Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 251827

Area Forecast Discussion
National Weather Service Wilmington NC
123 PM EST Sat Feb 25 2017

Warm air will prevail across the Carolinas today. A cold front
approaching from the west will move off the coast this evening.
Cooler and drier air high pressure will spread into the area
tonight and persist through Monday. Shower chances will increase
Monday night and early Tuesday as a warm front lifts north
across the area. Much warmer temperatures will follow the front
Tuesday and Wednesday before the next cold front moves offshore
Thursday. Temperatures will drop to near to slightly below
normal Friday as a cooler and drier air mass builds over the


As of 1230 PM Saturday...Unfortunately, fog issues are not
behind us. The low level winds complements of a sea breeze with
winds from the S to SSW helping to push the sea fog partially
onshore the local beaches during this aftn. Extending from
Holden Beach south across Myrtle Beach and Murrells Inlet to
the mouth of Winyah Bay. The low level flow will become more SW
and eventually WSW this aftn helping to punch in some lower sfc
dewpoints off the coast basically detouring the onshore movement
of the sea fog. It may take a little longer for the Brunswick
County Beaches due to the parallel flow and coastline
configuration but in the end the lowering sfc dewpoints moving
off the mainland will help demise the sea fog. No changes needed
for aftn max temps.

As of 915 AM Saturday...All fog issues should be behind us now.
Latest sat imagery via IR and Vis channels indicate generally
mostly sunny skies with any leftover thin low stratus burning
off rather quickly. Clouds ahead and associated with the
eastward moving cold front will begin pushing into the area by
mid-day and progressing across the FA this afternoon and off
the Carolina Coasts early this evening. Limited moisture avbl
for low level cu/sc and mid level altocu. Latest model trends
indicate this limited moisture to scour out even more-so as it
progresses east in association with the cold front. Latest HRRR
indicates even a drier scenario and thus as a result will keep
a dry fcst with POPs below 15 percent. Not a true downslope
trajectory within the atm column today, however with a late Feb
sun equivalent to a mid to late October sun, should see
widespread 80+ degree readings away from the immediate coast.
Model 1000-500mb thicknesses in the low 560s and 850mb temps at
+ 10 to 12 degrees C and a good dose of insolation, all aiding
these warm Spring-like max temps in late Feb. A return back to
reality to occur this evening with the passage of the cold front
off the Carolina coasts this evening. Sfc pg tightens with SW
winds veering to WSW-W and becoming gusty as the cold front
pushes closer this aftn. After the CFP, CAA will be in full
force later this evening and overnight under active NW winds,
gusty for several hours immediately after the CFP itself.

As of 430 AM Saturday...Surface observations and 11-3.9 micron
difference satellite imagery suggest the area of dense fog
across eastern South Carolina is expanding and may be here
to stay for several hours. A dense fog advisory has been issued
for Georgetown, Horry, and Williamsburg counties until 9 AM.

One final day of unseasonably warm temperatures is expected
before a cold front brings us back to reality tomorrow. Today`s
highs are expected to reach the lower 80s inland, with 70s
closer to the ocean due to cool nearshore water temperatures.
Southwesterly winds will increase today ahead of the front,
likely gusting to over 25 mph this afternoon.

Record highs today, February 25...
Wilmington               81 set in 1930
Florence                 78 set in 1977
North Myrtle Beach       77 set in 1949

Precipitation potential is low today owing to shallow moisture
depth, a capping inversion between 7000-10000 feet AGL, and
virtually all of the upper dynamics shearing out far to the
north. I do expect there will be plenty of cumulus and even
towering cumulus around late this morning into this afternoon,
however the lid of warm air around 7000 feet should stop these
updrafts from becoming taller. The latest several HRRR runs look
very reasonable showing a line of sprinkles racing eastward
across the eastern Carolinas this afternoon between 1-4 PM.
Relatively shallow convective cloud depths and fast forward
movement should keep precip totals in the trace category for
most locations. Better precip potential will exist across the
northern half of North Carolina where moisture depth will be
greater and the warm air cap will be less prevalent, allowing
for greater convective depth.

Behind the cold front this evening, winds will shift
northwesterly as much colder and drier air moves in. By morning
lows should reach the lower to middle 40s, with some upper 30s
possible west of I-95.


As of 300 AM Saturday...High pressure centered over east
Tennessee on Sunday morning will move over the area Sunday
afternoon, then offshore Sunday night. Even with full
sunshine highs will only barely reach 60 degrees on Sunday,
slightly below normal and the coolest we`ve been since
February 16th. Good radiational cooling conditions with the
high just offshore Sunday night should allow temperatures to
fall into the 30s away from the beaches. It`s not impossible
some of the normally colder interior locations could see some
patchy frost.

Southeasterly return flow behind the departing high will
strengthen Monday. An approaching positively-tiled upper
disturbance will encounter the low-level warm advection across
the Carolinas Monday night, leading to cloudy skies and an
increasing potential for showers. PoPs have been increased to
50-60 percent for what should be a fairly light precipitation


As of 300 AM Saturday...Warm front in the vicinity Tue morning
will lift north of the area, taking the bulk of the showers
ongoing at the start of the period with it. Weak mid level
ridging expands north Tue and Wed as Bermuda High builds back
west. Although mid level subsidence and dry air aloft will be
present, a warm and moist boundary layer may allow for at
least a few afternoon showers each day, especially along the
sea breeze. Temperatures will be well above normal with highs
approaching 80 and lows around 60. Strong cold front is driven
across the area late Wed night/early Thu, accompanied by showers
and isolated thunderstorms. Morning timing of fropa will limit
available instability but the front will have plenty of forcing
associated with it. Moisture return ahead of the front is
limited which will affect storm coverage and rainfall totals.

Strong cold advection follows the front with temperatures
dropping in the afternoon Thu. Winds at the top of the mixed
layer will be around 30 kt with RH aloft dropping into the
single digits. Mixing could lead dry and breezy conditions Thu
afternoon. Canadian high continues to build in from the
northwest Fri with temperatures dipping a little below normal
for the end of the period.


As of 18Z...Southwest flow will remain gusty as winds veer to a more
westerly direction as cold front approaches from the west. A small
area of sea fog crept into the Myrtles as the winds backed to a more
southerly direction. This will only last for an hour or so and will
move out of terminals as winds shift back to a more SW direction.
The cold front will cross the terminals without any restrictions to
TAFs. Winds will pick up out of the west just ahead of the front
late this afternoon, with fropa expected this evening. Moderate
northwest flow tonight will become northerly and lighten by 08-
10z in strong CAA.

Extended Outlook...VFR. VSBY and ceilings lowered to MVFR/IFR
with pcp Mon night into Tues and again with SHWRs on Wed.


As of 1245 PM Saturday...Well the sea fog issues have re-
appeared. Given sat imagery and local obs, have issued an
update to the CWF as well as issuing a MWS for patchy sea fog.
The local sea breeze along the immediate coast has been aiding
the sea fog development and partial onshore movement. With time,
the low low level winds will become more SW and WSW this aftn
keeping any sea fog off the coast with the exception of
Brunswick County. Lower dewpoints will begin pushing off the
mainland this aftn and especially tonight after the CFP. Will
see the sea fog diminish in coverage later this aftn, especially
nearshore, and the remainder of the waters this evening.

As of 1000 Am Saturday...The fog issues earlier this morning
along the immediate coast have faded away. Sfc dewpoints may
increase into the 60s across the local waters. However SSTS have
rebounded into the low 60s, well above the climo norm. Thus,
the difference between the 2 temps are not conducive for sea fog
to develop today. The fog earlier was land-based that affected
the immediate coast, inlets and the Intra Coastal Waterway.

The sfc pg will tighten ahead of the approaching cold front
and yield increasing SW to WSW winds to SCA values across the
ILM NC waters, and SCEC thresholds for the ILM SC Waters. Winds
will veer to the NW after the CFP this evening and persist thru
the remainder of the night. The CAA surge will combine with the
tightened gradient to produce SCEC thresholds for the SC Waters
with 15 to 20 kt with gusts up to 25 kt. For the NC Waters,
winds will increase to 20 to 25 kt and hold thru the night.
Significant seas will run a healthy 3 to 5 ft SC Waters and 3 to
6 ft NC Waters. The ESE 11 second period ground swell has
peaked earlier this morning, however it will remain a dominant
force today and may equal out with locally produced wind driven
waves tonight and beyond.

As of 430 AM Saturday...NWS Charleston relayed a report from
the Charleston pilot boat around 230 AM indicating visibility
was around 1 mile at a distance of 10 miles offshore. This
region of marine fog appears to be crawling northward along the
South Carolina coast according to 11-3.9 micron difference
satellite imagery. Low visibilities inland at Georgetown and
Conway, SC also imply the area of dense fog is expanding. A
marine dense fog advisory has been issued for our South
Carolina coastal waters until 9 AM. Southwesterly winds should
be increasing by then, hopefully pushing the fog farther out to

The Carolina coastal waters are in a region of very light winds
between two regions of low pressure: one several hundred miles
east of the Outer Banks, and the pressure trough surrounding a
cold front over Tennessee. As the front approaches the region
later today, southwesterly winds will increase to 15-20 kt. The
front should move offshore and across the coastal waters this
evening, followed by gusty northwest winds overnight as colder
air builds in.

Buoys are still showing a significant easterly swell affecting
the waters. Seas at Frying Pan Shoals are nearly 7 feet,
entirely in a 9- second easterly swell. This swell will diminish
only slowly today, but increasing short period wind chop may
make boating conditions rather unpleasant. The Small Craft
Advisory has been extended for the NC waters through tonight,
and an exercise caution headline will be posted for the SC
waters as soon as the advisory expires there.

As of 300 AM Saturday...High pressure centered over Tennessee
on Sunday morning will move overhead Sunday afternoon, then
offshore Sunday night. Veering winds Monday into Monday night
will develop as the high moves farther offshore.

As of 300 AM Saturday...Warm front in the area Tue morning
lifts north as Bermuda High expands west. Southwest flow will
persist through the forecast period with speeds 10 to 15 kt on
Tue. Gradient tightens up Wed, ahead of approaching cold front,
with speeds increasing to 15 to 20 kt by midday Wed.
Seas 2 to 4 ft Tue into Wed build to 3 to 5 ft later Wed.


MARINE...Small Craft Advisory until 6 AM EST Sunday for AMZ250-252.


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