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171
FXUS62 KCAE 190045
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
745 PM EST Sat Jan 18 2025

.SYNOPSIS...
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Another round of showers is expected to move through the area
tonight as a complex low pressure system moves into the eastern
U.S. A strong cold front will move through the area by midday
Sunday with strong gusty winds in its wake through the
afternoon. Behind the front, very cold air will begin to spread
across the region. Well below normal temperatures are expected
next week as an anomalously deep trough and surface high pushes
an arctic air mass into the central and eastern US. On Tuesday,
a coastal low will likely increase precipitation chances with
wintry potential increasing, but some uncertainty remains.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Key Message(s):

- Another round of rain overnight.

Surface low pressure currently in southern Alabama with a
deepening upper level trough over the central US. Positive
vorticity advection over the area wil lead to increasing lift
which combined with the deeper moisture returning with PWATs
expected to rise to above an inch in the southern portion of the
forecast area. HiRes guidance supports precip amounts around a
quarter inch to near a half inch in the far southeastern portion
of the area. Remaining mild tonight with cloudiness and low
temperatures in the mid to upper 40s.
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&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Key Message(s):

- A strong cold front pushes through Sunday, bringing breezy
  conditions and much colder temps overnight.
- The coldest airmass so far this season will move in Monday with
  temperatures near 20 degrees below normal.
- A Cold Weather Advisory may be needed Monday night.

Sunday and Sunday night...The highly amplified upper trough from
the Upper Midwest south through the Mississippi Valley will be
be shifting into the eastern CONUS. A low pressure area will be
near the region in the morning but will be lifting to the
northeast. A few lingering showers possible in the morning but
once the strong cold front moves through around noon, expect
drier air to begin advecting into the area. Strong cold
advection will develop in the afternoon with strong mixing.
Westerly winds 15 to 25 mph with gusts to 30-35 mph are expected
as the pressure gradient tightens between the low off the Mid
Atlantic coast and a very strong ridge in the Midwest. Temps
maxing out near 60 degrees but colder air will be spreading in
during the late afternoon hours. Cold advection continues
through the overnight with temperatures falling into the 20s as
the arctic air mass over the Midwest builds east.

Monday and Monday night...The arctic air mass (1040 mb high
pressure situated to the north) will be building over the area.
This is indicated by the very low dew points, in the single
digits. EC EFI and NAEFS continues to show this airmass with a
characteristic "highly anomalous but likely not historic"
signal. Temperatures will struggle staying in the 30s across
much of the region with full insolation due to continued strong
cold advection. Note 850mb temperatures around -10C in the
afternoon. Wind chill temperatures are expected to fall into the
teens Monday night near the cold weather advisory criterion.
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.LONG TERM /TUESDAY THROUGH SATURDAY/...
Key Message(s):

- Multiple impactful hazards expected.

1) High confidence in the coldest air of the year Tues.-Thurs.
2) Confidence continues to increase for impactful winter weather
weather Tues. into Wed.

1) High confidence in coldest air of the year Tues.-Thurs.

Arctic high pressure is forecast to be over the Mid-Atlantic region
to begin the long term period, which will likely allow for the
coldest air of the season to continue settling into the region.
Expect this cold to remain in the area into Thursday. All signs
continue to show that a Cold Weather Advisory will need to be in
place for the mid week time period. The cold air looks to be
reinforced by a passing coastal low (more on that in next paragraph),
resulting in high confidence that the coldest air sticks around into
Thursday. Temperatures Tuesday through Thursday afternoon might
struggle to get out of the 30s, and there is moderate confidence
(~50%) that many areas won`t top the freezing mark on Wednesday.
With such a cold stretch expected, take the necessary measures to
stay warm, prevent water pipes from bursting, and limit time
outdoors.

2) Confidence continues to increase for impactful winter weather
weather Tues. into Wed.

Confidence of ingredients being in place for an impactful winter
weather system continue to increase as models are now coming into
better agreement with a coastal low forecast to move along the
Southeast coast. The aforementioned cold air is very likely to be in
place on Tuesday. A developing low in the Gulf of Mexico is forecast
to move eastward across Florida, then along the Southeast coast.
Latest 12z guidance continues to show winter precipitation, likely
snow, looks probable for our forecast area Tuesday afternoon into
the overnight hours. However, there is some disagreement in the
amount. For example, the Euro ensemble is showing 80-90% chance of
at least an inch of snow for areas south and east of the I-20
corridor, while the GEFS ensemble is only showing a 20-30% chance in
the same areas. The NBM and LREF ensembles are indicating about a
50% chance of at least an inch, which seems reasonable to me
given the forecast set up. With the arctic high remaining near
the area, some really dry air is likely to be in place, which
will need to be overcome for snow amounts over an inch. Because
of this dry air, there is likely going to be a sharp cutoff
between snow accumulation and little to no accumulation. Another
factor that looks to limit accumulation is the speed that the
system is forecast to move through. As of now, it`s looking like
a Tuesday afternoon into Tuesday night system and be out of the
area by Wednesday morning. Despite a quick moving system, a
point that also needs mentioning is that with the cold air in
place into Thursday, any snow that is able to fall/accumulate is
likely to hang around for a couple of days. So be prepared to
deal with travel impacts beyond the typical snowfall in this
area.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
Widespread restrictions expected for much of the period.

The first round of rain is exiting to the east of the area and
should keep the TAF sites clear for much of the afternoon.
Restrictions may ease for a few hours as a result, but guidance
remains in good agreement that deteriorating conditions will return
this evening through tonight. Scattered to numerous showers are
expected to return to the area from southwest to northeast after
19/00z, with both CIGS and VSBYS dropping as moisture increases
particularly in the lower levels. -SHRA then expected to continue
through daybreak Sunday, and perhaps for a few hours more, before
clearing out to the east. Have continued CIG restrictions until the
end of the valid TAF period, but they may start to east an hour or
two prior.

Winds will generally be light and variable or SLY today, generally
less than 12 kts. We should see a period of light and variable winds
around 19/00z, then a bit of strengthening from the S/SW after
19/06z as a surface low tracks across the area. Speeds increase
Sunday morning after sunrise to 10-15 kts and continue veering W and
eventually NW by Sunday afternoon, becoming quite breezy with gusts
of 25-30 kts.

.EXTENDED AVIATION OUTLOOK...Expecting ceiling restrictions to
continue into Sunday morning. Cold front is forecast to pass
through the area by Sunday afternoon, which should improve
conditions. Gusty winds are expected with this cold front. No
restrictions are expected Monday, but could return on Tuesday with
the next weather system.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
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SC...None.
GA...None.
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&&

$$