Area Forecast Discussion
Issued by NWS Wilmington, NC

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749
FXUS62 KILM 280019
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
719 PM EST Mon Feb 27 2017

.SYNOPSIS...
A warm front will lift north tonight leading to isolated showers
but near record high temperatures Tuesday and Wednesday. A
strong cold front will bring thunderstorms Wednesday night into
Thursday morning, followed by seasonable temperatures late week.
Even cooler temperatures are expected by the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 300 PM Monday...Warm air advection will commence in force
later tonight as high pressure offshore moves into a more
favorable position for southerly winds. Guidance continues to
show mixed signals with regards to pops for tonight and Tuesday
with the NAM being by far the more agressive solution. Overall I
leaned with the drier GFS but a few scattered showers can`t be
ruled out. By Tuesday afternoon the GFS shows a sea breeze
convective scenario so I did show a subtle increase in pops at
this time. Temperatures are lagging a little behind this
afternoon with a few more clouds than anticipated and shouldn`t
drop off too much overnight with the return flow taking shape.
Expect another warm one for Tuesday with highs generally in the
middle 70s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...Active period through mid-week as near
record highs give way to a strong cold front and widespread
convection Wednesday night.

Period begins Tuesday night with high pressure offshore and a warm
front well north of the area. Increasing SW winds will drive strong
WAA Tuesday night, and mins will likely fall only into the low 60s,
mid 60s at the coast. This is more representative of early March
highs, and sets the stage for what will be a very warm day on
Wednesday. Drying in the mid-levels behind Tuesday`s front will
allow sunshine to break through the mid/high level cloudiness which
will combine with 850mb temps of 12-14C - near all-time highs for
the date according to SPC Sounding Climatology. This suggests highs
approaching records Wednesday aftn, with widespread 80+ away from
the immediate coast.

Forecast for Wednesday, March 1:
Wilmington, NC:     81   Record: 83 (1918)
Florence, SC:       84   Record: 84 (1997, 1951)
N Myrtle Beach, SC: 77   Record: 81 (1955)

Wednesday will be very warm, and with deep SW flow, instability
will increase as dewpoint values rise into the 60s. This will
set the stage for a possible severe weather event Wednesday
night as a cold front races across the region. The Storm
Prediction Center has our area in a MRGL risk for severe
Wednesday night. A strong cold front will be reaching across the
area driven by a potent vorticity impulse moving into New
England causing height falls locally. Since this front is
expected to cross overnight, likely after midnight, instability
will be waning, but an HSLC event is possible. While these
nocturnal events do not usually create widespread severe, over
50 kts of wind at 1500 ft AGL help to produce bulk shear values
over 50 kts, DCAPE of 400-700 J/kg, and 0-1km SRH of 200-300
m2/s2 creates looping hodographs. Additionally, SHERB values
reach 0.7 to 0.9 across far NW portions of the CWA, with lower
values elsewhere. This supports at least an isolated damaging
wind threat even overnight, as well as an isolated tornado
threat, but widespread severe is not forecast. However, a
weakening squall line will likely move across the area and most
places will receive a gusty shower with briefly heavy rainfall.
The highest threat for any severe will be west of I-95 Wednesday
night.

Temps will crash behind the front, but because of the late FROPA,
mins will only have time to fall into the mid 50s well inland,
around 60 at the coast, still well above normal for the date.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 230 AM Monday...Cold front will be off the coast as the
period begins with strong cold advection underway. Showers may
linger in the area for the first part of Thu morning, especially
along the coast but any activity would be short lived. Canadian
high builds in from the northwest Thu into Fri under broad 5h
trough aloft. Reinforcing shot of cold air arrives Fri
afternoon, along with an increase in northwest winds and a drop
in relative humidity. The center of the surface high settles
over the area Sat morning, sliding just off the coast into Sun.
Pattern aloft transitions from broad troughing to flat flow,
which helps push the surface high off the coast Sun.
Temperatures near climo Thu and Fri will dip below climo Fri
night and Sat. Temperatures will bounce back to climo Sat night
as the return flow develops on the backside of the high.
Increasing southerly flow Sun combined with westerly flow aloft
will push temps several degrees above climo as the period ends.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 00Z...VFR for much of the valid TAF period. However, there
is a risk of MVFR ceilings and visibility in showers, mainly
between 08z and 15z. A warm front will move across the terminals
late tonight and Tue morning.

Extended Outlook...VFR. However, there is a risk for reduced
ceilings and visibility in showers and thunderstorms, mainly Wed
night into Thu morning.

&&

.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 300 PM Monday...A lazy southeast to sometimes east to
northeast flow is currently in place across the waters. In time
winds will become more from the south as warm air advection
commences. Speeds will remain light on the lower end of a 10-15
knot range. Slightly more of a southerly component to the winds
Tuesday with similar speeds. Significant seas will overall show
a 2-4 foot range with four footers more prevalent Tuesday
afternoon and evening.

SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...Cold front will cross the waters late
Wednesday night, with SCA conditions possible. Ahead of this
boundary, SW winds will increase steadily from 10-15 kts early
Tuesday night, to 15-25 kts during Wednesday immediately ahead of
FROPA. The frontal passage will be accompanied by a sudden wind
shift to the NW with only slow decreasing speeds through the end of
the period. Seas of 4-7 ft are expected late Wednesday and Wednesday
night, rising from 3-4 ft Tuesday night, and a 5-6 sec southerly
wind chop will be the primary wave group. A subtle decrease in
amplitude is possible very late Wednesday night as the winds begin
to shift offshore.

Additionally, sea fog will be possible Tuesday night and especially
on Wednesday as high moisture air advects across cooler shelf
waters. Have not introduced any sea fog into the forecast attm as
there is some concern that Td-T spreads may be slightly too high,
and parcel residence times may not be long enough for saturation
due to the fast wind speeds. Will mention the possibility here
and address in the official forecast as we get closer to the
time of potential sea fog.

LONG TERM /THURSDAY THROUGH FRIDAY/...
As of 230 AM Monday...Strong cold front will be either moving
across the waters or just east of the waters as the period
begins. Offshore flow will drop from a solid 15 kt in the
morning to 10 to 15 kt in the afternoon. Weak offshore flow
continues Thu night into Fri before another surge of cold air
pushes across the waters Fri afternoon/evening. This surge will
push northwest flow to 15 to 20 kt with gusts approaching 25 kt.
Seas will trend down, from 3 to 6 ft Thu morning to 1 to 3 ft
Fri morning, as offshore flow decreases. Increasing winds later
Fri and Fri night will result in a slight bump in seas with
dominant wave becoming a short period wind wave.

&&

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

&&

$$

NEAR TERM...SHK
SHORT TERM...JDW
LONG TERM...III
AVIATION...RJD



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