Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
1215 am EST Friday Dec 19 2014
the pressure ridge extending through the Midwest will direct dry
air into the forecast area through Friday. Moisture will increase
Friday night ahead of low pressure tracking eastward along the
Near term /until 6 am this morning/...
high pressure remains across the region through the overnight
hours. Satellite showing strato-cumulus clouds advecting into the
midlands from the upstate SC and north Georgia. Models suggest
these clouds will thin out as they move to the east. Otherwise
expect mainly high clouds. Most guidance continues to come in
with the middle 30s for most areas...and see no reason why this
should not be close to what occurs.
Short term /6 am this morning through Saturday night/...
based on 18z guidance...and greater uncertainty for probability of precipitation Saturday
mainly across the north midlands...lowered probability of precipitation in that region
from categorical to 60 percent...
The models maintain the dry air mass Friday but show an increase
in moisture Friday night ahead of low pressure expected to track
along the Gulf Coast. The NAM...GFS...and European model (ecmwf) MOS have probability of precipitation less
than 10 percent through Friday with the chance increasing from
west to east Friday night. The models have trended slower moving
deeper moisture into the forecast area. Isentropic lift appears
weak and models have also backed off on the probability of precipitation for the area on
Saturday. Model precipitable water trending lower across the north
midlands and with large Standard deviation in the pop
guidance...lowered probability of precipitation in that region. Have continued with
increasing probability of precipitation Friday night into Saturday with highest probability of precipitation in
the csra and south midlands. Strongest isentropic lift/and
moisture flux in those regions. Weaker lift and lower precipitable
water in the north midlands suggests lower probability of precipitation. Drizzle expected
at times across the County Warning Area. Quantitative precipitation forecast amounts are expected to be less than
one quarter of an inch. We forecasted chance probability of precipitation mainly late as
short wave trough moves offshore. Model forecast soundings have been
consistent indicating liquid precipitation. Used the guidance
consensus for the temperature forecast Friday/Friday night. Expect
little temperature recovery Saturday because of cloudiness and
rain. Leaned toward just below the cooler side of the temperature
Long term /Sunday through Thursday/...
the models have trended with more moisture Sunday into Monday
with increasing isentropic lift over a Wedge Ridge. The GFS and
European model (ecmwf) MOS probability of precipitation have increased through the period and will continue
with a low chance probability of precipitation through Sunday with increasing probability of precipitation for
Monday. The temperature guidance may be too warm because of a
High moisture may continue Monday and Tuesday ahead of a warm
front with a deepening upper-level trough in the Mississippi
River valley. The warm front may lift north of the area ahead of a
strong cold front. The models have not been consistent with the
timing of these features but appear to be trending toward cold
frontal passage Tuesday night. Windy and dry conditions may
follow the front for Wednesday.
Aviation /05z Friday through Tuesday/...
VFR conditions expected during the next 24 hours.
Dry high pressure at the surface will continue through the period.
Satellite imagery shows clouds around 6kft moving in from the
west. Expect these lower clouds to dissipate over cae/cub and not
make it to ags/dnl/ogb. Increasing high clouds on Friday ahead of
the next approaching system. Light and variable winds overnight
will turn northeasterly for Friday. Cirrus clouds and dry air
near the surface should limit fog potential overnight.
However...cannot rule out MVFR fog developing at fog prone ags and ogb.
Have included tempo group to cover for now and will update as
Extended aviation outlook...restrictions re-enter the forecasts
beginning late Friday night as a Gulf Coast storm system approaches
the region. Additional restrictions possible with another system