Scientific Forecaster Discussion
fxus62 kcae 111149
Area forecast discussion
National Weather Service Columbia SC
649 am EST sun Dec 11 2016
high pressure over the area will shift off the coast tonight allowing
temperatures to begin to moderate Monday. Rain chances will
increase Tuesday and Wednesday as a cold front moves into the
area. A cooler air mass will return late in the week.
Near term /until 6 PM this evening/...
upper level flow today remains mainly zonal. Surface high
pressure extending into the area from the mid Atlantic region. Air
mass dry at the moment. However...satellite at 08z indicating low
clouds over southeast Georgia advecting north along the Savannah
River...associated with weak coastal trough and increasing
isentropic lift. Models in fair agreement with low-level
cloud...below 8000 ft spreading across the area during the day.
Appears to be a weak cold air damming situation...with
considerable low clouds by this afternoon...weak east-northeast
flow and moderately strong but shallow isentropic lift. So favor
cooler side of temperature guidance...with highs mainly in the mid
40s to mid 50s but limited precipitation. May be areas of drizzle
during the day.
Short term /6 PM this evening through Tuesday/...
models continue to have large spread in the pop guidance...highest
pops during the period appear to be on Tuesday.
Continued shallow moisture overnight with weak to moderate
isentropic lift. Considerable cloudiness and patchy drizzle/slight
chance light rain. Upper level flow backing as trough moves across
the Great Lakes region. The surface ridge will move offshore and
surface winds should come around to southwest by Monday morning.
This will result in moderating temperatures and continued increase
low level moisture. Limited forcing for showers during the day
although front should be approaching from the upstate by early
afternoon. So chance pops west and lower pops east. Front may be
nearly stationary across the southern County Warning Area or central Georgia by
Tuesday morning. The front appears to move north as a warm front. Models
suggest weak surface wave may develop along front and move through
the area during the day Tuesday and numerous showers may move
through the area...especially southern and east midlands. European model (ecmwf)
probability of precipitation are near categorical but again considerable spread in the
ensemble guidance. Overall qpf appears light however with
precipitable water below 1.30 inches. Despite clouds and chance
rain...expect warm day Monday and seasonable Tuesday. Overnight
temperatures will be warmer than last few days.
Long term /Tuesday night through Saturday/...
scattered to numerous showers will likely linger through Wednesday
as the surface front is slow to push offshore and second weak
surface wave moves along front. Another front moving through
Wednesday night should result in clearing. The southeast U.S.
Will be in a fast moving northwest flow aloft during the latter
half of next week as a deep upper low Parks itself over the
northeast U.S. Temperatures will be well below normal Thursday and
Friday before moderating on Saturday as high pressure aloft over
the eastern Gulf of Mexico builds northward.
Aviation /12z Sunday through Thursday/...
VFR conditions through Sunday afternoon...then giving way to MVFR
Low clouds have begun developing across the region with bases
around 4 kft over the taf sites. Cigs will slowly lower through
the day as moisture thickens the clouds with MVFR cigs expected by
mid afternoon. Rain will arrive late in the afternoon into this
evening with additional moisture further lowering cigs to
IFR...possible LIFR...during the early morning hours. Have
remained with vcsh as confidence in rain coverage remains low.
Winds will be east to northeast 6 knots or less through the
period...with a southerly low level jet producing wind shear from
12/00z through the end of the period.
Extended aviation outlook...IFR and/or MVFR ceilings and
visibilities possible Monday through early Wednesday as a frontal
boundary stalls over the region.