Scientific Forecaster Discussion
fxus62 kcae 092306
Area forecast discussion
National Weather Service Columbia SC
606 PM EST sun Dec 9 2018
low pressure just south of Cape Fear this afternoon will
continue to move off to the northeast tonight and Monday. The
low will move farther away from the forecast area Tuesday as
high pressure builds into the area from the west. This high will
be over the area Wednesday. A warm front will approach Thursday
with low pressure back in the region Friday.
Near term /until 6 am Monday morning/...
tonight...an elongated positively tilted upper trough will
remain north of the area through this evening then begin to sink
south over the northern midlands overnight. A gradual warming
of the boundary layer and surface temperatures through the
evening will result in light rain for ptype through 06z then as
the mid and upper levels of the thermal profile cool there is a
chance for some light snow/sleet that may mix with rain or stand
alone later tonight. The latest short models (hrrr/arw) support
an increasing probability of precipitation after midnight
mainly north of I-20. The intensity of the precipitation is
expected to be light enough that no significant accumulations
are expected, less than inch but that is another reason we are
keeping the advisory going.
Short term /6 am Monday morning through Monday night/...
another upper trough moving through the mid MS valley early Monday
will phase with the sinking upper trough over the southeast states
on Monday afternoon and then shift south and east of the forecast
area Monday night. There could still be some mixed precip type
snow/sleet/rain in the northern midlands advisory area early Monday
but the boundary layer is expected to warm enough that all precip
should turn to rain during the day although some sleet may still mix
in at times Lancaster/Chesterfield counties. The thermal profiles
cool further Monday night which would support snow/rain mix across
the entire forecast area though no accumulation is expected outside
of the advisory area and even there very little accumulation
expected due to increasing drier air in the lower layer between
925mb and 800mb. High temperatures on on Monday will be quite cool
and well below normal ranging from the upper 30s northern midlands
where some cold advection off snowpack over NC may have some impact,
to the lower 40s in the csra and southeast midlands. Lows Monday
night will fall into the upper 20s to lower 30s.
Long term /Tuesday through Sunday/...
there may be some lingering moisture and instability associated
with the upper trough early Tuesday. Significant lift should be
ahead of the system and east of the forecast area. Moisture
should be shallow. The snow shower chance was too low to include
in the forecast. Further drying is forecast Tuesday afternoon
and night behind the upper feature and ahead of surface ridging
building into the area from the west. The ridging is forecast to
be over the region Wednesday. The GFS and European model (ecmwf) show a moisture
increase ahead of a warm front Thursday. Deeper moisture is
depicted holding west of the forecast area until Thursday night.
We forecasted chance pops late. There should be enough warming
for all liquid precipitation. There was consistency in deep
moisture Friday associated with a low pressure system in the
region. There has not been consistency in the position of
greatest shear and instability. The GFS was farther north with
the track of the low and indicated much more warming in the
forecast area. We followed a guidance average for the
temperature forecast for now. We also kept showers in the
forecast instead of thunderstorms because of the uncertainty.
The GFS indicated drying over the weekend, but the European model (ecmwf)
indicated lingering low pressure and associated moisture so we
kept chance pops in the forecast.
Aviation /00z Monday through Friday/...
restrictions expected through the 24 hours taf period.
Low pressure just south of Cape Fear will continue to slowly
move to the northeast over the next 24 to 48 hours. Current
satellite imagery shows extensive MVFR/IFR cloud cover across
the region remaining in the wake of the system. Model time
sections Show Low level moisture remaining over our taf sites
through Monday night/early Tuesday morning. As energy aloft
slowly moves across we cannot rule out scattered areas of light
precipitation overnight at cae/cub. Precip will be light as
available moisture is shallow and confined to the low levels.
As the low departs pressure gradient continues to relax...dropping
windspeeds and allowing fog/drizzle to develop. Conditions at
times may deteriorate further in light precipitation and fog after
06-12z to LIFR. Lower confidence at this time for exact timing.
Temperatures are expected to remain slightly above freezing
during the period and any winter precipitation concerns for
airfield surfaces are not expected.
Extended aviation outlook...continued MVFR/IFR restrictions
expected through Monday night...with potential for light
precipitation. Potential for a round light rain and snow mix
Monday night at cae/cub/ogb.
rainfall amounts of 2 to 4 inches across the upstate and
midlands including over many of the rivers headwaters will
continue to work downstream through each basin into next week.
Although some additional light precipitation is possible through
Monday night, it will not impact the Current River forecasts
further. Minor flooding will continue along Stevens Creek at
Modoc through the next 12 to 18 hours. However, along the
Congaree River, high flows will continue through much of the
week. A flood advisory will continue along the Congaree River at
Columbia over the next few days. River flood warnings will
continue at Carolina Eastman and the Congaree National Park-
Gadsden through much of the upcoming week. Moderate flooding
will occur at Carolina Eastman with minor flooding at the
Congaree National Park- Gadsden. Finally...minor flooding is
expected along the Enoree river at Whitmire. Those living along
all area rivers should be aware of high flows through much of
SC...Winter Weather Advisory until 7 PM EST Monday for scz015-016-