Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 280159 CCA
AFDILM

Area Forecast Discussion...Corrected
National Weather Service Wilmington NC
958 PM EDT Thu Apr 27 2017

.SYNOPSIS...
High pressure offshore will bring a warming and drying trend
late this week through the weekend. A weakening cold front will
bring a few showers or a thunderstorm tonight inland and early
Friday at the coast. A stronger frontal system will bring a chance
of rain late Monday and early Tuesday. Another storm system may
impact the region with a soaking rain next Thursday.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 1000 PM Thursday...Low stratus is developing along the
South Carolina coast a few hours faster than anticipated. Have
increased sky cover forecasts and adjusted hourly temperature
curves appropriately as this is interfering with radiational
cooling. The line of showers across central and western South
Carolina is slower to move east than anticipated. Latest HRRR
runs show only spotty coverage as it enters the Pee Dee region
after midnight, but still shows a resurgence as it approaches
Cape Fear just before daybreak Friday. The HRRR is developing
surface-based CAPE near 3000 J/kg late tonight along the coast--
something I was going to immediately dismiss until I started
adjusting NAM soundings using the observed temp/dewpoint at Frying
Pan Shoals buoy (75/73) and easily got 2600 J/kg. Hmmmm... PoPs have
been bumped up to 30 percent in the Myrtle Beach/Cape Fear region
after 3 AM. Discussion from 730 PM follows...

Isolated showers and maybe even a thunderstorm will develop
overnight as a dying cold front approaches from the west. The
meager surface-based instability is becoming capped off due to
the cooling boundary layer, however elevated instability based
around 5000-7000 feet AGL will continue overnight. PoPs range
from 10-30 percent, lowest near Georgetown and highest west of
I-95. The last several HRRR runs and some of the recent RUC
model runs also suggest late- night showers could develop near
the Brunswick County coast, although I am not certain what
mechanism is in play.

No significant changes have been made to forecast low
temperatures, expected to range from the mid 60s near and west
of I-95 to the lower 70s on the beaches. This is exceptionally
warm for late April, about 15 degrees above normal.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM Thursday...Bermuda High will take hold of the area
with ridging all the way up through the mid and upper levels.
This will maintain a deep southerly return flow with very mild
summer-like weather. Plenty of dry air and subsidence through
the mid levels will maintain a cap on convection although
shallow low level moisture will be quite rich. Overnight winds
should prevent fog, but sounding data shows potential for a few
hours of saturated column up to 1500 ft or so and greater
potential Sat night into Sun morning. Therefore may see some
stratus around overnight but will dissipate as sun rises Sat
morning. Should also see some cu develop right along sea breeze
boundary as it pushes inland Sat aftn. Temps will run about 10
to 15 degrees above normal with plenty of sunshine on Sat. Both
Fri night and Sat night lows will near or around 70 degrees with
daytime highs soaring through the 80s to around 90 in many
spots inland.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 300 PM Thursday...Western Atlantic High Pressure will maintain
deep southerly flow on Sun. Although a shower along the seabreeze
can`t be ruled out, subsidence on the periphery of the ridge should
keep afternoon convection to a minimum, except along the inflection
point, will keep POPs out of the forecast at this time.

Surface and mid level ridge will weaken and drift east Mon, allowing
a cold front to approach from the W. Low pressure and associated
strong dynamics and upper level support will be well dislocated from
the Carolinas as a cold front moves across the area Mon night. This
suggests convection weakening as it moves into the eastern
Carolinas. Current timing brings the likelihood for showers and
thunderstorms later Mon and Mon night.

As the front moves off the coast Tue morning, high pressure along
the Gulf Coast will slide east and then offshore to our S during
Wed. This should bring a dry period. Deep low pressure will move out
of the mid south and Gulf coast states Wed, lifting slowly to the
NE. Its associated cold front will move into the Southeast states
Thu-Thu night, bringing the risk for robust thunderstorms.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 00Z Friday...Isolated convective showers associated with a
dying cold front may move into eastern North and South Carolina
later this evening. Odds of precipitation occurring at any of
the airports are 20 percent or less, and flight category
restrictions are unlikely. Perhaps of greater concern is the
potential that low stratus will develop late this evening as
very moist air gathering just offshore moves inland. Ceilings as
low as 600-800 feet are possible, with IFR restrictions forecast
in the TAFs for ILM, MYR, and CRE beginning around 05Z. It is
worth noting the NAM model has much greater potential for low
ceilings than the GFS or RUC models.

Any low ceilings will either burn off just after sunrise, or
push back offshore as wind directions veer more southwesterly
late tonight. VFR conditions are expected for all areas after
13-14Z Friday.

Extended outlook...VFR through Sunday. Periods of IFR/MVFR
conditions are possible in thunderstorms late Monday into early
Tuesday.

&&

.MARINE...
NEAR TERM /THROUGH FRIDAY/...
As of 730 PM Thursday...The afternoon seabreeze is beginning to
wind down as temperature contrasts across the beaches relax.
Wind gusts as high as 27 knots occurred at Wrightsville Beach,
24 knots at Topsail Beach, and 21 knots reported at the
Georgetown, SC airport. South-southwesterly winds 10-15 knots
are expected for the remainder of the night. Seas consist of
choppy 4-5 second wind waves overlaid with a 9 second southeast
swell, totaling 3-4 feet, and little change is anticipated
overnight.

SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM Thursday...Southerly return flow will persist
around the periphery of the Bermuda High which will keep a
stronghold on the local waters through the period. Winds will
run 10 to 15 kt with gusts to 20 to 25 kt possible especially
the nearshore waters during the afternoon sea breeze. Seas will
run 2 to 4 ft, but may see some 5 fters in outer waters.

LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 300 PM Thursday...Western Atlantic High Pressure will
bring increasing S winds ahead of a cold front. S winds Sun and
Sun night will be increasing to 15 to 20 kt. Seas will increase
to 4 to 6 ft by early Mon morning.

S to SW wind speeds will increase further Mon and Mon night, up to
20 to 25 kt as seas build to 5 to 8 ft. Then in the wake of the
front Tue, developing offshore winds will trend lower. The offshore
trajectories will knock seas down and we should drop below Small
Craft Advisory levels by Tue eve.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...Coastal Flood Advisory until 1 AM EDT Friday for NCZ107.
MARINE...None.

&&

$$
SYNOPSIS...
NEAR TERM...TRA
SHORT TERM...RGZ
LONG TERM...RJD
AVIATION...TRA
MARINE...


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