Area Forecast Discussion
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FXUS62 KILM 210014
Area Forecast Discussion
National Weather Service Wilmington NC
814 PM EDT Mon Mar 20 2017
Mild weather will precede a cold front that moves through during
the predawn hours of Wednesday. A late week cooldown will be
followed by a weekend warmup and slow rise in rain chances.
.NEAR TERM /THROUGH TUESDAY/...
As of 300 PM Monday...Fair conditions to prevail into the
evening with a thin arrival of high altitude ice clouds
overhead, and perhaps a few mid-level clouds into the predawn
hours as increasing moisture arrives on W-NW trajectories. The
team-play of weak return southerly flow and thin clouds aloft
should help to keep temperature considerably milder than last
night, mainly middle and upper 40s.
Big diurnal temperature range on tap for Tuesday as 40s leap
into the middle 70s to lower 80s by afternoon ahead of an
approaching cold front. The large land versus ocean temperature
differential will drive a robust sea breeze circulation,
spreading cool air into the coastal interior, while producing
hearty afternoon wind gusts of 25 mph or so along and near the
coast. Dewpoints in the upper 50s to around 60 and good heating
inland, will lead to a chance of TSTMS over the interior by
late afternoon as 850-700 mb moisture become richer. Approaching
short-wave will increase bulk-shear parameters but mainly after
sunset. A few strong TSTMS NW of the area may begin to approach
the I-95 corridor late in the day, which by then could already
have a history of hail and strong wind gusts.
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...A cold front comes through Tuesday night
though forecast soundings show that it only has a depth of about
1200 ft. This will not be very conducive of the higher QPF seen in
the GFS but likely the much more paltry amounts depicted by the WRF.
The former is also stronger with a mid level shortwave, and should
this come to pass then rainfall amounts may be a tad higher. Current
forecast will thus be in between the two models and show up to a
tenth of an inch inland. Getting the low temp forecast correct is
tricky and depends highly on the timing of the boundary. Most of the
night will be exceedingly mild but there could be quite a drop in
temps towards daybreak. The depth of the inversion increases to 4kft
Wednesday afternoon but an overall drying of the deep layer column
will likely mean measurable rainfall becomes hard to come by. The
low amplitude mid level flow and highly sloped front will help to
slightly temper the cold advection Wednesday afternoon. Though much
cooler than Tuesday afternoon temperatures will still be only about
a category below climatology. The upper trough off the East Coast
slightly sharpens Wednesday night turning a deeper layer locally to
the north. Nighttime lows will not vary as much N to S as previously
thought with southern zones staying in the low 40s while far
northern zones may dip into the mid 30s. A light freeze may be
possible over the cool spots in Pender County.
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 AM Monday...Canadian high pressure over the eastern
Great Lakes Thursday morning will move off the Mid-Atlantic
coast Thursday night and farther offshore Friday. After a chilly
day Thursday with highs only in the 50s we could see one last
night of frost or freeze conditions Thursday night with light
winds in the vicinity of the high. By Friday return flow around
the high should begin to modify the airmass with highs returning
to the 70s by Saturday.
The next synoptic frontal system should begin to move across the
Southeast states this weekend, perhaps spreading showers and
t-storms into the Carolinas Saturday, but with better chances
by Sunday. SPC, in their extended range convective outlook,
mentions weak instability across the warm sector including the
Carolinas but with too much uncertainty to consider a severe
weather risk for now.
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 00Z...VFR conditions expected thruout the 24 hr TAF
Issuance Period. High pressure`s center will become elongated
and stretch from the Gulf of Mexico across Florida to off it`s
east coast. Weak sfc warm front will push north of the area this
evening. A low level southwesterly jet will develop overhead
late this evening and persist into daylight Tue. A sfc cold
front dropping southward during Tue will be on the northern
doorsteps of the ILM CWA by the end of this period. Will see 25k
ft ceilings thru out this period, occasionally a 10k to 15k foot
ceilings later tonight thru much of Tue. And possibly a Cu or
SC scattered deck at 4.5k to 6k ft at the end of this period.
Pcpn chances too low to include at the end of this period.
Extended outlook...VFR expected through the period except for
possible MVFR/IFR conditions from ceilings and convection
associated with the cold frontal passage Tuesday night into
NEAR TERM /THROUGH TUESDAY/...
As of 300 PM Monday...Nice marine conditions this afternoon to
early evening, will begin to deteriorate a bit as SW winds
increase tonight, and remain elevated through Tuesday ahead of a
cold front. Right now it doesn`t appear an Advisory will be
needed but an Exercise Caution statement cannot be ruled out
entirely on Tuesday as seas approach 5 feet offshore with gusts
to 20 KT. The wave spectrum will be built by moderate to heavy
S-SW chop Tuesday with 1-2 foot E waves every 10-11 seconds.
No TSTMS expected until Tuesday night. The period from this
afternoon into evening will see the E swell as the dominant
wave energy until winds increase late.
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 300 PM
Monday...Tuesday afternoon`s agitated pre-frontal wind field will
actually relax slightly Tuesday night as a cold front pushes into
the area thanks to a pressure trough along the boundary. Any
response in seas may be too gradual to be very noticeable. What will
be much more noticeable is the post-frontal wind and wave regime
that sets up by Wednesday. Flow will veer markedly to the NE and
increase. A small craft advisory will be needed Wednesday and
Wednesday night in the pinched gradient.
LONG TERM /THURSDAY THROUGH FRIDAY/...
As of 300 AM Monday...Canadian high pressure over the Great
Lakes on Thursday will sink southeastward to the Virginia coast
Thursday night, then will move offshore Friday. Clockwise winds
blowing around the high will probably maintain Small Craft
Advisory conditions for most of Thursday, if not Thursday night.
By Friday a weaker pressure gradient on the west side of the
high should allow veering winds to diminish to less than 15
knots. A significant east to northeast backswell is expected to
continue through Friday due to the large area of strong winds
covering the western and central Atlantic around the periphery
of this high.