National Weather Service United States Department of Commerce

 


385
FXUS62 KILM 251016
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
518 AM EST Sat Feb 25 2017

.SYNOPSIS...
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
area.

&&

.NEAR TERM /THROUGH TONIGHT/...
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.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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 event.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
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.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
As of 12Z...Fog/stratus will persist til 13Z, and should dissipate
pretty quickly between 13-14Z. Southwest flow is expected ahead of a
dry but moderately potent cold front. Winds will become more
westerly and gusty immediately ahead of the front late this
afternoon, with fropa expected this evening. Moderate northwest flow
tonight with cold air advection.

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

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
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
sea.

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.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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.

LONG TERM /TUESDAY THROUGH WEDNESDAY/...
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.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Dense Fog Advisory until 9 AM EST this morning for SCZ039-
053>056.
NC...None.
MARINE...Dense Fog Advisory until 9 AM EST this morning for AMZ254-256.
Small Craft Advisory until 6 AM EST early this morning for
AMZ254-256.
Small Craft Advisory until 6 AM EST Sunday for AMZ250-252.

&&

$$

SYNOPSIS...III
NEAR TERM...TRA
SHORT TERM...TRA
LONG TERM...III
AVIATION...43