Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
648 PM EDT Sat Jul 30 2016
upper level ridge continues to slide into the Atlantic Basin as
the upper trough digs across the MS River Valley into the Ohio
River valley. A series of short waves rotating through the base of
the trough will result in increasing chances of thunderstorms over
the next several days.
Near term /until 6 am Sunday morning/...
a southwest flow will prevail aloft, between strong ridging over
the western Atlantic and a broad upper trough over the western
Great Lakes region and Mississippi Valley. Meanwhile, a weak
trough of low pressure will remain in place at the surface.
A series of weak short wave disturbance aloft, combined with
moderate instability and a fairly moist atmosphere (with
precipitable water values up around 2 inches) has supported a
couple bands of convection across the area. The first is shifting
out of the area into the Pee Dee, while the second is moving
across the csra. Have made some adjustments to the pop forecast,
but for the most part will maintain scattered showers and
thunderstorms in the forecast through the evening hours. While
most of the convection should dissipate after midnight, will hold
on to a slight chance of showers and thunderstorms over the
eastern midlands, supported by some of the high resolution
Temperatures tonight should fall to lows in the mid 70s across
much of the area.
Short term /6 am Sunday morning through Monday night/...
an upper level trough will continue to shift eastward through
Monday as a weak surface boundary approaches from the north.
Moderate instability and multiple disturbances moving through the
upper trough support and increasing chance for thunderstorms.
Scattered convection is expected Sunday afternoon in a moist,
moderately unstable airmass. Lingering upper level ridging and
lack of a strong forcing mechanism at the surface should keep any
convection scattered. Although mid-level temperatures will be
slightly cooler than previous days, the threat for severe storms
is low. A skinny area of positive buoyancy in the forecast
soundings suggest pulse type thunderstorms with weak updrafts.
Models do show an upper level shortwave moving through the area
Sunday afternoon/evening which may help promote development. The
GFS indicates the potential for a sea-breeze to move inland
triggering additional convection Sunday evening. The shortwave
may allow for storms to linger overnight. Highs will be in the mid
to upper 90s with lows in to mid 70s.
Monday, as the upper trough amplifies and moves further east, the
associated surface boundary will enter the region. Convergence
ahead of the boundary will allow for thunderstorms to develop in
the forecast area. 500 mb temperatures around -8 degrees will be
more conducive for strong thunderstorms Monday afternoon. Given
the cooling mid-levels and a higher confidence in thunderstorm
coverage than previous days, highs should be in the low to mid-
90s. Cannot rule out the chance for thunderstorms into the night
with models indicating the possibility of multiple shortwaves
moving through the area.
Long term /Tuesday through Saturday/...
the upper level trough will remain over the eastern US in the
mid-term with ridging moving back over the area towards the end
of the period. A surface trough may linger in the region through
the week keeping the chance for thunderstorms in the forecast.
Temperatures are expected to remain a few degrees above normal
during the period with highs in the mid to upper 90s and lows in
the low to mid 70s.
Aviation /22z Saturday through Thursday/...
VFR conditions expected outside of scattered...mainly diurnal...
convection. Convection should diminish with sunset. Southwest
winds around 10 knots will also diminish with sunset.
Cannot completely rule out isolated convection overnight given
moist and unstable atmosphere. However...showers and
thunderstorms will once again increase in coverage Sunday
Extended aviation outlook...low potential for restrictions in
afternoon and evening convection each day.