Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area Forecast Discussion
National Weather Service Columbia SC
205 PM EDT MON SEP 26 2016

A cold front will slowly cross the area late Tuesday into
Wednesday. The air mass behind this system will bring dry weather
and more seasonable temperatures for the latter half of the week
into the weekend.


Weak backdoor front has stalled over the Pee Dee region just south
of the NC/SC border in the Pee Dee region. Weak upper ridge
shifting off the coast this afternoon a digging upper
trough/closed low moves into the Great Lakes region. This will
drive a cold front into the mountains this afternoon and slowing
its push toward the forecast area overnight. A weak surface low
off the northern FL coast was pulling low-level moisture from the
Atlantic into the region. Latest radar loop showing scattered
showers with a few thunderstorms moving into the Lowcountry and
southern Midlands. Expect scattered precipitation to continue over
much of the area this afternoon into tonight. Latest SPC HRRR
indicating that precipitation will slowly diminish by late

Temperatures this afternoon will again be well above normal in
the mid to upper 80s with overnight lows tonight in the upper 60s.


Tuesday looks to provide the best chance for precipitation across
the forecast area as precipitable water values maximize just ahead
of the cold front with values approaching 1.9 inches with upper
height falls and moderate instability forecast. The cold front will
slowly push into the forecast area Tuesday afternoon and Tuesday
night as the 500mb flow backs more southerly, nearly parallel to the
front as the upper trough amplifies.  The front eventually pushes
through on Wednesday as the upper level closed low drops southward
into the Ohio Valley. Much drier air will then filter into the area
from the northwest with precipitable water values falling below an
inch by Wednesday evening. 

Will carry high chance pops across the forecast area on Tuesday into
Tuesday evening with diminishing pops late Tuesday night as the
atmosphere stabilizes. Will continue higher pops on Wednesday across
the eastern half of the forecast area with lowering pops through the
afternoon from west to east as drier air filters into the region.

Temperatures will remain above normal with highs Tuesday in the mid
to upper 80s and slightly cooler on Wednesday in the lower to mid
80s.  Overnight lows Tuesday night will remain mild in the mid to
upper 60s while temperatures will drop a couple of categories for
Wednesday night with min temperatures in the upper 50s to lower 60s.


Medium range models remain in reasonable agreement. There is
agreement that the closed low will completely cut off from the
westerlies near OH/KY THU/FRI and then slowly lift northward into the
Great Lakes region over the weekend. At the surface, weak low
pressure will linger to our north across the Mid-Atlantic and Ohio
Valley with cooler and drier continental high pressure ridging into
the area from the west. Models indicate precipitable water values
less than one inch. Despite very cold 500mb temperatures around -12C
to -16C over the area Thu/Fri with steep mid level lapse rates, the
lack of moisture should limit or preclude precipitation associated
with the upper low, although expect some cloud cover.

Seasonable temperatures are foreseen with Highs will be in the mid
70s to lower 80s and overnight lows will be in the mid to upper 50s.


Back door front appears to have pushed south into the Pee Dee and
stalled. Cigs VFR this afternoon.

Back door front will slowly become more diffuse into tonight as
another cold front approaches from the west during the overnight
hours. SPC HRRR indicating that the best chance for precipitation
this afternoon into tonight will be mainly over the southern
Midlands and lower CSRA, so have mentioned VCSH at OGB/AGS/DNL late
this afternoon into tonight, although cannot rule out a brief shower
at CAE/CUB during this time as well. The HRRR indicates the
precipitation diminishing by late evening. Other convective activity
along or ahead of the approaching front late today/this evening
appears will remain north of the terminals. Moist low levels
suggests deteriorating conditions on tap again late tonight,
so have mentioned the possibility of IFR conditions developing at
all terminals early Tuesday morning, becoming VFR by late morning.
Some convection may develop after 14Z Tuesday, but not enough
confidence to mention at any of the TAF sites at this time. 

EXTENDED AVIATION OUTLOOK...Chance of showers and possible
thunderstorms, with associated restrictions Tuesday into





National Weather Service Glossary of Abbreviations