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000 
FXUS62 KCAE 130321
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
1021 PM EST Tue Dec 12 2017

.SYNOPSIS...
High pressure and reinforcing cold air will be moving into the 
region this overnight through Wednesday. A dry front will cross
the area Thursday followed by high pressure Friday and 
Saturday. Unsettled weather will return early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Little changes needed late this evening as cold advection
continues across the region. Made some adjustments to hourly
temps to better reflect the trends, slightly warmer than
forecast in the Midlands but overall the forecast is on track. 

Lake wind advisory remains in effect through 4am Wednesday. 

Latest analysis reveals a deepening surface low moving 
northeastward along the New England coast with a cold front 
trailing well off the Carolina coast and across central 
Florida. A secondary trough with much drier air and dewpoints in
the low teens was noted across eastern NC into the Upstate of 
SC at 03z. 

Persistent northwesterly winds will continue to usher in colder
and drier air through the night as temperatures fall through 
the 30s by midnight as high pressure builds over the region. 
Overnight lows will be limited by the winds staying up in the 
boundary layer and preventing strong radiational cooling, but 
the cold advection is significant and expect min temperatures to
range from the mid/upper 20s in the northern Midlands to around
30 to lower 30s in the lower CSRA and southeastern Midlands.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Dry weather is expected Wednesday and Thursday. High pressure 
building across the area Wednesday will slip south by Wednesday 
night. A clipper system crossing the Ohio Valley to the Mid-Atlantic 
Coast Wednesday night into Thursday morning will push a weak 
and dry cold front into the region Thursday night. Temperatures 
at 850 mb will start out cold Wednesday morning...ranging from 
minus 8C north to minus 2C south...with some warming during the 
day as the thermal trough moves east. MOS guidance has been 
fairly consistent with afternoon highs in the mid 40s to lower 
50s on Wednesday... moderating to the mid 50s to lower 60s 
Thursday as the upper flow becomes zonal. 

We could see some increase in clouds Thursday night as Gulf moisture 
returns northward while low pressure digs into the mid MS Valley. 
Models continue to depict the moisture return as a split stream with 
much of the Gulf moisture remaining south of the area Thursday night 
with the northern stream only reaching the TN Valley and remaining 
north of the area. With the split stream and dry air to overcome, 
Thursday night still looks dry.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Models indicate an upper-level trough swinging through the 
forecast area Friday night with much of the moisture associated 
with the system maintaining a split flow around the area. Have 
remained with slight chance pops for Friday due to low 
confidence. Any rainfall will quickly exiting the area Friday 
night as low pressure near the coast lift northeast. Surface 
high pressure along with upper-level ridging moves into the 
area Saturday. 

On Sunday the high pressure will move away from the region as the 
next low pressure system develops over the Southern Plains 
region and ushers Gulf moisture northward. Models differ with 
timing and intensity of this system however agree on the chance 
for rain returning to the forecast area Sunday afternoon through
Monday or Tuesday. Temperatures through the long term will be 
below normal Friday and Saturday with near normal for Sunday 
through Tuesday.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Expect VFR conditions through the 24-hour TAF period. 

Wind will diminish tonight as the low to our northeast moves
farther away and the pressure gradient relaxes somewhat. Ridging
extending along the Gulf Coast will maintain a dry westerly
flow. The dry air mass and mixing should preclude fog. We
followed the GFS LAMP for the wind forecast.

EXTENDED AVIATION OUTLOOK...No significant impacts expected.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...Lake Wind Advisory until 4 AM EST Wednesday for GAZ040-063>065-
     077.
SC...Lake Wind Advisory until 4 AM EST Wednesday for SCZ015-016-018-

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