Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
255 am EDT Wednesday Oct 1 2014
a pressure ridge will remain near the forecast area through
Thursday. A cold front will move through the area Friday night and
early Saturday morning. Scattered to numerous showers and
thunderstorms will occur ahead of the front. The coolest
temperatures of the season so far will follow the front.
Near term /through tonight/...
today...nocturnal cooling with light wind and sufficient low-level
moisture will help cause areas of fog early this morning. A dense
fog advisory may be needed. Heating and mixing should dissipate
the fog before 1000 am. Surface high pressure ridging into the
forecast area with flat upper-level ridging will dominate. The
pressure gradient will be weak resulting in light winds. Satellite
trends support a mostly sunny day. The temperature guidance was
close with highs in the upper 80s.
Tonight...surface high pressure ridging into the forecast area
from the north with flat upper-level ridging will continue to
dominate. Sufficient low-level moisture with nocturnal cooling and
light wind should lead to areas of fog during the early morning
hours. The NAM and GFS MOS indicate fog. Used the guidance
consensus for the temperature forecast.
Short term /Thursday through Saturday/...
the NAM and GFS display the surface ridge shifting off the coast
Thursday with the approaching cold front moving through the area
late Friday night and early Saturday morning. The models indicate
the deepest moisture ahead of the front late Friday afternoon into
the evening. The NAM indicates surface-based Li/S -4 to -5 Friday
and expect there will be thunderstorms. There may be enough
instability and shear for a few severe thunderstorms especially if
stronger than expected warming occurs just ahead of the cold
front. The NAM and GFS indicate 850 mb winds of 25 to 30 knots.
Drying behind the cold front should dominate Saturday. The
temperature guidance was close Thursday and Thursday night. The
warmer guidance may be better just ahead of the cold front Friday.
Believe the warmer temperature guidance is also better Friday
night because of mixing associated with the front. The guidance
may be a little too cool with the temperature Saturday because of
a relatively warm start associated with the early morning frontal
passage and downslope wind behind the front.
Long term /Saturday night through Tuesday/...
the dry air mass behind the cold front will likely dominate
through the medium-range period. Upper troughing over the eastern
part of the nation should maintain below normal temperatures. The
GFS...ecwmf...and ekd MOS support the coolest temperatures
Saturday night and Sunday night with lows mainly in the middle 40s
to around 50. These temperatures will be the coolest so far this
Aviation /06z Wednesday through Sunday/...
VFR conditions at all sites early this morning except occasional
IFR/LIFR at ags/ogb. Still expect ideal radiational cooling
conditions with clear skies and calm wind overnight. Lingering
low-level moisture will allow fog to develop during the pre-dawn
hours. Most of the guidance is in agreement with fog
development...so confidence is moderate. IFR/MVFR visibilities
expected at ags/ogb...especially 06z-13z. Have also included MVFR
visibilities at cae/cub/dnl 09z-13z. VFR conditions will return to
all sites after 14z.
Extended aviation outlook...late night/early morning fog and low
clouds possible Thursday. Restrictions possible in showers and
thunderstorms Friday and Friday night as a cold front crosses the