652
FXUS62 KCAE 191152
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
652 AM EST Sun Jan 19 2025

.SYNOPSIS...
A strong cold front will move through the area by midday 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 through the 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, but some uncertainty remains.

&&

.NEAR TERM /THROUGH TONIGHT/...
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.

Low pressure early this morning was located over southwest GA
with a warm front near the central Midlands. Radar at 08z is
showing light to moderate showers focused over the CSRA
northeast across the eastern Midlands. As the low lifts to the
northeast across the area this morning, expect scattered showers
to possibly spread into the central Midlands, but think highest
pops will be in the east and Pee Dee by 12z-15z as the warm
advection/isentropic lift shift northeast. The other issue is
the extensive low clouds and fog across the region. Will monitor
for possible dense fog advisory. The low will move to the
northeast of the area mid morning as the highly amplified upper
trough in the Plains moves east. The showers then diminish
across the area. The arctic cold front will move through the
region around midday and winds will shift to west and northwest
tonight. The tightening pressure gradient between the arctic
high in the Plains and the departing/deepening low near the
NC/VA coast this afternoon along with developing cold air
advection, will result in breezy conditions across the region
through the afternoon into the evening. Expect wind gusts 30
mph, may be a few gusts 35-40 mph late this afternoon with
strong downward vertical motion and 35 kts at 900 mb. Should mix
this down. Max temps a little tricky as we are starting out
relatively warm this morning in the 50s. Downslope flow may
delay cooling at least initially. Strong cold advection
continues overnight, but the winds will slowly relax toward
daybreak as the pressure gradient weakens. Models indicate 850mb
temps will be near -10C at CAE by morning. Minimum temps
tonight look like mid 20s across much of the area probably
dropping quickly near daybreak when winds relax given dew points
in the teens by then. Wind chill temps in the 20s most of the
night but may fall into the teens, close to cold weather
advisory by daybreak but should be a brief period.

&&

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

- Multiple impactful hazards expected.

1) High confidence in a long duration cold temperatures as the
coldest airmass since December 2022 pushes into the southeastern
US

2) Confidence continues to increase for impactful winter weather
weather Tues. night into early Wed. especially across the
southeastern Midlands

3) Multiple Cold Weather Advisories may be needed this week, as
overnight temperatures and/or wind chill values are expected to
fall into the 10F-15F range

Well, a cold and complex period of weather is anticipated in
the short term, with models continuing to hone in on the
potential for accumulating snow Tuesday night. Well-advertised,
arctic high pressure system is forecast to settle into the
eastern CONUS by 12z on Monday, with well below normal
temperatures forecast through the day. Given that cold advection
should continue through the day on Monday, highs are only
forecast to get into the mid to upper 30s for highs across the
forecast area. Winds are expected to still be in the 5-10 mph
range early Monday morning, which could yield wind chill values
that approach cold weather advisory criteria. We look to be just
warm enough to avoid that at this point but that may be
something to look at as more guidance comes in later today.
Temperatures should be very cold on Monday night as high
pressure continues to sink southward into the central US,
ridging eastward as it does so. Lows on Monday night are likely
to get down into the mid to upper teens across the forecast area
and a Cold Weather Advisory is likely going to be needed on
Tuesday morning. Temperatures should moderate on Tuesday but
only into the mid 30s as clouds will likely increase throughout
the day ahead of our next weather maker.

Then, we get into the complicated portion of this forecast. Our
feature of interest is well upstream right now, having just emerged
from the Pacific and into the upper air network across North
America. It is a shortwave that is on the very outer edge of the
deep upper level trough covering the bulk of the CONUS and is
forecast to dig into the desert southwest over the next 24 hours. As
it ejects from the desert southwest on Monday, it should begin to
interact with another northern stream disturbance over the northern
Plains and amplify the upper level pattern as it does so. The
resulting response would be widespread precipitation developing
within the right-entrance region of the upper level jet. This would
then overspread the forecast area on Tuesday night and early
Wednesday. The airmass that will be in place ahead of this is
forecast to be anomalously cold and dry, so the bulk of the
precipitation in the event on Tuesday evening and Tuesday night
should remain snow.

The forecast has been tricky for this event to say the least.
Guidance has been playing a game of shifts over the last few days,
first suppressing the system well off-shore then shifting it
northwestward. The latest trends have been towards a more suppressed
system again, owing to a slightly stronger dig of the initial
shortwave from western Canada southward into southern California
before it then begins to eject eastward. Guidance tends to have a
southeastward bias with coastal low events, so it is hard to peg
exactly where we will end up with this event. The bulk of guidance
is landing on an event where the highest QPF remains along and east
of I-95, but still delivers some accumulating snow to the forecast
area. But just to give an idea of what we`re working with here: the
00z NAM has widespread snow on Tuesday night across the
forecast area while the 00z GFS has little to no accumulating
snow across the area at all! Thats not to mention that the
northwestern edge of this shield of precip should have a very
sharp gradient in amounts - likely sharper than forecast - due
to how cold and dry the antecedent airmass will be.
Additionally, guidance tends to underestimate the strength of
the warm nose aloft in these setups, which could introduce some
mixed precip in the areas that do see widespread precipitation
(some guidance is explicitly showing this). All of this, in
addition to the models just struggling to get a really firm
handle on this over the past few days, casts some uncertainty on
this event overall.

Probabilistic guidance, along with the Canadian and ECMWF suites of
guidance, seem to split the difference quite well without
flip-flopping one way or another too quickly. NBM probabilities
of >2" of snow (Winter Storm Warning criteria locally) are
40-50% across the southeastern Midlands, and this aligns well
with where the aforementioned other guidance aligns the best
probabilities for warning criteria snowfall. We are still a bit
too early, as well as too uncertain about location & amounts, to
issue Winter Storm Watches for our area. But based on the
latest guidance and model trends, a good forecast seems to be
that our southeastern tier of counties (Burke GA to Clarendon
SC) has the greatest threat for impactful accumulating snowfall.
Total snowfall, based on latest guidance, could come in around
1"-2" in these locations, with a dusting up to 1" possible in
the rest of our forecast area. Again, it must be stressed that
we are still a couple of days from this event actually
unfolding. Details may change, and the models (given their
recent propensity for flip/flopping) may shift again. But
confidence is growing that our southeastern counties will be the
focus for this quick hitting winter weather event. Temperatures
will likely be cold again on Tuesday night, regardless of
wintry precipitation, with lows expected to be in the upper
teens and lower 20s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Key Message(s):

- Cold temperatures are expected to continue through Thursday

- Another weather maker is forecast to develop Thursday night
  and early Friday with precipitation possible

- Low confidence in the forecast overall other than temperatures
  remaining below normal

In general, cold conditions are expected through the period. Arctic
high pressure is expected to continue working eastward across the
CONUS, with highs and lows well below normal through the end of the
week. Cold weather advisories are possible Wednesday morning but
likely again on Thursday morning as near ideal radiational cooling
conditions look possible on Wednesday night. The record low on
January 23rd is 13F at CAE and 16F at AGS; both of those are in
jeopardy of falling especially if there is even marginal snow cover
across the forecast area. ECMWF EFI backs up this possibility
with high values along with a shift of tails near 2 across the
area. Please remember to drip you faucets this week as multiple
days in a row of high temps only slightly above freezing along
with lows below 20F may cause problems with pipes freezing.
Another weather maker is expected to develop on Thursday night
and Friday, but guidance is completely split with respect to how
that evolves. There may be a warm up over the weekend but there
is significant uncertainty in the evolution of the upper level
and surface pattern at that point in the forecast, so it is hard
to speculate on the forecast beyond Friday at this time.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
LIFR restrictions this morning then improving conditions mid to
late morning as a cold front approaches. VFR expected after
18z.

Showers are focused across central SC early this morning near a
surface low pressure area. As the low moves northeast of the
area, the showers will diminish near the terminals by around
16z. IFR or LIFR ceiling and visibility restrictions are
expected to improve toward 18z as mixing develops ahead of a
cold front. The cold front appears to move through the region
around 17z-18z and expect scattered to broken strato-cumulus
into the afternoon then clearing. Light southwest winds will
shift to west and increase to 20 to 30 kts through the afternoon
then diminish after 00z Monday.

.EXTENDED AVIATION OUTLOOK...No significant restrictions are
expected Sunday night into Monday, but could return on by late
Tuesday as a low pressure system develops off the SC/GA coast.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...Lake Wind Advisory from 10 AM this morning to 11 PM EST this
     evening for SCZ016-018-020>022-025>031-035-037-038-041-
     115-116-135>137.
GA...Lake Wind Advisory from 10 AM this morning to 11 PM EST this
     evening for GAZ040-063>065-077.

&&

$$