Area Forecast Discussion
Issued by NWS Wilmington, NC
FXUS62 KILM 211929
Area Forecast Discussion
National Weather Service Wilmington NC
329 PM EDT SAT MAY 21 2016
Showers and thunderstorms are possible ahead of a cold front
today. An upper low will keep conditions cool with a slight
chance for showers through Monday. More summer like weather
develops by the middle of next week with above normal temperatures
and drier conditions continuing into next weekend.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 300 PM Saturday...The mid-level s/w trof mainly responsible
for the rain this morning, has accelerated well ne of the area. In
its wake, weak subsidence aloft will partially keep a lid on
convection this afternoon. Daytime insolation has broken thru to
the sfc...and now the stratus deck has transitioned into a cu
field across the Carolinas. This will lead to increasing sfc based
instability with Nambufr Soundings indicating 2000+ CAPE by late
this aftn and into the early evening, along with DCape values
increasing to 800+. SFC forcing from a cold front dropping
southward will provide the necessary forcing to help initiate
convection. The time frame for this to occur will be from late
this afternoon thru the mid evening hours with 30-40 pops covering
it. Looking over the various thunderstorm parameters, the best
potential from these storms will be strong wind gusts. Have
highlighted the hazardous weather outlook to convey this
Afternoon highs should break into the 80s across the majority of the
ILM CWA. Even along the immediate coast where westerly winds aloft
will be strong enough to keep the sea breeze pinned if its able to
develop. Tonights lows will depend on how much caa occurs after the
cfp. Leaned toward the higher end of the available min temp mos
.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 /19Z SATURDAY THROUGH THURSDAY/...
As of 18Z...All shwrs/tstms moved off this coast this morning
leaving a fairly solid field of stratus which has broken up into
stratocu around 2k-4k ft. Expect cu field to break up further this
aftn, but increased sunshine will lead to increased instability
and therefore potential for tstms later this aftn into this eve
ahead of an approaching cold front.
After midnight expect some MVFR fog with potential for stratus
heading into Sunday morning as winds shift from W-NW to N as cold
front comes through.
Extended Outlook...Possible MVFR conditions on Monday, otherwise VFR.
NEAR TERM /THROUGH TONIGHT/...
As of 300 PM Saturday...The earlier band of pcpn has pushed well
ne of the area by early this aftn. This will leave only isolated
convection at best for this aftn. Expect convection to move off
the mainland thruout the evening hrs in response to a cold front,
currently draped ne to sw across northern nc, dropping southward
tonight. Isolated tstorm wind gusts could reach 30 kt. the cfp
will occur from n to s...and should be thru thru the ilm NC and
SC waters by daybreak Sun.
the sfc pressure pattern this aftn and evening will yield mainly
westerly winds, becoming nw-n later this evening and overnight
after the cfp. The sfc pg will remain relatively weak with 10 to 15
kt wind speeds thru the period.
Significant seas will run 2 to 4 ft...with dominating 6 to 8 second
periods. The 4 footers will primarily occur across the ILM NC waters
from Cape Fear northward.
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 kts 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.