Area Forecast Discussion
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FXUS62 KILM 212345
Area Forecast Discussion
National Weather Service Wilmington NC
745 PM EDT SAT MAY 21 2016
Showers and thunderstorms will move across portions of the area
tonight ahead of a cold front which will move offshore late. An
area of low pressure aloft will bring a slight chance of showers
Sunday and Monday. Summer-like temperatures and mainly dry
weather will develop by the middle of next week with above normal
temperatures into next weekend.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 700 PM Saturday...mid-level shortwave energy will approach
the Carolinas tonight with one spoke of this energy moving through
on Sunday. A surface front is coincident with this shortwave. A
line of showers and thunderstorms was moving across the central
Carolinas early this eve. Consensus amongst the high resolution
models continue to support the best coverage of showers and
thunderstorms moving across the I-95 corridor 00-03z and then the
remainder of the area...moving offshore around 06-07z. However...
there is some discrepancy as to how much convection will actually
reach the more immediate coastal areas as with time...the
environment will continue to slowly stabilize. At this time...
have decided to include pops in the 40 percent range for most of
the area...lower as you move south across the southern Grand
Strand and South Santee River areas...furthest removed from the
best upper level support.
A few of the upstream storms have been strong to severe...
although a slow weakening trend is expected with the loss of
heating through the evening. Will mention an isolated strong
thunderstorm in the HWO into late this evening.
A cold front should be moving off the coast late tonight. Light
winds and only slowly lowering dewpoints toward morning may result
in patchy to areas of significant late night fog...especially in
locations where heavy downpours occur later this eve.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...The start of this period will feature the
upper trof extending down the east coast Sunday morning. The upper
trof closes off and nearly becomes a cutoff low depending on your
definition. The upper low`s center over the VAs Sunday afternoon is
progged to drop southward to a position over eastern NC by daybreak
Mon. And remarkably, the models are in pretty good agreement in
lifting this closed low northward to basically off the NJ Coast by
Like spokes on a bicycle wheel, there will be mid level s/w trofs or
vorts rotating around this upper low. With decent or o.k. lapse
rates, available moisture, and if enough daytime insolation to
further aid instability, convective chances should increase ahead
and in the vicinity of these rotating s/w trofs. Models are at times
different with the timing of their movement across the fa, but
nevertheless the threat for convection will exist especially during
each day. At night, depending on the strength of the upper s/w trof
rotating thru, will likely have to carry low pop convection well
into Sun night. In addition...model sounding data indicate 500mb
temps drop to -19 degrees C and as a result, small hail from any of
the convection will become a possibility.
The end result is that this cold core upper low affecting the area
Sun thru Mon night means temperatures will average 5 to 10 degrees
below normal this period. Normal daytime highs run in the low to mid
80s and night time lows in the lower 60s.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 300 PM Saturday...Warm summertime weather forecast for the
upcoming week as a pattern more typical for this time of year
finally sets up. Upper level low will be migrating off to the
northeast on Tuesday as ridging blossoms northward from the Gulf of
Mexico. As this happens...surface high pressure will re-center
itself off the southeast coast...with a Bermuda High type setup
forecast for the remainder of the period. The combination of warm
return flow around the surface high and bulging heights beneath the
mid-level ridge will create warm and mostly dry conditions as
subsidence prevents much in the way of even diurnal convection. The
exception still looks like Thursday when a weak impulse will rotate
atop the ridge and cause subtle height falls...which when combined
with the increasingly unstable airmass as heat and humidity
increase...should fire off some storms Thursday/Thursday night.
Otherwise...the extended looks very nice with highs and lows
slightly above climo under ample sunshine.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 00Z...The main question for this TAF issuance is whether
upstream convection will hold together to affect area terminals
tonight. At this time...it looks most probable for showers and
storms to affect northern and western terminals in the 01Z to 05Z
window. Southern terminals should remain unscathed.
Otherwise...VFR conditions are expected tonight until MVFR fog
develops after midnight. Fog should burn off by 14Z with VFR
conditions expected for the remainder of the TAF period with
isolated to scattered afternoon thunderstorms possible. Light winds
tonight will become NW at 5 to 10 KT after daybreak Sunday.
Extended Outlook...Possible MVFR conditions on Monday, otherwise VFR.
NEAR TERM /THROUGH TONIGHT/...
As of 700 PM Saturday...A cold front will move across the waters
early Sunday morning. A wave of low pressure on this front may
slow the push offshore. The wind direction will remain from the SW
at 10 to 15 kt through late eve...then shift to the W and NW well
after midnight. Wind speeds will decrease to 10 kt or less
overnight before bumping higher Sun morning. Seas will be mainly 2
to 3 ft. Isolated to scattered showers and thunderstorms are
expected to move across the waters late tonight.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 PM Saturday...The sfc cold front will slowly drop south of
the area waters early Sunday morning. Winds behind the cfp, will
veer to the NW and NNW Sunday and persist in this direction thru
Monday. For Monday Night, with the upper low now lifting to the
north, away from the area waters, the sfc pressure pattern will
become less dominated by the cyclonic flow associated with this
upper low. This will result in winds slightly backing to a westerly
direction. The sfc pg thru Monday will remain weak across the ILM SC
waters, and 1 step hier than weak across the ILM NC Waters. This
will yield wind speeds in basically the 10 to 15 kt range...with the
hier side of this range across the ILM NC Waters.
Significant seas will range between 2 and 4 feet thru the period,
with the 4 footers occurring primarily early in the period,
basically thru early Monday and mainly across the ILM NC Waters.
Dominating periods will basically range between 7 and 9 seconds.
With an offshore wind, wind driven waves will be minimal due to the
limited fetch. As a result, an ese 1 to 3 foot ground swell will
become the primary significant seas producer, hence the hier
Upper s/w trofs rotating around the upper low will sporadically move
across the area waters thruout this period. Dynamics from these will
be enough for convection to also sporadically occur.
LONG TERM /TUESDAY THROUGH THURSDAY/...
As of 300 PM Saturday...Westerly winds Tuesday will transition to
the S/SW Wednesday and then remain from that direction for several
days as high pressure offshore becomes the dominant feature. The
gradient in the vicinity of this high will be weak...so wind
speeds will be around 10 kt each day regardless of direction.
Although a SE 8-9 sec swell will amplify within the
spectrum...especially late in the period...wave heights will
remain just around 2 ft Tue/Wed...rising to 2-3 ft late thanks to
that growing aforementioned swell.