Area Forecast Discussion
Issued by NWS Wilmington, NC

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000
FXUS62 KILM 240738
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
338 AM EDT WED AUG 24 2016

.SYNOPSIS...
High pressure at the surface and aloft will affect the Bi-State
region of North and South Carolina through the end of this week,
and likely continuing thru the upcoming Weekend. This will result
in a POP-less forecast thru Friday, with only isolated showers or
thunderstorms possible this upcoming weekend. Basically looking
at partly to mostly sunny days and mostly clear to partly cloudy
nights thru this weekend. Temperatures will run near the normals
for this time of the year.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Wednesday...A 700-500 mb ridge centered along the
Gulf Coast will maintain a strong convective cap across the
Carolinas today. The subsidence inversion on yesterday evening`s
00z Greensboro, NC sounding was impressive with air temperatures
going from +8C at 7300 feet AGL to +12C at 7900 feet AGL. Dry
weather is forecast again today as east-northeasterly low-level
winds continue around surface high pressure centered off the NJ
coast. Only some flat high-based cumulus clouds are expected today
at the base of that subsidence inversion. 850 mb temps should
range from +14C to +15C this afternoon, sufficient in this dry
airmass for highs in the upper 80s to around 90.

The high off the Mid-Atlantic coast should weaken, but a ridge
axis will continue to extend southwestward across Virginia and
into western North Carolina. Since we`re south of this ridge a
light northeast wind should continue. Lows should fall into the
mid to upper 60s with some lower 70s on the beaches.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 AM Wednesday...The 700-500 mb ridge will build eastward
Thursday and should be centered over North Carolina on Friday. This
will maintain warm and very dry mid and upper level conditions. The
low-level airmass will modify a little each day as the tropical
ocean water in the western Atlantic feeds heat and moisture into
the boundary layer. This should lead to rising temperatures and
dewpoints for us as this modified air advects onshore. It`s not
impossible that the early morning landbreeze could pop off some
shallow convection over the coastal waters Thursday and/or Friday,
with the low-level easterly flow perhaps pushing one or two of
those ashore.

Forecast highs in the 90s will expand Thursday and particularly on
Friday due to the warming airmass. Dewpoints rising back toward 70
should add a stickiness we`ve become quite used to this summer, and
heat indices Friday afternoon could be in the 94-98 degree range.
Overnight lows mainly in the upper 60s Thursday night and lower 70s
Friday night.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...At the start of this period the 2 long-term
global models, GFS and European, both indicate an Upper High
centered overhead, across the NC and SC region. This position
basically holds thru Sunday. At the sfc, a weak ridge axis will
extend across the region from the ene. This ridging extends from
the center of high pressure that was once a 1025+ mb high located
just off the NE States today. Mos Guidance indicates Sat will be
the warmer day of the 2 days this weekend, with most places seeing
90+ except the immediate coast where onshore flow persists. On
Sunday, a weak to modest ne surge occurs. This a result of weak
ridging on Sat giving way to ridging from another 1025+ mb high
that moves once again across the NE States. Could see isolated
convection along the resultant wind boundary Sun but ridging aloft
will prevent any further or deeper convection to occur. Highs
Sunday will be a degree or 2 lower than Sat highs.

For Monday and Tuesday time frame, the 2 global models have their
particular solutions for the upper high and associated ridging to
maneuver across the Southeast States with its relative positioning
to become quite important with respect to the potential for a
Tropical Cyclone threat either on the East Coast of the U.S. or
the Gulf Coast. For now, Monday and Tuesday will see a decent
onshore flow especially in the low levels. If it becomes deep
enough, showers may move onshore late at night...followed by low
chance for diurnally driven low topped convection over land each
day. Will keep POPs at 30 percent or lower this period due to the
uncertainty. Temps will run at or a couple degrees below the norm.

Wavewatch3 and locally run SWAN models, both respectively indicate
the leader swells from Gaston located over the High Seas of the
Atlantic at this time period, will begin affecting the local
beaches by Midday Sunday. This will result in Moderate to Strong
Rip Currents on Sunday across all beaches. Will advertise
this in the hazardous weather outlook.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
As of 06Z...Could see scattered stratocu or altocu at the 5k to
7k foot range early this morning as seen with the latest ir 11-3.9
micron channel.

Otherwise, even drier air will continue to infiltrate the Bi-
State region from the northeast complements of a 1025+ mb high
poised to move off the New England Coast later today. Still enough
low level moisture below 850mb to aid in the diurnally driven cu
especially along the resultant wind boundary. With subsidence
aloft, the vertical extent of the cu will be shunted and therefore
do not expect any convection to occur. The diurnally driven cu
will dissipate quickly by/after sunset. The sfc pressure pattern
and gradient will yield 030-060 wind directions at 4 kt or less
prior to sunrise, increasing to 5 to 10 kt by midday. The coastal
terminals will see a resultant wind boundary set up by early
afternoon and make some progress inland. Coastal terminals will
see winds veer to 070-100 degrees at 10-12 kt during the aftn and
early evening then back to 040-070 at 4 to 6 kt after sunset.

Extended Outlook...VFR CONDITIONS THRU THE PERIOD EXCEPT FOR
POSSIBLE BRIEF MVFR CONDITIONS FROM ISOLATED CONVECTION SUN.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 300 AM Wednesday...Surface high pressure is centered a couple
hundred miles off the New Jersey coast. The high will move slowly
eastward today and tonight, but a ridge axis will continue to extend
southwestward across Virginia and into western North Carolina.
Surface pressures across the northern Bahamas and Florida are fairly
low, and this difference in pressure will maintain an east-
northeasterly wind across the Carolina coastal waters. Wind speeds
of 15-20 kt early this morning should diminish to 10-15 kt this
afternoon.

Seas have been churned up by the wind over the past 6-8 hours and
buoy reports at 2 AM include 4.1 feet 5 miles SE of Wrightsville
Beach and 4.6 feet at Frying Pan Shoals. These areas of 4+ foot seas
should die away by noon with 2-3 foot seas anticipated for the
afternoon into tonight.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 300 AM Wednesday...High pressure along 40 degrees latitude
will continue to weaken Thursday and Friday even as a ridge axis
extends southwestward across Virginia and western North Carolina.
As the pressure gradient decays between the weakening high and
lower pressures present across the Bahamas and Florence, wind
speeds should diminish to around 10 knots by Thursday night into
Friday.

Winds this light would normally equate to 2 foot seas, however
we`ll begin to pick up a long period east-southeast swell from at
least one and perhaps two tropical systems in the Atlantic. This
should create combined sea heights of 3 feet to locally 4 feet by
Friday.

LONG TERM /SATURDAY THROUGH SUNDAY/...
As of 300 AM Wednesday...Weak Sfc ridging from the ene on
Saturday will produce a 10 to 15 kt ene wind across the area
waters. Wind driven waves or even a pseudo ground swell will
dominate the significant seas with 3 to 4 ft common with a few 5
footers possible, with periods in the 6 to 8 second period range.
For Sunday, the sfc ridging re-positions to a "new" center of high
pressure moving across the NE States. The sfc pg does increase,
resulting in NE winds at a solid 15 kt possibly up to 20 kt. The
2 to 4 foot pseudo ground swell at 6 to 8 second periods, will
become mixed with the easterly leader swells from Gaston running
at 13 to 16 second periods.

Wavewatch3 and locally run SWAN models, both respectively
indicate the leader swells from Gaston, located over the High
Seas of the Atlantic at this time period, will begin affecting
the local waters by midday Sunday and continuing there-after. The
combined pseudo ground swell and leader swells from Gaston, could
reach SCA thresholds during the aftn and night. Will advertise
this in the hazardous weather outlook.

&&

.CLIMATE...
As of 300 AM Wednesday...Shortly before 2 AM this morning
Wilmington`s official temperature here at the airport touched 69
degrees. This ends the streak of consecutive days with low temps 70
degrees or warmer at 58, now the all-time longest streak in
Wilmington history dating back to 1874.

Wilmington`s Consecutive Days with Low Temperatures 70+ degrees
#1  58 days 6/27/2016 to 8/23/2016
#2  56 days 6/29/2012 to 8/23/2012
#3  52 days 6/22/1941 to 8/12/1941
#4  48 days 7/ 6/1986 to 8/22/1986
#5  46 days 6/28/1991 to 8/12/1991

Yesterday morning the streak of consecutive 70+ low temps in
Florence was broken at 62 days. This is also an all-time record for
Florence dating back to 1948.

Florence`s Consecutive Days with Low Temperatures 70+ degrees
#1  62 days 6/22/2016 to 8/22/2016
#2  60 days 6/26/2005 to 8/24/2005
#3  55 days 7/ 6/1975 to 8/29/1975
#4  46 days 7/10/2010 to 8/24/2010
#5  45 days 6/11/2015 to 7/25/2012
#5  45 days 6/28/1991 to 8/11/1991

From a climate perspective, the summer of 2016 has been interesting
in that daily highs and lows have been among the warmest average
readings in history without having any individually extremely hot
days. In Wilmington since June 1st our average high temperature is
the fifth hottest in history and average low temperature is the
third hottest, but the highest temperature this summer of only 98
degrees was not exceptional at all. Florence since June 1st has had
its seventh hottest average daily high temp, record hottest daily
low temp, but the highest temperature of the summer at 98 degrees is
actually cooler than the "normal" hottest annual temp of 101.

&&

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

&&

$$
SYNOPSIS...DCH
NEAR TERM...TRA
SHORT TERM...TRA
LONG TERM...DCH
AVIATION...DCH
CLIMATE...tra



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