Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
1032 am EDT Thursday Oct 2 2014
the pressure ridge extending through the forecast area will shift
just off the coast this afternoon. An approaching cold front will
move through the area late 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
Near term /through tonight/...
the surface ridge extending through the forecast area will shift
just off the coast this afternoon. The pressure gradient will
remain weak with the ridge near the area but a south to southeast
wind will become more dominate as the ridge moves eastward this
afternoon. The NAM and GFS indicate building upper-level ridging
today. It will be another warm day and expect highs in the upper
80s to around 90. Record highs for today/S date are 93 and 95 at
ags and cae...respectively. The ridge should keep the deeper
moisture west of the forecast area through tonight. Used the
guidance consensus for the temperature forecast.
Short term /Friday through Saturday/...
the NAM and GFS show the cold front approaching Friday with frontal
passage late Friday night or early Saturday morning. The GFS is
about 6 hours faster with the frontal timing. However...both models
indicate deepest moisture in the forecast area ahead of the front
late Friday afternoon into the evening associated with a middle-level
shortwave trough. We forecasted the highest probability of precipitation during that period.
The models display 850 mb winds 30 to 35 knots. This shear supports
organized thunderstorms and damaging wind gusts could possibly
occur but the chance appears low at this time because of expected
weak instability. The NAM displays surface-based Li/S -2 to -4.
The weak instability appears reasonable because the models are
consistent showing much of the upper-level lift staying well north
of the forecast area. Drying behind the front should dominate
Saturday. The NAM and GFS MOS indicate breezy conditions Saturday
with winds 15 to 20 miles per hour. Used the warmer temperature guidance just
ahead of the front Friday. Mixing and cloudiness associated with
the front supported the warmer temperature guidance Friday night.
Also used the warmer temperature guidance Saturday. MOS is usually
too cool when there is an early morning frontal passage and we get
off to a relatively warm start with downslope wind.
Long term /Saturday night through Wednesday/...
the dry air mass behind the cold front will likely dominate through
much of the medium-range period. Moisture mainly associated with a
middle-level shortwave trough appears limited Tuesday. The GFS and
European model (ecmwf) MOS have probability of precipitation 20 to 30 percent Tuesday...and less than 20
percent during the rest of the period. The coolest temperatures
should be Saturday night and Sunday night with the pressure ridge
near the area. The GFS and European model (ecmwf) MOS support lows mainly in the
middle and upper 40s those nights.
Aviation /15z Thursday through Monday/...
high confidence in VFR conditions through 03/00z. Restrictions
possible in early morning fog.
High pressure will be over the area today with dry weather and
mostly sunny skies expected. Winds will be mainly from the south
by the afternoon with scattered clouds 4 kft to 6 kft. MVFR/IFR
fog possible across the forecast area early Friday morning...but
not enough confidence to mention in the tafs at this time.
Extended aviation outlook...restrictions possible in showers and
thunderstorms Friday afternoon and Friday night as a cold front
crosses the region. Post frontal gusty winds could develop Saturday.