Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus62 kcae 181836 
afdcae

Area forecast discussion
National Weather Service Columbia SC
136 PM EST Sat Nov 18 2017

Synopsis...
high pressure ridging into the area from the western Atlantic
will move out to sea this evening. A cold front will move
rapidly across the region tonight with scattered showers and
breezy conditions. A dry and cooler air mass will build over the
area Sunday and Monday. Moisture will return mid to late week
as the weak low pressure develops over the Gulf of Mexico.

&&

Near term /through tonight/...
surface high pressure off the southeast coast will continue moving
out to sea this evening as a cold front approaches from the west.
Given southerly winds and warm advection...will see afternoon highs
in the upper 60s to mid 70s under partly cloudy skies.

Little change in the forecast for tonight. A positively tilted upper
trough over the Mississippi Valley this evening will move across the
region overnight and into Sunday. Short wave trough appears to
weaken as it crosses the area with stronger dynamics to our north.
The trough will push a cold front through the area late tonight.
Front appears to move through the area between 06z and 10z with
scattered showers. Of concern is the very strong low level shear
with 60 kts at 850 mb. Instability appears very limited however with
sref most unstable cape around 50 j/kg. Little support for
thunderstorms noted in NAM/GFS operational runs. Moisture appears to
be a limited factor as well with maximum precipitable water 1.5
inches. Highest pops in the Piedmont and north midlands where upper
level forcing may be stronger. Gusty winds expected overnight with
strong mixing and a lake Wind Advisory may be needed. The showers
are expected to clear the midlands and csra by 12z Sunday.
Temperatures should remain mild ahead of the front due to
mixing...with lows from the upper 40s west to the mid 50s east.

&&

Short term /Sunday through Monday/...
on Sunday expect cold advection and clear skies. Breezy
conditions thru the morning, with diminishing winds during the
afternoon as the pressure gradient relaxes. Daytime highs will
be mostly in the lower 60s with downslope flow offsetting cold
advection somewhat. Temperatures near freezing in some areas
Sunday night especially northern and central counties. Patchy
frost possible may be possible elsewhere late Sunday night.
Dry and cooler air mass over the area Monday with temperatures
ranging from around 60 north to the lower 60s south.

&&

Long term /Monday night through Saturday/...
the upper level pattern remains somewhat amplified later in the
week, but large model differences result in a lower than normal
confidence forecast. Latest GFS and Canadian models are leaning
toward some sort of low pressure development in the Gulf of
Mexico with a cut-off upper low over the Gulf states by Thursday.
Moisture appears to focus early along old frontal boundary
across Florida to the Georgia and Carolina coastline. Will keep
a small chance for rain mid to late week including Thanksgiving
although confidence remains low with large spread in guidance.
Leaning toward cooler than normal for Thanksgiving given the
pattern and possibility of rain. Overall, temperatures generally
near normal through mid-week, then below normal through
Saturday.

&&

Aviation /18z Saturday through Thursday/...
high confidence for VFR conditions through the evening.

Surface high pressure over the western Atlantic will continue moving
out to sea this evening as a cold front approaches from the west.
VFR for the rest of the afternoon with cloud bases 4kft to 5kft.
Southerly wind 10 to 15 knots with gust around 20 knots this
afternoon forecast to increase tonight as the pressure gradient
tightens ahead of the cold front. Have continues low level wind shear all taf sites
01z-12z. An approaching front will cross the taf sites in the 06z-
11z time-frame. Brief rain showers and associated restrictions
possible ahead of the front. By 12z the front will be east of the
area with rapidly clearing skies and northwest winds 10 to 15 knots.

Extended aviation outlook...increasing low level moisture may help
support late night/early morning IFR or MVFR conditions Monday night
through Wednesday.

&&

Cae watches/warnings/advisories...
Georgia...none.

National Weather Service Glossary of Abbreviations