Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
147 PM EDT Friday Sep 4 2015
an upper-level ridge will remain to our south and west...while an
upper-level low develops over the southeast. A cold front and
increasing moisture will bring increasing chances for showers this
weekend into early next week...along with a trend towards cooler
Near term /through tonight/...
weak upper trough to remain across the region through tonight.
Forcing expected to remain rather weak over the are through this
afternoon. Weak surface boundaries...along with sea-
breeze...should be the only focus areas for any convection. Precipitable water
values still between 1.6-1.8 inches...so marginal moisture
available for storms to form. Expect generally isolated to
scattered diurnal showers and thunderstorms across much of the
region late this afternoon and into the early evening.
Temperatures this afternoon should be able to climb back above
normal across majority of the County Warning Area...mainly due to plenty of
sunshine. Forecast highs in the middle 90s looking on track.
Later tonight the models begin to indicate additional shower
activity developing and moving slowly southward along a slow moving
back door front. Expect to see some showers continue to develop and
move across the forecast area from north to south during the
overnight hours. Confidence in coverage is rather low...but feel
that slight chance to chance probability of precipitation should suffice. Overnight lows
should be limited by some additional cloud cover...with lows in the
lower to middle 70s expected.
Short term /Saturday through Saturday night/...
the backdoor cold front will continue to slowly shift southward
through the forecast area on Saturday providing a focus for
convection. Moisture likely to be pooling along the boundary with
precipitable water values 1.8 to near 2 inches and shortwave energy associated
with a possible weak developing closed upper low will warrant
chance probability of precipitation...especially in the csra and western midlands.
Abundant clouds and precipitation will limit the amount of
insolation and result in cooler...near normal maximum temperatures in
the middle to upper 80s. Scattered showers likely to linger
across the southern part of the forecast area into Saturday night
while slightly drier air builds in from the north. Overnight
lows Saturday night in the upper 60s to around 70.
Long term /Sunday through Friday/...
relatively active weather expected early in the extended period
with a weak upper low over the southeast which dissipates by
midweek. Another upper trough over the Great Plains will move
towards the East Coast late in the week with an associated frontal
boundary approaching the Tennessee Valley by Friday. Persistent easterly
flow off the Atlantic Sunday through Tuesday will provide
sufficient moisture along with weak vorticity associated with the
upper trough to warrant at least diurnal scattered showers and
thunderstorms. Probability of precipitation increase to high chance by Friday as the
frontal boundary moves closer to the forecast area. Temperatures
during this period should be near to slightly above normal with
highs in the upper 80s to around 90...and overnight lows generally
Aviation /17z Friday through Tuesday/...
expecting VFR conditions with scattered to broken cumulus. There remains a a
slight chance of showers/thunderstorms through the afternoon and
into the overnight hours. With radar already showing some shower
development across the south and eastern County Warning Area...have elected to
place vcsh in ags/dnl/ogb for a short period. Will then update all
taf sites as showers continue to develop and move across the County Warning Area
Extended aviation outlook...late night/morning fog/stratus
possible...with a chance of showers and possible thunderstorms.