Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Columbia SC
151 PM EDT Thursday Jul 2 2015
an upper level trough...weak surface boundaries...and plentiful
atmospheric moisture will remain in place...providing a good
chance of showers and thunderstorms and near normal temperatures
through the weekend.
Near term /through tonight/...
convergence into a weak surface trough should help support
thunderstorms. Expect greater coverage late this afternoon
associated with lift ahead of a middle-level shortwave trough plus
heating. The models also show increasing shear ahead of an 850 mb jet.
The NAM is most pronounced with this feature with 850 mb winds
increasing to 40 knots tonight. There is a possibility a Bow echo
will develop ahead of the jet. The Storm Prediction Center WRF and hrrr suggest a well
organized area of storms with Bow type features late this
afternoon and evening. Damaging wind may occur. The 850 mb jet may
help maintain showers and thunderstorms through much of tonight
although there is uncertainty because of the stabilizing effects
of previous convection. Precipitable water increasing to just over
2 inches indicates excessive rain is possible.
Cloudiness and mixing should help hold up temperatures tonight.
Used the warmer temperature guidance.
Short term /Friday through Saturday night/...
an upper level trough will remain over the east Continental U.S....with a
series of embedded short waves prognosticated to move through the region.
Weak Lee side surface trough will remain over the central
Carolinas Friday. A frontal boundary to our north appears will
slowly slip south to near our northern forecast area Sat. Models
maintain precipitable water values around 1.8 to 2 inches
Friday...and 1.6 to 1.8 inches Sat/sun. Chance to good chance probability of precipitation
seem reasonable. Most convective activity would appear to be
diurnally favored...though timing of short waves and presence of
surface boundaries could provide at least a slight chance at other
Latest visible satellite images indicates area of smoke that was
over our region yesterday has pushed well east of our forecast
area...mainly offshore the middle Atlantic coast. Satellite...metars
and pilot weather reports do not appear to indicate any significant smoke or haze
immediately upstream...but there is a large area over central Canada
south into the northern plains and upper Midwest. With an upper
trough over the east Continental U.S....there is some concern that additional
smoke could drift into our region. However...latest models
indicate short wave energy will shift from northern plains southeast into
the Midwest by Sat/sun...with trough axis staying just to our north
and northwest which appears to shift the upper flow over our region to
more west-southwest or SW. This would suggest smoke staying to our
north...but there is uncertainty on that. But for now...not enough
confidence to include haze mention for Friday or Sat.
Long term /Sunday through Wednesday/...
by Sunday...models begin to shift the main upper flow to our
north with weak southern stream upper troughiness remaining over
the southeast Continental U.S./Middle Atlantic...with some indications that an upper
low could cut off over the central Apps/middle Atlantic. At the
surface...weak frontal boundary appears will slip south into our
forecast area and stall through Monday...with sufficient atmospheric
moisture remaining over our forecast area. Chance to good chance probability of precipitation
continue to appear reasonable.
Some indications by middle week that the upper flow could become less
amplified and more zonal though the main upper flow still remains to
our north. This appears will allow the upper trough axis to shift
east some...with expectations of surface boundary becoming diffuse
and possibly of some slightly drier air entering Tuesday into Wednesday.
Too much uncertainty this far out for that kind of day to day
detail...but will tweak probability of precipitation down just a tad for Tue/Wed...but
still chance. Possibilities of another front approaching late Wednesday
Generally accepted a blend of latest HPC and MOS guidance through
Aviation /18z Thursday through Tuesday/...
convergence into a surface trough plus upper troughing will help
support a chance of thunderstorms through the taf period. Expect
greatest coverage late this afternoon and possibly through much of
tonight associated with an 500 mb shortwave trough and 850 mb jet.
Radar trends with convection well upstream and hrrr trends would
suggest the most likely thunderstorm timing late this afternoon
and evening. An area of well organized thunderstorms may develop
associated with the upper-level support and ahead of the low-
level jet. Damaging wind will be possible with these storms.
Showers and thunderstorms associated with the low-level jet may
occur during much of tonight although there is uncertainty because
of the stabilizing effects of previous convection.
Shear associated with the low-level jet may be close to meeting
the low level wind shear criteria late tonight.
Extended aviation outlook...there is a chance of restrictions
through the period in mainly afternoon and evening thunderstorms...
and periods of morning fog.