid-level ridging sitting off the coast.
Strong mid-level subsidence and deep southerly flow will
contribute to an extended period of temperatures well above
climo. While there is high confidence in a warm and mostly dry
period, there area a few times within the forecast with much
lower confidence. The first concerns a backdoor cold front Thu
night into Fri. Previous solutions had this feature moving into
the area late Thu night and lingering for much of Fri before
returning north as a warm front. However, recent guidance has
shifted away from this scenario, the both the GFS and ECMWF
being quicker to move the 1040 high across the Great Lakes and
into the Northeast. Given the propensity for ridging to hold on
longer than the guidance expects, am leaning in favor of a
warmer, drier solution Thu night and Fri. Another area of
uncertainty concerns potential cold front late in the period.
GFS/ECMWF currently bring this feature into the area later Sun,
but not confident it will arrive that early, which would
contribute to warmer temps Sun night.

Temperatures, as previously mentioned, will be significantly
above normal for much if not all of the period. Medium range
guidance continues to depict heights at levels not seen before
during the last week of Feb. At the same time 850 temps will
flirt with 15C. Away from the coast highs will run in the upper
70s to lower 80s through the period with the possible exception
of Fri. Closer to the coast, the combination of water temps in
the mid 50s and an onshore flow will keep highs much cooler.
The large temperature gradient will also create rather windy
conditions on the cool side of what should be a strong sea
breeze. Lows will range from the upper 50s to mid 60s through
the period. Average daily temperatures could run 20-25 degrees
above normal each day. Another way of putting it would be that
the departure from normal next week will be equal to what the
area experienced during the first week of January 2018, just in
the opposite direction.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 18Z...Time height shows solid low level moisture up
through 850 mbs for most of the day. IFR conditions will linger
inland this afternoon, but should briefly break before returning
this evening. Winds will be predominately southerly this
afternoon, with a stray shower possible. Tonight, there is a
solid chance for LIFR conditions, probably after midnight,
associated with the warm air advection. Tuesday, fog/stratus
will dissipate by mid morning with a continued southerly wind.

Extended Outlook...VFR with periods of MVFR through Fri. Good
chance of extended periods of IFR/LIFR in sea fog coastal
terminals Tues-Fri.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 945 AM Monday...The warm front should begin the enter the
coastal waters shortly, shifting northeasterly winds around the
south but with only a modest increase in wind speeds. The bigger
issue may come as the moisture content of the atmosphere jumps
up behind the front. Nearshore water temperatures in the 53-55
degree range may be cold enough to trigger the development of
sea fog beginning this afternoon and lasting perhaps into
Tuesday. We`ll continue to monitor this potential and may need
to issue a marine Dense Fog Advisory sometime later today. Seas
of 2-4 feet should decrease by 0.5 to 1.0 foot through tonight.
Discussion from 300 AM follows...

A coastal trough/warm front aligned just off the Carolina coast
will push inland and north through today. Therefore NE winds
will shift around through today to the E-SE and eventually S by
late this aftn into early this evening. This will leave a warm
and moist southerly flow as Bermuda High pressure begins to
dominate through tonight. Winds around 10 to 15 kts early this
morning will basically fall and remain around 10 kts or less
through the period with seas falling to 2 to 3 ft by this
afternoon. The only hazard may be the development of sea fog. As
dewpoint temps rise into the lower 60s through today into
tonight and cool shelf waters remain in teh mid 50s, the
potential will exist for some sea fog. SREF probs for vsby less
than 1 mile are close to 80 percent off of the SC coast and
spread northward in southerly flow.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM Monday...Western Atlantic Ridge will bring benign
winds and seas. The wind will be S at 10 kt or less, although
afternoon and early eve winds should be in the 10 to 15 kt range
near shore due to the seabreeze circulation. Seas will be 2 to 3
ft although some 4 ft seas should begin to mix in Wed night.

The risk for some sea fog will remain through the period. Sea
surface temps across the near shore waters are in the mid 50s
while dewpoints advecting across these waters will be in the
lower to mid 60s, so just marginally conducive for sea fog
development. Also, the expected wind direction is not particularly
favorable for increasing the residence time over the cool shelf
waters. At this time, have only included patchy sea fog through
the entire forecast period.

LONG TERM /THURSDAY THROUGH FRIDAY/...
As of 300 PM Sunday...Bermuda High will extend across the
waters through the period, maintaining south to southwest flow
with speeds 10 kt or less. Weak backdoor cold front will try to
drop in from the north early Fri, but it is starting to look
like the front will stall before reaching the area. Flow may
become a little more easterly during Fri, depending where the
front ends up, but speeds would drop closer to 5 kt. Seas will
run 2 to 3 ft through the period with occasional 4 ft possible
near Frying Pan Shoals later Thu and Thu night.

&&

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

&&

$$

SYNOPSIS...RGZ
NEAR TERM...TRA/RGZ
SHORT TERM...RJD
LONG TERM...III
AVIATION...DL



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