Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
1007 PM EST Tuesday Dec 1 2015
a cold front approaching from the west will move through the area
Wednesday afternoon and night...followed by cooler and drier
weather through the weekend. Another upper trough will move into
the southeastern states early next week and bring another chance
of rain to the region.
Near term /until 7 am Wednesday morning/...
main near term concern again tonight is possibility of dense
fog. Areas of dense fog beginning to redevelop across the northern
forecast area. Latest high resolution models suggest areas of dense fog to
continue northern forecast area...possibly expanding into central forecast area later
tonight...with some uncertainties about the southern
midlands/csra...as boundary layer winds begin to increase from the
SW ahead of the approaching front. Issued dense fog advisory for a
portion of the northern forecast area...and will expand elsewhere later
tonight if/when needed. Otherwise...most precipitation associated
with the approaching front is expected to remain mainly north and
west of our forecast area tonight.
Short term /7 am Wednesday morning through Thursday night/...
a weak surface low will be lifting northward along the cold front
over western North Carolina Wednesday morning with the front
extending southwestward through far northwestern South Carolina.
Precipitation should be west of the forecast area along the front
and will have a strong gradient in probability of precipitation from northwest to southeast
Wednesday morning. Widespread stratus event expected Wednesday
morning but as deeper southerly flow develops ahead of a digging
shortwave trough beneath the Midwest upper low...increasing
southerly low level flow should begin to scour out the lower clouds
and aid in warm air advection.
As shortwave energy pushes into the Tennessee Valley and southern
Appalachians on Wednesday it will drive the cold front eastward and
cross the area late Wednesday into Wednesday night. Latest model
guidance is suggesting a wave lifting northward over the area
along the front on Wednesday that could bring a chance for more
significant rain than previously forecast although some timing
differences lead to uncertainty in this scenario. However...will
increase the probability of precipitation across the area to likely and bump up the
rainfall amounts a bit especially in the southeastern midlands.
Instability continues to look meager with forecast lifted index
values remaining around -1c to -2c but will continue with the
mention of slight chance thunder. Expect temperatures to warm
considerably across the eastern half of the forecast area where
more sun and less rain expected through much of the day. Highs
will range from the upper 60s west to middle 70s east. Overnight lows
Wednesday night will be driven by steady winds resulting in a
mixed boundary layer and cold advection...with lows forecast in
Long term /Friday through Tuesday/...
generally quiet weather expected during the extended forecast period
with dry surface high pressure building over the area this weekend
into early next week.
Models are in good agreement in showing shortwave energy diving
southeastward across the Ohio Valley Friday and moving off the middle-
Atlantic coast on Saturday...while surface high pressure ridges down
the East Coast. Forecast soundings and time heights indicate a very
dry airmass in place with precipitable water values at or below 0.25
inches throughout the weekend. Temperatures over the weekend will be
near normal values with highs in the upper 50s to lower 60s and lows
in the middle 30s.
Uncertainty increases early next week with a divergence of the
GFS/European model (ecmwf) in handling a cutoff low moving eastward across the middle
of the country. The GFS strengthens and dives the cutoff low
southeastward over the forecast area by Tuesday morning leading to
the development of a strong coastal low...while the European model (ecmwf) is much
further north and weaker with a more eastward track of the upper
low. The different solutions would result in drastically different
weather and given the uncertainty will opt to continue with a
Aviation /03z Wednesday through Sunday/...
high clouds obscuring some of the lower clouds and fog across
portions of the County Warning Area. Based off of surface observation however...it appears
as if the lower ceilings and fog are situated along a northeast to
southwesterly line from just north of Cheraw...to Fairfield...to
the western portions of Lake Murray...to just west of Augusta.
IFR/LIFR conditions occurring along and west of that line at this
time. Areas just off to the east are seeing VFR conditions.
Depending on the movement of the denser wedge...all taf sites
would be expected to drop back down into IFR/LIFR conditions later
tonight as the boundary moves slightly eastward. Confidence is
moderate in this redevelopment of LIFR/IFR conditions. As such
will bring all terminals down to LIFR by 06z...lasting through
Expect conditions to improve to MVFR by 16z. However models
showing rainfall pushing through the forecast area between 18z-
22z...so will continue with MVFR/IFR conditions with the expected
rainfall. Winds through the period will be variable at 5 knots or
less overnight. Winds then become more southwesterly on Wednesday
and increasing to around 10 kts.
Extended aviation outlook...no significant aviation concerns
SC...dense fog advisory until 10 am EST Wednesday for scz015-020-