Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
933 PM EST Friday Feb 12 2016
an Arctic cold front will cross the area late tonight and bring
the coldest air of the season for the weekend. A warmup will
begin Monday. Temperatures will rebound to normal values ahead of
a strong low pressure system which will bring good rain chances on
Tuesday. Seasonable weather will follow Wednesday through Friday.
Near term /until 6 am Saturday morning/...
as of 930 PM Friday...surface low pressure is now 250+ miles east
of Cape Hatteras and is surrounded by an impressive area of
thunderstorms. The lightning detection network is counting over
800 strikes per 15 minutes offshore! This low and its associated
thunderstorm activity will accelerate out to sea tonight.
An Arctic cold front currently extending from Charlotte to just
west of Augusta Georgia will race eastward behind the departing
low...reaching the eastern Carolinas around midnight. We've
already lost the clouds across South Carolina and low level
moisture is thinning across southeast North Carolina as westerly winds
develop down to 925 mb.
Clouds should continue to diminish between now and
midnight...with pretty good radiational cooling conditions
allowing temperatures to dip into the upper 20s to lower 30s. Once
the Arctic front arrives...much drier air will punch in along with
steepening lapse rates. This will erase any radiational inversion
that manages to develop this evening...and counterintuitively
should create a ~5 degree rise in temperatures. Cold advection
will then drop lows back into the upper 20s to lower 30s again by
daybreak. This may seem excessively warm given the fact that 850
mb temperatures will be plunging below -8c by daybreak...but gusty
boundary layer winds and very steep lapse rates developing due to
cold advection behind the front should keep the boundary layer
Short term /6 am Saturday morning through Sunday night/...
as of 300 PM Friday...Arctic high pressure will be centered
across the northern Mississippi Valley at the start of the period.
This is the feature that will bring the coldest and driest air of
the season. As this Arctic high is building in...it will bring
gusty northwest to north winds 20 to 30 miles per hour. 850 mb temperatures will drop to around
minus 10 degree c and as cold as minus 10 degree c. At the
surface...high temperatures on Sat...even with sunshine...will struggle
to reach the 40 degree mark and across a good portion of the
area...it will fall short of 40. It will feel near or below
freezing all day and for much of the time...only in the 20s.
As the center of the Arctic airmass moves to the eastern third of
the nation...the coldest night is expected Sat night. Very low
dewpoints will allow plenty of room for temperatures to drop. We are not
forecasting the boundary layer to completely decouple which should
keep radiational cooling from maximizing. However... even with
that...we are forecasting lows in the teens to around 20. This will
be a double edged sword as the wind contribution will make it feel
as if it were only in the single numbers. It is likely a Wind Chill
Advisory will be required for most of the area Sat night.
Record lows/forecast for 2/14:
Wilmington: 5 degree set in 1899/18
Florence: 15 degree set in 1968/18
North Myrtle beach: 17 degree set in 1955/19
Then on sun...not much of a warmup. Temperatures are not expected to
recover out of the 30s and it may take until afternoon across a good
portion of the area before temperatures exceed 32 degree.
We should begin to see clouds increase Sun afternoon and Sun night
ahead of upstream southern stream system. As the center of high
pressure moves off the northeast US coast...a coastal trough may
begin to take shape. May see some light snow flurries or ice pellets
west of Interstate 95 during the early morning hours of Monday. Will
include a slight chance for this risk. These clouds will help to
insulate the area and combined with an onshore flow will keep lows
from dropping below the middle and upper 20s Sun night.
Long term /Monday through Friday/...
as of 300 PM Friday...low pressure system will be taking shape
across the Gulf states on Monday. This system will move east-NE
across the southeast riding across central North Carolina by Tuesday
morning. Center of low should remain west of local forecast area
keeping warm air in place over the coastal Carolinas. Winds will
pick up out of the southeast through Monday eventually veering to
the SW-west through Tuesday as system lifts off to the north. Moisture
through the column will increase through Monday with best moisture
and lift in place late Monday into early Tuesday. Therefore expect
clouds to thicken and pcp to increase with periods of moderate to
heavy rain overnight Monday into early Tuesday. Quantitative precipitation forecast may be upwards of
an inch by Tuesday morning.
Once this system pulls away on Tuesday...one more minor shortwave
rotating around the main middle to upper trough may produce some clouds
and low end pcp as it passes through mainly north overnight Tuesday
into early Wednesday morning. Otherwise expect dry weather Wednesday through
The southerly flow ahead of this low will produce a sharp rise in
temperatures across the area. 850 temperatures below 0c will warm to 8c bringing
temperatures back up toward normal on Monday and at or above through the
remainder of the week as very broad middle to upper trough shifts east
allowing heights to rise. Once trough axis crosses the coast early
Thursday...may see a brief cooling before 500 mb heights rise late Thursday
into Friday as ridge builds over the southeast. At the same time...surface
high shifts off the coast by Friday allowing for warmer southerly flow
to develop by Friday. Therefore may see a little dip in temperatures on Thursday
but overall warming trend through the week.
Aviation /00z Saturday through Wednesday/...
as of 00z...a mixture of VFR/MVFR/IFR this evening due to low ceilings
will improve to VFR overnight...continuing through the valid taf
period ahead of an Arctic cold front.
Latest imagery remains very quiet this evening as all precipitation
from earlier today has since dissipated...but latest observations
and satellite imagery continue to depict low to middle clouds moving
across the area. As a result...intermittent patches of low ceilings are
creating MVFR/IFR this evening. Do anticipate skies to gradually
clear into the overnight hours...giving way to VFR at all terminals.
On Saturday...VFR will prevail with nearly clear skies.
Northwesterly winds 5 to 8 kts tonight will increase to 10 to 15 kts
on Saturday with gusts near 25 kts. Will see gusts subside into
Extended outlook...predominantly VFR. Unsettled weather on Monday
and Tuesday with precipitation.
near term /through tonight/...
as of 930 PM Friday...low pressure is about 250 miles east of
Cape Hatteras and will move quickly out to sea tonight. An Arctic
cold front moving east through the NC foothills into the SC
mountains will race eastward...reaching the beaches between 2-4
am. Northwest winds 10-15 knots currently will increase to 20-25
knots toward daybreak behind the front. A Small Craft Advisory
remains posted. No significant changes have been made with this
Short term /Saturday through Sunday night/...
as of 300 PM Friday...will initialize with a marginal Small Craft
Advisory. As Arctic air builds across the waters...should see winds
to 20 to 25 knots and seas of 4 to 7 feet...highest across the outermost
waters with 7 feet restricted to the outermost northern waters.
Conditions should remain near of just above Small Craft Advisory
levels Sat night...then as the center of the high nears...winds and
seas will subside sun and Sun night. A coastal trough may develop in
close proximity Sun night. The wind direction will be north-northwest to north Sat
and Sat night and then veer to NE sun and then become east or southeast Sun
Long term /Monday through Wednesday/...
as of 300 PM Friday...deepening low pressure will ride across the
Gulf states into the Carolinas by early Tuesday and off the middle
Atlantic coast by Tuesday night. This system will produce increasing
on shore southeast winds on Monday up to 15 to 25 knots pushing seas
rapidly up from less than 3 feet early Monday up close to 8 to 10 feet
overnight Monday and possible increasing further as winds begin to
veer and strengthen further out of the S-SW by Tuesday morning. Small
craft conditions will develop by Monday evening. Seas may increase
further through Tuesday but winds will continue to veer as low lifts
off to the north allowing a stronger westerly off shore flow to
develop and keeping highest seas in the outer waters by Tuesday afternoon.
Wna shows peak in seas up near 11 feet near Frying Pan Shoals by
Westerly flow will continue through Tuesday night into Wednesday as it
diminishes in strength down to 10 to 15 knots. Expect seas to drop
down below Small Craft Advisory thresholds by late Wednesday.
NC...coastal Flood Advisory until 3 am EST Saturday for ncz107.
Marine...Small Craft Advisory from 5 am Saturday to 6 am EST Sunday for