Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
158 PM EST sun Dec 21 2014
a frontal zone will remain near the southeast coast through
Tuesday. A series of low pressure systems will move northeastward
along the front...keeping weather unsettled. A strong cold front
approaching from the west will move through the forecast area late
Wednesday or Wednesday night.
Near term /through tonight/...
sub-tropical plume of moisture extending from central Mexico to
the southeastern states continues to be evident on the water vapor
imagery this afternoon. Visible imagery shows that skies cleared a
bit across the central and northern midlands allowing temperatures
to rise into the middle 50s. Isentropic lifting will increase late
afternoon into early evening in response to the approaching
shortwave from the Gulf Coast.
Light rain expected to develop and move northward into the
forecast area from the south around sunset. Isentropic lift
maximizes over the forecast area during the 03z-09z time frame and
the area falls within the right entrance region of a strong 120+
knot upper jet throughout much of the night...aiding in forcing
for precipitation. Leaned towards the higher met pop guidance and
will carry categorical probability of precipitation for the entire forecast area...with
the highest probability of precipitation centered around the 06z-09z time frame.
Temperatures will fall into the lower to middle 40s limited by
wetbulb temperatures. Despite the high probability of precipitation overnight...total
rainfall amounts are expected to be light at generally a tenth of
an inch or less...with some isolated amounts closer to a few
tenths of an inch.
Short term /Monday through Wednesday night/...
models showing the bulk of the rainfall pushing north of the County Warning Area
early Monday morning...and will have decreasing probability of precipitation during the
morning. Still expecting scattered rainfall with some drizzle
through the day. Wedge will hold strong Monday through Monday
night. With plenty of cloud cover and northeast winds...temperatures
will not recover much through the day Monday...with readings
remaining mainly in the 40s. Overnight lows Monday night will
also be in the 40s. Deeper moisture will return to the County Warning Area again
during the day Tuesday...and with this increase the area will see
an increase in probability of precipitation. Wedge may diminish and weaken late in the day
Tuesday...which would allow temperatures to reach the 50s. With
The Wedge breakdown and the expected return of warmer
air...temperatures Tuesday night will not drop much and may
even rise slowly through the night. Categorical probability of precipitation through
Tuesday night. Stronger cold front is poised to move into the
region Wednesday. At this time the upper support remains behind
the surface cold front...with the surface front moving through
Wednesday evening. Widespread rainfall will move through the
region early in the day Wednesday...then should see a decrease in
probability of precipitation late Wednesday into Wednesday night. With the warm air ahead
of the cold front...Wednesday should be the warmest day of the
period as temperatures rise into the upper 60s to lower 70s. Can
not rule out isolated thunder on Wednesday if the upper support
can catch up with the surface front...but at this time the
confidence is not high enough to mention. Winds from Wednesday through
Wednesday night will become strong and gusty...with wind gusts of
20 miles per hour possible.
Long term /Thursday through Sunday/...
return to more seasonable temperatures behind the front. The
models continue to show a dry airmass for Christmas day. Winds
will remain breezy and gusty on Christmas day...then the gradient
weakens by Thursday evening.
Moisture may increase associated with another cold front moving
into the area Saturday into Sunday.
Aviation /19z Sunday through Friday/...
VFR conditions becoming MVFR after sunset...and IFR/LIFR late
tonight through Monday morning.
Skies have cleared a bit this afternoon but increasing clouds
expected late this afternoon with lowering ceilings to MVFR around 00z
ags/dnl/ogb and by 03z at cae/cub as isentropic lift increases
ahead of approaching shortwave energy. Light rain should
overspread the terminals from south to north overnight. Ceilings
expected to drop to IFR after 06z with the rainfall and increasing
wedge conditions. Persistent southwesterly flow aloft atop the
northeasterly low level flow will keep wedge conditions in place
after 12z which will result in lowering visibilities in drizzle and light
rain with IFR/LIFR ceilings.
Extended aviation outlook...widespread MVFR to IFR conditions
expected Monday through Wednesday evening as a series of systems
cross the region. Breezy conditions possible Wednesday afternoon
into Thursday morning.