Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Columbia SC
1109 am EST Thursday Nov 26 2015
a pressure ridge will extend through the forecast area through
Saturday. Moderating temperatures will occur. A frontal system
will be just northwest of the area Sunday and Monday.
Near term /until 6 PM this evening/...
morning analysis indicated an upper level ridge axis shifting over
the region while surface high pressure remained in place centered
over the middle-Atlantic into the Carolinas. Visible imagery showing
mostly sunny skies across the forecast area except for a few
patches of clouds near the csra resulting from the easterly low
level onshore flow. Model guidance has been too bullish for clouds
and continues to be today so have backed off the clouds in the
grids a bit...especially across the northern half of the forecast
area. Additional sun has allowed temperatures to quickly rise into
the 60s and nearing forecast highs late this morning so have
bumped up temperatures a few degrees as well. No chance of rain as the
airmass remains dry with precipitable water values around 0.6 inches and general
subsidence over the area.
Short term /6 PM this evening through Saturday/...
the models maintain surface ridging in the forecast area through
Saturday. Aloft...the upper ridging flattens which should allow
more high cloudiness. There also appears to be enough low-level
moisture for stratus and fog during the early morning hours. We
used the guidance consensus for the temperature forecast.
Long term /Saturday night through Wednesday/...
the GFS and European model (ecmwf) were consistent keeping the bulk of the moisture
associated with a front northwest of the forecast area though
Monday...but an onshore flow and possible series of middle-level shortwave
troughs in a flat southern stream may help support showers. A
front Tuesday or Wednesday and possible low pressure developing
near the Gulf Coast supports a chance of showers Tuesday and
Wednesday. The GFS and European model (ecmwf) were in poor agreement with the
timing late in the period. The GFS and European model (ecmwf) MOS probability of precipitation were 20
percent or less through Sunday...and 30 to 70 percent Monday
through Wednesday. The MOS had temperatures above normal through
Aviation /16z Thursday through Monday/...
surface high pressure remains centered over the region with a
building upper ridge aloft. Low level flow at 925mb and 850mb is
from the east off the ocean and expect a gradual increase in low
level moisture across the region. VFR conditions expected through
06z or so with a relatively dry airmass beneath upper level
subsidence. Northeasterly surface winds expected to prevail today
around 5 to 10 knots then subsiding a bit overnight.
Model guidance is suggesting restrictions due to fog at all
terminals late tonight...however latest hi-res models do not
indicate this so confidence is low.
Extended aviation outlook...an onshore flow will bring increasing
low level moisture and the chance for ceiling/visibility restrictions during
the late night and early morning hours over the weekend.