Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
539 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 southeastern states. A cold
front and increasing moisture will bring increasing chances for
showers this weekend into early next week...along with a trend
towards cooler temperatures.
Near term /until 6 am Saturday morning/...
weak upper trough to remain across the region tonight. Forcing
expected to remain rather weak over the area this evening.
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 into the early evening.
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 /6 am Saturday morning 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 /22z Friday through Wednesday/...
expecting VFR conditions with scattered to broken cumulus. There remains a a
slight chance of showers/thunderstorms into the overnight hours.
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 as needed.
Extended aviation outlook...late night/morning fog/stratus
possible...with a chance of showers and possible thunderstorms.