Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 131757

Area Forecast Discussion
National Weather Service Columbia SC
157 PM EDT Sun Aug 13 2017

A moist atmosphere will remain over the region through much of
the forecast period. A dissipating frontal boundary remains
over the area. A surface low developing in the lower Mississippi
Valley will move along the front and into the area on Monday.
This will bring unsettled weather and chances for showers and
thunderstorms through mid next week. Expect near or slightly
below normal max temps. An upper ridge will build over the
region late in the week with warming temperatures.

Tropical Depression 8 has been designated by NHC well east of
the Bahamas. Official forecast track keeps the feature well
offshore with no impact to our forecast area.


The region is between weak upper troughiness over the eastern
U.S. and an east to west elongated upper ridge axis to the
south. A surface front remains stalled across the Midlands, and
has been the focus for developing showers and thunderstorms this
afternoon. It does not appear there is much in the way of an
upper trigger, but sufficient moisture combined with diurnal
heating and low level convergence along the boundary has resulted
in scattered showers and thunderstorms. Greatest activity is
currently from just south of Columbia northeastward into
Lancaster and Chesterfield counties. Storms are moving slowly
eastward. While widespread severe weather is not likely, heavy
rain is very possible with PWs above 2 inches. Gusty outflow
winds up to 40 mph are also possible. High resolution models
still indicate activity developing along a sea breeze as well,
impacting the southern counties. By late afternoon and evening,
it is possible that outflow boundaries from these two areas of
convection could lead to additional development elsewhere.
Activity will diminish after sunset, but isolated showers could
continue through late evening.

Maximum temperatures are in the lower to mid 90s today with heat
index values around 105. It will remain warm and humid overnight
with lows in the mid 70s. Patchy fog and stratus is likely by
Monday morning.


Weak surface front will remain stalled out over portions of the cwa
through the period. High Pwat values will also be across much
of the area, with higher amounts over 2 inches across the east.
Models still indicating a few weak shortwaves moving through the
flow aloft. Still expecting the development of scattered
showers and thunderstorms by late morning, lasting into the
early evening each day. Activity becomes more isolated during
the overnight hours. Biggest issue with these showers and storms
will continue to be the threat for brief heavy rainfall,
especially with the training storms and the high moisture
content in the air. WPC keeps eastern portions of the cwa
outlooked in a marginal risk of excessive rainfall. Conditions
will remain hot and sticky each day, with afternoon high
temperatures around 90 and overnight lows in the 70s.


Both the GFS and ECMWF in general agreement with the main upper
pattern across the southeast through the period. Upper pattern
does flatten out some through the longer term period, with some
weak ridging possible Thursday and Friday, then a weak upper
trough/weakness develops in the ridge into the weekend. Models
keeping general diurnal showers/storms in the forecast each day.
Temperatures will be on the increase, with readings rising into
the middle 90s each afternoon. With the expected moisture and
high rh values, heat index values will range from 100 to 105
each afternoon.


Main concern will be TSRA potential this afternoon and evening.
A surface front is stalled across the Midlands. It does not
appear there will be much in the way of an upper trigger today,
but sufficient moisture combined with diurnal heating and low
level convergence along the boundary has resulted in scattered
showers and thunderstorms. Storms are developing along the
boundary that stretches across Augusta and Columbia. IFR
conditions are possible in heavy rain. Wind gusts to 30 kts are
also possible. Additional activity should develop along the sea
breeze to the southeast, and affect OGB. Storms will taper off
after sunset. Patchy fog and status and associated restrictions
can be expected Monday morning.

EXTENDED AVIATION OUTLOOK...A stalled frontal boundary will
linger during much of the period. Widespread restrictions are
likely especially due to stratus and fog during the late nights
and mornings. There will be scattered to numerous showers and
thunderstorms especially during the afternoons and evenings.




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