Scientific Forecaster Discussion
fxus62 kilm 090905
Area forecast discussion
National Weather Service Wilmington NC
405 am EST Fri Dec 9 2016
cold high pressure will build across the area tonight into the
weekend, ushering in the coldest temperatures of the season. A
warming trend will follow early next week ahead of the next
front. This cold front may stall over or just south of area on
Tuesday and may linger across the area producing unsettled
weather through mid week. A stronger cold front will move
through by Thursday with cold and dry high pressure building in
Near term /through tonight/...
as of 330 am Friday...an airmass with origins in the Arctic
will filter into the forecast area through tonight, with the
coldest air at 850 mb reaching -4c to -7c by late this evening.
Time- height cross sections show a dry column with westerly
flow, so expect abundant sunshine today, but unseasonably cool
with highs only reaching the mid 40s. A light north-northwest
wind should persist through most of the night tonight, although
some spots may briefly decouple inland. Low temperatures range
is expected to bottom out in the low to mid 20s, with the
highest end of that range along the immediate coast.
Short term /Saturday through Sunday night/...
as of 330 am Friday...850 mb temps will be 2-3c warmer Saturday
than Friday, however given the cold start, high temperatures
are expected to be similar to Friday, reaching only into the mid
40s. A deep layer of dry, westerly flow should result in
another day of mostly sunny skies. Saturday night US shaping up
to be a very good radiational cooling setup, so will continue
with a minimum temperature forecast leaning toward the low end
of the MOS spectrum.
Zonal flow will push the surface high pressure off the mid-Atlantic
coast Sunday and the airmass should begin to moderate. There is, as
usual, uncertainty with timing the inland progression of the coastal
front on Sunday, and although high temperatures are currently
forecast to reach into the upper 50s along the coast, temperatures
may remain significantly lower than that for much of the day until
the coastal trough moves inland. There is also some disagreement
between the GFS and European model (ecmwf) in terms of precip potential on Sunday, so
hopefully these will come into better agreement with 12z run. But at
this time, believe it is warranted to include a low pop across the
southern coastal County Warning Area and just offshore, with increasing chances
mainly east of the I-95 corridor Sunday night as the trough lifts
Long term /Monday through Thursday/...
as of 330 am Friday...southerly flow will increase as gradient
tightens ahead of approaching cold front on Monday. This will
pump plenty of warm and moister air into the Carolinas. Dewpoint
temps will return into the 50s to around 60 with temps reaching
up to the mid 60s to around 70. Best chc of pcp will come later
on Monday ahead of cold front, though not expecting too much in
the way of quantitative precipitation forecast.
The broad, almost zonal flow behind this front may not drive the
front too far south on tues. The GFS is more aggressive pushing
it through South Carolina by tues morning, while the European model (ecmwf) shows
it bisecting our forecast area from west to east tues morning as
weak low pressure develops along it. This would make the
difference of a cool dry day on tues vs. A potentially cloudy
and wetter day for tues. The GFS does bring this front back
north as a warm front by Wed. Overall expect potential for
unsettled weather through mid week before a strong cold front
sweeps through on Thursday scouring out the clouds and pcp late
thurs into Fri.
Aviation /06z Friday through Tuesday/...
as of 06z...high confidence in VFR conditions over the next 24
hours. Arctic high pressure over the plains states will build
eastward, maintaining a northerly breeze across the Carolinas
today. Winds could gust to 15-17 knots after daybreak from
330-360 degrees. Cirrus at fl200-250 should thin out this
morning with sky clear expected this afternoon and tonight.
near term /through tonight/...
as of 330 am Friday...strong northerly gradient winds will
persist across the waters into this afternoon as high pressure
builds offshore. These winds will maintain 5-6 foot seas in the
10-20 nm range into mid afternoon. The Small Craft Advisory will
remain in effect today. It is currently set to expire at 6 PM,
and but based on latest data, it may be able to be dropped a few
hours earlier. Will let the day shift make that call after a
look at 12z guidance.
Short term /Saturday through Sunday night/...
as of 330 am Friday...high pressure center will remain over
inland NC, and northerly flow will continue Saturday, although
lighter considering the weaker gradient. Direction will become
northeast Saturday night and Sunday as a coastal trough
develops, and this will introduce the potential for developing
showers by Sunday. Sunday night, the trough will lift north, and
southerly winds will become southwest by late Sunday night.
Seas are expected to build during the night Sunday night, and
may reach 4-5 feet towards Monday morning.
Long term /Monday through Tuesday/...
as of 330 am Friday...southerly winds will increase ahead of
approaching cold front through Monday. This will push seas up
from 3 to 5 ft in the morning to 4 to 6 ft, reaching Small Craft Advisory
thresholds as gradient tightens ahead of cold front. Winds will
veer around to the north by tues as cold front drops south,
diminishing down to 10 to 15 mph with seas subsiding down to 2
to 4 ft. This front may stall across or just south of the waters
on tues and may linger over the waters producing more variable
winds and seas through mid week.
Marine...Small Craft Advisory until 6 PM EST this evening for amz250-