Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
616 PM EDT Friday Aug 28 2015
a frontal boundary will remain stalled near the coast through
tonight...with dry surface high pressure remaining anchored over
the western and central Carolinas. Increasing atmospheric
moisture will drift slowly north into mainly southern and western
portions of our region late Saturday...and into remaining areas
Sunday. Tropical cyclone Erika is expected to approach southern
Florida Sunday night. Refer to the latest advisory on Erika
issued by the National Hurricane Center.
Near term /through Saturday/...
weak high pressure will remain over the southeast for the evening
and overnight hours. A weak frontal boundary will remain stalled
off the SC coast. As a result...a northeasterly/easterly flow will
persist over the forecast area. Latest radar loop showing a few
showers mainly along the coast and across central/southern Georgia. Slight
chance probability of precipitation mainly southern forecast area still seems appropriate
for the early evening hours.
Overnight...mainly dry conditions under partly cloudy skies.
Overnight lows ranging from the middle 60s north to around 70
Short term /Saturday night through Sunday night/...
mean upper trough to our west with upper ridge remaining centered
to our east and southeast. Shortwave energy moving east into the Midwest
Sat/sun will allow upper energy and moisture to slowly shift
north from the Gulf into our region. With the exception of the
NAM...models continue to trend slower with moisture return...and
mainly relegate it to the S and west forecast area Saturday...as surface high
pressure and drier air remains entrenched over the western and
central Carolinas. Think slight chance probability of precipitation by afternoon for the
short wave forecast area look OK Saturday. Moisture expected to continue trending
slowly north Saturday night into Sunday...with indications of weak
surface high pressure and drier air still trying to hang tough
over the western Carolinas. Models indicate a pop gradient over
our forecast area Sunday with lower probability of precipitation north/higher probability of precipitation south.
Long term /Monday through Friday/...
upper trough to remain to our west with upper ridge to our east.
Main concern will continue to be status and track of tropical
cyclone Erika. Official forecasts bring the system into S Florida
by late sun...and northward into North Florida/S Georgia vicinity by Wednesday. Even
without the cyclone in play...it appears sufficient atmospheric
moisture would provide premise for scattered diurnal convection
over our forecast area anyway. Due to uncertainties regarding possible
impact of Erika on our region...will continue to maintain ongoing
forecast of chance probability of precipitation...trended a little higher to the south.
Generally blended latest guidance with ongoing forecast.
Aviation /22z Friday through Wednesday/...
lingering low-level moisture and nocturnal cooling may lead to
stratus and fog during the early morning hours. The NAM MOS
indicated MVFR or IFR conditions 06z to 15z. The GFS MOS plus sref
and hrrr guidance generally maintained VFR conditions. We leaned
toward the more optimistic guidance based on upper moisture
streaming into the area limiting net radiational cooling and
surface high pressure to the north pushing dry air toward the
area. An increase in moisture and heating may help support
thunderstorms Saturday afternoon but expect scattered coverage
with the chance too low to include in the terminal forecasts at
Extended aviation outlook...restrictions possible in mainly early
morning fog and stratus plus afternoon and evening scattered