Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
655 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/...
with plenty of low level moisture trapped below inversion...will
look for a repeat of low ceilings and dense fog overnight again.
Will gradually up the probability of precipitation during the 06z-12z period. Believe
there will be a sharp cutoff on the precipitation shield as 800 mb low level
jet of 40 kts between 06z-12z keeps eastward progress of precipitation and
cold front from progressing much. Models do show some light precipitation
out ahead of the front...but thinking is the period up until 12z
will be dry.
Overnight lows will be very mild for this time of year with lows
mainly in the middle 50s northwest to around 60 southeast portion of County Warning Area. Dense fog
advisory could again be posted during the 06z-12z time period.
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 /00z Wednesday through Sunday/...
model soundings show plenty of low level moisture trapped beneath
an inversion that will hold overnight and through the 12z-15z
time frame. Models do show an area of fog/stratus pushing into
the area from the southeast late tonight...so expect to see
redevelopment of LIFR/IFR conditions overnight...with dense fog
possible. Confidence is moderate to high in this redevelopment of LIFR/IFR
conditions. As such will bring all terminals down to LIFR in the
03z-06z time frame...lasting through 14z-16z Wednesday.
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