Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington NC
634 PM EST Tuesday Feb 9 2016
this cold airmass will be reinforced by the passage of a dry
Arctic front Wednesday. The area will remain dry with below
normal temperatures for the remainder of the week. Another cold
front will cross the area Friday night with Arctic high pressure
moving over the Carolinas for the weekend...bringing the coldest
air of the season thus far. Temperatures will begin to moderate
early next week as the center of the Arctic chill moves away from
Near term /through Wednesday/...
as of 630 PM Tuesday...a very cold airmass is rushing into the
Carolinas this evening. Tonight's temperatures at virtually any
level will soon be some of the coldest we've seen this winter
season: 850 mb around -10c...700 mb almost down to -20c...and 500
mb near -30c.
Steep lapse rates plus a little residual moisture in the deeply
mixed boundary layer are combining to produce widespread
stratocumulus clouds. Radar is showing some light echoes (10-20
dbz) particularly near Lumberton and Fayetteville. Some snow
flurries could reach the ground over the next few hours across
the northern sections of the Pee Dee region and interior southeast North
Carolina. Isentropic motion through the moisture-bearing layer
(280k theta) is downward so this really shouldn't be more than
flurries. By midnight the moisture should be thinning from the top
down with skies gradually clearing.
Despite such cold air aloft the boundary layer should remain
rather well mixed overnight with a tight pressure gradient
continuing overnight. This will prevent any significant
nocturnal/radiational inversion from developing and lows should
only reach the upper 20s. Both GFS and NAM MOS appears to be 2-3
degrees too cold. Wind chills will fall to around 20 overnight.
Short term /Wednesday night through Thursday night/...
as of 200 PM Tuesday...a large trough across the eastern third of
the nation will be slowly lifting north through the forecast period.
At the surface...an Arctic front will traverse the area Wednesday.
Thus...although heights will be rising aloft...at the surface...
the cold air will be strongly advecting into the area...
reinforcing the winter chill. The well below normal temperatures will
feel even colder Wednesday with the gusty west winds up to 20 to 30 miles per hour.
Highs will be around 40 Wednesday and lower to possibly middle 40s Thursday.
Wind chill values will be as low as the teens this period and even
during the day it will feel as if it were only in the 30s...near
the freezing mark Wednesday. Lows will be in the lower to middle 20s
although some clouds late Thursday night in association with low
pressure passing to our S may bring more in the way of clouds
which could complicate the low temperature forecast. A few spots could
drop into the upper teens Wednesday night if the wind sufficiently
diminishes near daybreak to allow better radiational cooling. It
will be very dry with dewpoints dropping into the teens with even
a few single numbers possible. This dry air will be beneficial
given the ground is as wet as it is.
Long term /Friday through Tuesday/...
as of 200 PM Tuesday...long term GOES from cold to really cold and
then back to just cold. Friday brings cyclonic flow aloft around
large vortex north of New York state. A small pocket of energy
distinguishes itself from the main belt of northwest flow and manifests as
a sheared out shortwave. The airmass will be much too dry to support
meaningful precipitation chances but since mainly northern zones could be
cool enough for ptype issues will carry minimal probability of precipitation for what will
end up likely as sprinkles/flurries, if anything at all. Upper low
sinks south and eastward over the weekend allowing Arctic air to
penetrate the region plunging 850mb temperatures to -10 to -15c roughly
south to north on Saturday and/or Saturday night. The coldest of the
cold thus appears to be Saturday night and Sunday while even though
some recovery may be underway Sunday mixing will be the poorest.
Late in the period finds weaker upper troughiness and a bit further
west leading to US clouding up locally and increasing rain chances.
Our temperature moderation should be quite hindered by all of the
cloudiness but there is some guidance that has US back to climatology by
Aviation /00z Wednesday through Sunday/...
as of 00z...large upper low north of the area will continue to
inject cold Arctic air into the region through the end of the
forecast period. High stratocu ceiling will prevail through much
of the overnight hours...perhaps scattering a few hours after
midnight. Gusty west winds will diminish for diurnal reasons in a
couple of hours. Wednesday...continued cold with falling
dewpoints. Another stratocu ceiling is possible just before maximum
heating. Cold air advection will bump winds up again after
Extended outlook...predominately VFR. Expect west to northwest winds gusting
to 20 to 30+ knots Wednesday into early Thursday...and again late
near term /through tonight/...
as of 630 PM Tuesday...a very cold airmass will build across the
Carolinas tonight...pushed by Canadian high pressure moving
southeastward through the plains states. All models show wind
speeds not really diminishing much at all overnight with westerly
winds 20-25 knots gusting to 30 knots...then gradually veering a little
more northwesterly with time. A westerly wind is a short fetch
across most of the coastal waters and seas are generally 3-6
feet...however along the Brunswick County coast where a west wind
can pick up a 50 mile long fetch seas are likely 7-8 feet near
Frying Pan Shoals. These waves should begin to diminish late
tonight as the direction veers a little more northwesterly.
Short term /Wednesday through Thursday night/...
as of 200 PM Tuesday...the pressure gradient becomes pinched for
a time Wednesday with the passage of Arctic front. Strong cold and dry
advection will lead to strong Small Craft Advisory conditions. The
strongest winds this period are expected Wednesday afternoon and
evening...up to 25 to 30 knots with gusts to near gale force. A Small
Craft Advisory continues and is in effect through 6 am Thursday. The
wind direction will be from the west and west-northwest while winds are
strongest. This strong offshore flow will flatten seas near shore
while allowing seas across the outermost waters to remain near 5
to 7 feet. Wind speeds late Wednesday night and Thursday will drop to 15 to 20
knots and then to around 10 knots or less for the remainder of the
period. The direction will veer from west-northwest to northwest Thursday evening and to north or
NE Thursday night. Seas will be mainly 2 to 4 feet Thursday and 2 feet or less
Long term /Friday through Sunday/...
as of 200 PM Tuesday...wind and seas both pretty light on Friday
though there is a bit of uncertainty regarding wind direction as a
flat wave of low pressure may ride by. Cold air then surges
strongly on Saturday and a moderate northwest flow develops that may
necessitate a brief scec. As the center of the high moves over the
middle-Atlantic local flow will veer and abate. Seas will also be
trending downward in size.
as of 1230 PM Tuesday...guidance still calling for another round
of coastal flooding at downtown Wilmington. Confidence is rather
high considering the past few cycles and levels. Went ahead and
issued the advisory for this evening.
NC...coastal Flood Advisory until 1 am EST Wednesday for ncz107.
Marine...Small Craft Advisory until 6 am EST Thursday for amz250-252-