Scientific Forecaster Discussion
area forecast discussion
National Weather Service Columbia SC
749 PM EDT Monday Sep 22 2014
high pressure will build south from the middle Atlantic region and
remain to the north of the area through the week resulting in
easterly low level flow. The moist low level flow will result
in unsettled weather with considerable clouds and a chance of rain.
Near term /until 6 am Tuesday morning/...
front continues slowly moving through the forecast area with
current position from the central SC coast into southern Georgia.
Showers and isolated thunderstorms developed during the middle
afternoon over the eastern midlands through the inland coastal
areas and continue moving northeastward across the area. With the
front slowly pushing eastward expect the showers to persist over
the next couple of hours across the eastern midlands with chances
rapidly lowering westward as drier air filters into the area.
Overnight the front will stall along the coast as the upper level
trough transforms into a cut off low over the area. This will keep
light easterly flow over the region with cloudy skies and chance
probability of precipitation over the eastern midlands with partly cloudy skies and dry
conditions expected for the western midlands. Overnight lows will
range from the upper 50s over the western midlands to the lower
60s in the eastern midlands.
Short term /6 am Tuesday morning through Tuesday night/...
NAM...GFS and European model (ecmwf) all dig a vigorous shortwave over the
southeast tonight which cuts off and remains over the Carolinas
and Georgia through Tuesday night. At the surface...high pressure
builds to the north and brings a long fetch of easterly flow off
the Atlantic over the southeast. For now have a northwest/southeast gradient in
the probability of precipitation with highest values over the southeast County Warning Area in the 20-30 percent range.
Lower probability of precipitation to the northwest in the 10-20 percent range. Limiting factor for
precipitation is drier air aloft. A blend of the guidance looks good for
Long term /Wednesday through Monday/...
surface high pressure generally remains parked to the north through
the long range. Aloft the westerlies lift well to the north and a
weakness in the upper flow remains over the southeast US. Low level flow
with an easterly component will continue. Result is probability of precipitation above
climatology through the period generally in the 20-30 percent
range. With increased clouds...maximum temperatures will be below climatology
and min temperatures slightly above.
Aviation /00z Tuesday through Saturday/...
stalled frontal boundary south of the taf sites. Easterly flow will
continue to spread moisture into the area. VFR conditions early this
evening are expected to deteriorate to MVFR ceilings/visibilities at
ags/dnl/ogb tonight. Rain showers will cross the taf sites from time
to time through around midnight.
MVFR ceilings expected during the day Tuesday as an upper level area low
pressure develops over the area...producing instability...lift and
scattered showers. Winds from the northeast 5 to 10 knots...
increasing to 10 to 15 knots after 12z.
Extended aviation outlook...restrictions possible during the period
associated with moist easterly low level flow.