Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
306 am EDT Thursday Aug 21 2014
drier air and a building upper ridge just to our west will reduce
thunderstorm chances through Friday...and lead to hotter high
temperatures. An approaching cold front and increasing moisture
will increase the thunderstorm chance over the weekend.
Near term /through today/...
considerable high level convective debris cloudiness will continue
to spread across the area early this morning. Clouds will thin out
after daybreak. Upper ridge centered over the lower Mississippi
Valley/Gulf Coast will be building into the region. Warm start to
the day along with 850mb warm advection/downslope flow will result
in temperatures approaching 100 degrees this afternoon.
Instability appears weaker than yesterday given warmer
temperatures aloft. Level of free convection remains high...convective temperatures high and
trigger lacking. Isolated afternoon thunderstorms expected. Dew
points mixing out into the middle 60s to low 70s this afternoon so
heat index likely maxing out around 105 degrees.
Short term /tonight through Saturday night/...
warming continues through Friday as upper ridge extends into the
area. Convection will likely remain isolated with trigger
lacking/weak instability. Expect temperatures slightly warmer than
Thursday most areas. Heat index expected to remain below 110
degrees. Back door cold front appears to move into the region late
Saturday or Saturday night from North Carolina...however latest
GFS suggests upper ridge will remain strong with long wave trough
off the North Carolina/Virginia coast. So temperatures may remain
quite high through Saturday with cooling delayed until Sunday as
front moves southwest of area. Scattered showers and thunderstorms
ahead of the front late Saturday or Saturday night although model
probability of precipitation suggest large Standard deviation/uncertainty.
Long term /Sunday through Wednesday/...
upper ridge to our west with upper trough and closed low to our
NE...providing a northwest flow aloft for our forecast area. Slightly cooler
temperatures Sunday as front moves slowly to the south of area.
Scattered showers. Large pop uncertainty due to timing issue with
frontal passage. Front may be slow to move south of the area
Sunday...especially in the csra. Front to push to our south early
next week...with surface and upper ridge over the eastern
Seaboard. So reduced probability of precipitation Monday through Wednesday as ridge builds
in from the northeast.
Aviation /07z Thursday through Monday/...
expect VFR conditions to dominate the period...with early morning
MVFR conditions at ags/ogb.
Cirrus from upstream convection continues to blanket the area and
will work to limit fog development. With the clouds expected
through much of the night have decreased the fog threat at
cae/cub/dnl to a tempo group while maintaining MVFR fog at
ags/ogb. Fog which develops will quickly erode with sunrise with
the remainder of the period VFR. Chances of diurnal convection
remain too low to include in tafs. Winds through the period will
be westerly at 5 knots or less.
Extended aviation outlook...MVFR or IFR conditions possible in late
night and early morning fog through the period. Isolated afternoon
and evening thunderstorms may also bring restrictions.