Scientific Forecaster Discussion
fxus62 kchs 142347
Area forecast discussion
National Weather Service Charleston SC
647 PM EST Thu Dec 14 2017
a dry cold front will push through Friday night before high
pressure returns Saturday and Sunday. Another cold front will
arrive Monday into Tuesday before shifting offshore on
Wednesday. High pressure should then persist into late week.
Near term /until 6 am Friday morning/...
early this evening: the main forecast issue will revolve around
the coverage and thickness of high clouds overnight. There is a
well defined band of upper level moisture that extends back to
the southwest all the way to the Pacific Ocean. There is a
trough and developing upper low across northern Mexico with a
strengthening 300 mb jet coincident with the moisture. This is
pumping plentiful cirrus into the region. Other than this cloud
cover though, conditions will be very quiet. No changes needed
to the going forecast other than for some edits based on recent
Short term /6 am Friday morning through Sunday/...
pretty high confidence this period with no significant weather
expected. Surface high pressure will prevail, although a dry cold
front will move through Friday night. Can't completely rule out a
shower Friday ahead of the front but it looks like deep low-level
dry air will be in place so we maintained a dry forecast. Also could
see a few showers later Sunday as moisture and low-level isentropic
ascent increase. High temperatures will be slightly above normal
Friday and Sunday and near normal Saturday. Low temperatures will
generally be near normal, which means near freezing well inland
Saturday and Sunday morning.
Long term /Sunday night through Thursday/...
cloud cover should expand over the southeast Sunday night with
increasing moisture and isentropic ascent occurring well ahead of a
cold front approaching the area. Chances of showers should arrive
late Sunday night and increase in coverage through Monday as a plume
of moisture characterized by pwats near 1.75-2.0 inches advects over
the southeast along/ahead of the slowly approaching front. Temps
could peak into the upper 60s to around 70 degrees on Monday despite
clouds and increasing shower coverage, mainly due to the strength
and position of the mid/upper lvl ridge of high pressure to the
southeast. Temps will remain mild Monday night and Tuesday while mid-
lvl energy continues to traverse the southeast before the main mid-
lvl trough axis and associated cold front shift over the area late
Tuesday into early Wednesday. For this reason, at least chances of
showers will be possible Monday night into early Wednesday before
dry high pressure returns behind the cold front shifting offshore.
Aviation /00z Friday through Tuesday/...
Extended aviation outlook: no significant concerns through Sunday
but restrictions are likely thereafter into at least early Tuesday
as deepening moisture increases the risk for low clouds and rain
with a cold front.
tonight: near term guidance indicates that a surface wave will
move from the foothills of the Carolinas east along the NC/SC
line tonight. A weak cold front associated with the wave should
remain generally west of the forecast area through tonight. The
pressure gradient in proximity to the wave and front is expected
to be limited to a single mb. Winds should favor a west-southwest direction
near 10 kts. Seas are forecast to range between 1-2 feet.
Friday through tuesday: expect a bit of a wind/sea increase behind a
cold front moving through Friday night but conditions should remain
below advisory levels. No significant concerns thereafter with high
pressure building in through Sunday, then conditions will go
downhill a bit as a cold front approaches the area.