290
FXUS62 KGSP 191440
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
940 AM EST Sun Jan 19 2025

.SYNOPSIS...
A round of snow showers will develop this morning near the Tennessee
border and linger through Monday morning, with good snow accumulation
likely at the higher elevations. Arctic high pressure moving in tonight
will bring bitter cold to the region for most of this week. A storm
system is expected to track from the northern Gulf of Mexico to off
the Southeast Coast mid-week, bringing the potential for snow showers
across portions of the area.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 935 AM Sunday...A quick update to remove some of the Dense Fog
Advisory. With the sfc low moving northeast across SC at this time,
the wind has come around to SW over northeast GA and the western
Upstate, and was mixing out the fog and low stratus. Expect another
update in the next hour to remove more of it, and possibly extend
some zones in the east. Otherwise, another update will follow
later this morning.

Otherwise...the surface low will track generally northeast today,
progged to reach the Tidewater region by late afternoon. A
very small amount of elevated instability proggedd above the
inversion is driving some showers near our SE border presently;
similar activity may develop further north into the NC Piedmont
thru midday. They should be all rain if they develop. Skies will
clear as the low passes and downslope flow is induced across
the Piedmont from midday onward. Temps still will be near climo
in the southeastern CWA. However, as winds turn westerly over
the mountains this morning as the low passes by, CAA will begin
which will strengthen this afternoon, and upslope forcing also
begins. Profiles quickly cool and snow levels fall in the TN/NC
border area, such that accumulating snow is likely to begin by
about 9-10 AM; rates are expected to pick up appreciably during the
afternoon as winds orient more NW. Areas along the TN border will
see their daytime highs well before noon, with valleys seeing temps
fall through the afternoon. As noted by previous forecasters, the
upslope layer becomes especially cold supporting much greater snow
ratios than we typically see, likely approaching 20 to 1. Small
SBCAPE is depicted along the TN border which will help enhance
precip production. Rates up to around an inch per hour may occur in
some very high elevations of the Smokies this afternoon; best ice
nucleation occurs after sunset although by then moisture becomes a
bit harder to come by. Retained existing Winter Storm Warnings and
Advisories. A late addition (after 4 AM) was to add high elevations
of Buncombe County, above 3500 feet, to a Winter Weather Advisory,
due to likelihood of accumulating snow in particular along the
ridges northeast of Asheville. Weaverville is likely to see up to
around an inch, and less in the city of Asheville itself.

Sustained winds of 10 to 20 mph, with gusts of up to 40 mph may
occur on ridgetops, and based on expected lows in the single digits
across most of the mountains (below zero on higher ridgetops,
and 10-15 in the foothills), wind chills easily meet previous
expectations of Cold Wx Advisory criteria in valleys/foothills and
Extreme Cold Warning in higher elevations. All areas previously
in Extreme Cold Watch are now in one of those products; Advisory
crtieria look to be met in some adjacent foothills areas so that
was added with this issuance. We miss criteria by only a few
degrees elsewhere in the forecast area

Although the indication is that accums might only be on the order of
1-3 inches in the TN border counties away from the upslope areas,
the dry snow falling into temps below the upper 20s should result
in very slippery road conditions in places where roads are not
treated. This could result in a high impact to transportation.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 3:25 AM EST Sunday...the short-term fcst picks up at 12z on
Monday with very broad upper trofing covering most of the CONUS.
Over the next 24 hrs or so, the trof begins to shift east and de-
amplify as upper ridging builds over the West Coast. Towards the
end of the period early Wednesday, the trof axis is expected to
pass over our area and then lift NE and off the Atlantic Coast.
At the sfc, broad, arctic high pressure will be spreading over
the Southeast as the period begins. The high will linger over our
area into Tuesday and then get reinforced from the west towards
the end of the period late Tuesday into early Wednesday. At the
same time, a low is progged to develop over the Gulf of Mexico
and then quickly move NE and out over the Atlantic. With the cold
air in place during that time, it`s still likely that any precip
that does materialize would be snow for our fcst area. Overall,
precip chances have trended up a bit roughly along and south of
the I-85 corridor, but the QPF amounts remain minimal at best
with only a few hundreths of an inch expected for our fcst area.
Nonetheless, this does produce about a half inch of snow over
our southern/southeastern-most zones late Tues into early Wed.
With the cold sfc/road temps already in place, any snowfall could
produce significant impacts on untreated roads. The other main
concern for the period will be the very cold airmass that lingers
thru the period. This airmass will produce very cold temperatures
and wind chills, especially across the mtns. High temperatures will
struggle to get above freezing each day across most of our CWA.
Winds are expected to be gusty as the period begins Monday morning,
which will likely produce wind chill values below zero across most
of the mtns early Monday with single digit to low teens likely for
most of our lower terrain. Wind chill values aren`t expected to be
as low Tuesday morning as winds should be weaker, however winds pick
up again early Wednesday morning and produce another round of very
cold wind chills early Wednesday.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 3:05 AM EST Sunday...the extended fcst picks up at 12z on
Wednesday with broad upper trofing flattening over our area and
heights briefly recovering. Over the next couple of days, the
backside of the trof will amplify again over the central CONUS
and then translate east and over our region. By early Saturday,
most of the current long-range guidance has the upper trof lift-
ing off the Atlantic Coast with flat upper ridging spreading over
the Southeast to end the period. At the sfc, a moist frontal boun-
dary is expected to be lingering just to our south and east as the
period begins early Wednesday. At the same time, high pressure gets
reinforced from the west across our fcst area and lingers well into
Thursday. By late Thursday, most of the long-range guidance still
tries to develop another sfc low just off the SE Coast and then
quickly move the system northward and up the Atlantic Coast. How
fast this happens still remains unclear amongst the operational
models. At the same time, another trailing cold front is expected
to move thru our area from the west, but it`s looking pretty dry
at this point. In its wake, another broad area of high pressure
will spread back over the Southeast to end the period. As such,
the period remains dry thru the end of the week with solid chance
PoPs by the very end of the period next Sunday. The cold airmass
will still be in place as the period begins, but will gradually
modify as the period wears on. Temps are still expected to remain
well-below climatology thru Friday, but should warm to near-normal
values over the weekend as the period ends.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Low stratus deck over all sites except
arguably KAVL is expected to see little change until 14-15z, at
which time dense fog is expected to begin to dissipate. Periodic
conditions at or even below minima until then. LIFR cigs will take
another hr or two to erode, doing so as weak sfc low passes the area
in the midday timeframe and induces dry/downslope flow. KAVL instead
seems to have valley stratus and proving more variable, still likely
restricted thru late morning. The low could help initiate -SHRA at
the SC sites or KCLT, but these would be of minimal impact beyond
the restrictions--no thunder expected. Winds initially light/VRB,
particularly changing prevailing dir in response to passage of
low. They pick up from the SW late morning except at KAVL where
they should already be NW. Cloud deck scatters to VFR midday to
early aftn. Low VFR to MVFR clouds will persist at KAVL via upslope
into the mtn spine, and a few flurries are not out of the question
but likely of small impact.

Outlook: Gusty NW winds linger at KAVL through Monday. An arctic
airmass will spread over the region Sunday night, lingering much
of the week, bringing exceptionally cold temperatures but mostly
VFR. There is a small potential for snow Tuesday evening into
Tuesday night but confidence remains low.

&&

.CLIMATE...
RECORDS FOR 01-20

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      69 1906     24 2009     53 1954    -13 1985
                1890
   KCLT      71 1951     30 1983     53 1890     -2 1985
                1929        1893
                1927
   KGSP      72 1933     30 1983     56 1922      1 1985



RECORDS FOR 01-21

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      72 1927      8 1985     59 1927    -16 1985
   KCLT      73 1935     24 1985     58 1954     -5 1985
   KGSP      73 1927     26 1985     59 1933     -4 1985



RECORDS FOR 01-22

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      73 1932     21 1960     59 1933      0 1970
   KCLT      74 1937     29 1970     60 1906      5 1970
   KGSP      72 1938     31 1970     58 1933      3 1893
                1921



RECORDS FOR 01-23

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      73 1927     20 2005     54 1999      1 1936
                            1936
   KCLT      75 1927     27 1970     59 1999      9 2003
   KGSP      73 1974     30 1970     58 1999      5 1893
                1927

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Cold Weather Advisory from midnight tonight to noon EST Monday
     for GAZ010-017-018-026.
NC...Cold Weather Advisory from midnight tonight to noon EST Monday
     for NCZ033-048>053-058-059-062>065-501>510.
     Dense Fog Advisory until 11 AM EST this morning for NCZ033-
     035>037-048>053-056>059-065-068>072-082-501>510.
     Winter Storm Warning until 7 AM EST Monday for NCZ033-048>052-
     058.
     Extreme Cold Warning from midnight tonight to noon EST Monday
     for NCZ033-048>053-058-059-062>064.
     Winter Weather Advisory until 7 AM EST Monday for NCZ051-053-
     058-059.
SC...Cold Weather Advisory from midnight tonight to noon EST Monday
     for SCZ101>103.
     Dense Fog Advisory until 11 AM EST this morning for SCZ008>014-
     019-103-105>109.

&&

$$

SYNOPSIS...Wimberley
NEAR TERM...PM/Wimberley
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...Wimberley
CLIMATE...