Scientific Forecaster Discussion
fxus62 kilm 251037
Area forecast discussion
National Weather Service Wilmington NC
637 am EDT Mon Sep 25 2017
Hurricane Maria is expected to remain offshore and move slowly
north, with its center passing about 250 miles east of Cape
Fear Tuesday night. Dangerous beach and marine conditions will
prevail much of the week. A cold front should reach the area
late Friday, bringing cooler and drier air into next weekend.
Near term /through tonight/...
as of 327 am Monday...ridging aloft over the mid-Atlantic and
5h low/trough over the eastern Gulf Coast will gradually weaken
today as Hurricane Maria moves slowly northward. Maria will pass
well east of the area later today and tonight. The pinched
gradient between the surface high nosing down the coast and
Maria is likely to create breezy conditions this afternoon and
evening, especially along the NC coast. Although there will much
deeper moisture compared to the last few days, precip chances
are not any higher. Maria will be spreading moisture below 500mb
over the region but the subsidence on the periphery of the
storm will keep the atmosphere capped. Despite precipitable
water values approaching 1.9 inches it appears measurable precip
will be hard to come by. Scaled back pop a bit for today,
taking out any mention of showers into the evening. Did hold
onto slight chance pop for the NC coastal counties overnight as
Maria moves ever so closer. Do not have a lot of confidence in
this but there will be an abundance of low level moisture and a
bit of convergence right along the coast. High temperatures will
trend a little cooler today compared to sun with low to mid 80s
expected. Lows will likely trend slightly warmer due to
increased boundary layer winds and moisture/cloud cover, ranging
from mid 60s to around 70.
Short term /Tuesday through Wednesday night/...
as of 327 am Monday...this period will witness a slow migration
north of Maria, forecast to be a category 1 as it passes 250
nm east of Cape Fear late Tuesday night. Primary hazards are
powerful surf and large breaking waves due to the speed of the
long-period sets. As a result the 'high surf advisory' will
likely remain posted at least through Tuesday, laced with lethal
rip currents and clipping, swift beach run-up. A few outer
bands may be flung ashore Tuesday but no severe threats
anticipated, in fact moisture remains shallow to the extent only
showers are advertised. Peak low-level winds appear timed for
Tuesday and any landward moving rain bands could throw a 30-35
mph gust at the coast, favored mainly from Cape Fear northward
where greater easterly longitude in intrinsic there. Maximum
temperatures both Tue/Wed mid 80s. Winds and a few clouds may
hold mint values up at around 70s both Wed/Thu morning.
Long term /Thursday through Sunday/...
as of 3 PM Sunday...Maria, forecast to be well to the east-
northeast of the area at the onset of the period, will continue
moving north and east away from the area. A cold front will drop
into the area Thursday night and move out to sea Friday,
ushering in cooler and drier air for the weekend.
Outside of a small chance of showers Wednesday, mainly over
northeast sections of the forecast area, the extended range
looks mainly dry. High temperatures in the mid 80s to around 90
Wednesday and Thursday will cool to the mid 70s by Sunday. Min
temperatures in the upper 60s to lower 70s will cool to the
upper 50s to lower 60s by Saturday night.
Aviation /12z Monday through Friday/...
as of 1045z...while VFR conditions will be dominant during the
period there will be a period of IFR/MVFR morning near and along
the coast. Onshore flow well ahead of Hurricane Maria will
increase low level moisture which guidance suggests will
manifest as a broken/overcast deck between 2k and 3k ft. Looks like only
the coastal sites will see this MVFR stratus ceiling. Winds
will remain from the northeast through the period with speeds
8-12 kt, but along the coast gusts could exceed 25 kt later
today. MVFR ceilings will again be possible at the coastal
Extended outlook...MVFR ceilings may develop at the coastal
terminals as stratus advects onshore Tue. Wind speeds at the
coastal terminals will gust as high as 15 to 25 kt through Wed.
near term /through tonight/...
as of 327 am Monday...although Hurricane Maria remains well to
the southeast, the gradient between the storm and high pressure
to the north will maintain northeast winds today, becoming north
winds overnight. Speeds will stay in the 20 to 25 kt range
through the period and gusts will have the potential to exceed
30 kt. Seas, mostly made up of swell from Maria, will range from
5 ft near shore to as high as 11 ft across outer edges of the
Short term /Tuesday through Wednesday night/...
as of 327 am Monday...sea heights will peak Tuesday as Maria
moves slowly north about 250 miles offshore of Cape Fear, with
7-14 foot high waves on tap, highest offshore, and lowest
inshore along SC where sea bottom friction will consume a chunk
of the swell energy. Inlet turbulence may be expected during
outgoing tides much of this week. Large breaking waves will pose
a threat near sand bars, and the surfzone will extend much
farther than usual due to the large and long period waves. Winds
will peak Tuesday north 20-30 kt, and well offshore a few gusts to
35 knots will probably occur, although confidence is not high for
full gale conditions to be expected at this time. At a minimum,
Small Craft Advisory cond are expected through this entire period.
Long term /Wednesday through Friday/...
as of 3 PM Sunday...northwest winds of 15 to 25 knots Wednesday
morning will diminish to 10 to 15 knots by Thursday morning. A
shift to the north then northeast will occur Friday and Friday
night. Seas of 4 to 7 feet south and 7 to 9 feet north will subside
through the period, falling to 3 to 4 feet by Friday.
SC...high rip current risk through Tuesday evening for scz054-056.
High surf advisory until 9 PM EDT Tuesday for scz054-056.
NC...high rip current risk through Tuesday evening for ncz106-108-
High surf advisory until 9 PM EDT Tuesday for ncz106-108-110.
Marine...Small Craft Advisory until 6 PM EDT Wednesday for amz250-252-