Scientific Forecaster Discussion
fxus62 kcae 252150
Area forecast discussion
National Weather Service Columbia SC
550 PM EDT Tue Jul 25 2017
an upper level trough will remain over the eastern U.S., But it
will continue to be warm and humid across the area. This will
keep thunderstorms in the forecast for the next couple of days
with scattered afternoon and evening showers and thunderstorms.
A weak cool front will stall north of the area today, then
dissipated over the area on Wednesday. A stronger cold front
expected to affect the area over the weekend bring more
unsettled weather and cooler temperatures.
Near term /until 6 am Wednesday morning/...
mean upper troughiness extending from New England SW to the Gulf
Coast. Upper disturbance over west central Georgia moving slowly east,
with indications of a weaker disturbance currently near the north SC/NC
coast moving slowly southeast. Atmospheric moisture gradient over our
region, with precipitable water values 1.4 inches across our
northern forecast area (fa) to 2 inches just south of the forecast area. Weak
surface trough appears to be stretched across the central fa, with
another surface boundary farther north over NC. Latest high
resolution models indicate best chance of convection later this
afternoon and evening will be across the southern portions of
the csra and midlands, where better moisture exists and ahead of
the approaching upper disturbance. Coverage elsewhere may be
limited by less moisture and some weak negative vorticity advection. Model forecast
soundings for cae indicate fairly high level of free convection height/convect temp.
Other isolated activity possible elsewhere, more likely near the
weak surface trough or other boundaries. Latest satellite
imagery indicating some enhanced cumulus, but no echoes
appearing on radar yet. Think chance pops southern csra/S
midlands in order, with slight chance elsewhere through this
Upper disturbance will continue to track east towards the
csra and our southern forecast area overnight, while surface boundary to
our north slips south into the forecast area. These factors may provide
some continued possibility of showers or possibly an isolated
thunderstorm late tonight. Models consensus indicates slight
chance pops in order.
Short term /6 am Wednesday morning through Wednesday night/...
a weak upper low along the Alabama/Georgia border this afternoon will
slowly drift east and eventually move off the southeast coast
Wednesday night. Additionally, a weak cold front will move into
the area from the north and dissipate. Models indicate some
surface convergence where these two feature meet...in the
vicinity of the midlands and Pee Dee regions. This should
provide enough forcing with daytime heating, temperatures
around 90 for some afternoon showers/thunderstorms. Once again
some of the storms could produce locally heavy rainfall as precipitable water
values are around 2.0 inches. Overnight lows will continue in
the low to mid 70s.
Long term /Thursday through Tuesday/...
a slightly drier airmass is expected to advect into the area on
Thursday as the models indicate ridge across the central/western
U.S. Tries to build a bit farther to the east into the
southeast. Have continued with slight pops across the area for
Thursday. More changes as the mid/upper level pattern begins to
change during the remainder of the long term period. Models
indicate a vigorous S/W will dive southeast from Canada and to
the mid Atlantic coast by Saturday/Sat night. Additional
weakness will develop along the East Coast into next week. The
cold front associated with this system will move across the
region Friday night/early Saturday. This will increase the
chance for showers and thunderstorms during the
afternoon/evening hours. Will also need to monitor for the
potential for severe weather with the cold front late Friday
afternoon into early Saturday. The front will likely become
stationary across Georgia/SC for much of the extended period.
Temperatures will warm ahead of the front on Friday into the
low/mid 90s...then cool down slightly for the remainder of the
period into the mid/upper 80s.
Aviation /22z Tuesday through Sunday/...
VFR expected this afternoon and early evening outside of any
showers or thunderstorms. Scattered storms developing over
portions of the southern csra and central midlands late this
afternoon. Drier air over northern and central SC should help limit
areal coverage of convection somewhat in the midlands, but given
latest surface obs and radar loop, will mention thunder at
cae/cub until around 00z. Have also mentioned thunder at
ags/dnl/ogb, where better moisture exists along with an
approaching upper disturbance. Included a thunderstorms in the vicinity mention until
around 02z at those sites.
The upper disturbance will continue to track east towards our
forecast area overnight and Wednesday, while a surface boundary over
NC back doors down into our forecast area. This will provide a slight chance of
showers, possibly an isolated thunderstorm, late tonight into
Wednesday morning, along with a light easterly low level flow
developing which may enhance low level moisture and provide a
chance for lower cigs.
Increased chance of showers and thunderstorms Wednesday afternoon,
mainly after 18z.
Extended aviation outlook...mainly afternoon/evening thunderstorms,
along with late night/early morning fog/stratus.