Wade Hampton, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

371
FXUS62 KGSP 180609
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
109 AM EST Sat Jan 18 2025

.SYNOPSIS...
Low pressure moving across the region will provide widespread rain
this morning, with a wintry mix across portions of the mountains. A
round of light snow showers could develop late tonight or Sunday
near the Tennessee border. Arctic high pressure returns Monday
bringing bitter cold to the region for next week. A storm system
is expected to track from the northern Gulf of Mexico to off the
Southeast Coast midweek.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1250 AM Sat: A key feature of interest for the short term
will be the shortwave trough now centered over the Ozarks, progged
to dampen slightly as it tracks thru the Ohio Valley today. An
associated warm front extends from NE AR to N GA presently. An arc
of generally light precip will move into our western zones over
the next 2-3 hours. Observed temps are either side of freezing in
the mountains, partly dependent on elevation, but most areas above
freezing still have wet-bulb temps that are below. Precip will have
to overcome dry air to begin, but it still would appear light snow
or sleet will occur where wet-bulbs are cold enough. Precip coming
in a little later than originally forecast, but still likely to
be widespread over the mountains by around 5-6 AM, expanding east
with the aid of dynamic lift and subsequently as the warm front
rides north/east into the area later this morning. Main changes
this update were to Sky/Wind for aviation update but will be making
a full reassessment of PoP/p-type by the 3:30 AM package.

As alluded to above, precip will have to fight its way down to the
surface as it will be developing into a dry sub-cloud air mass. As
this happens, wet-bulb effects will cool the remnant subsidence
inversion layer across the region and re-orient the atmospheric
column to be essentially isothermal above the sfc up to about 8K
feet, after which the temp drops off as expected. What this means
is we are looking at an elevation-dependent rain v. snow scenario,
apart from the usual possible brief mix with sleet at onset. The
forecast temp/dewpt will be important and will be the main driver
of what reaches the ground. Temps should stop falling as the clouds
thicken, and should actually start to rise toward daybreak. Snow
levels will most likely be around 3K-4K ft MSL. Fortunately,
the QPF is relatively light, so that limits the snow accum to
1-2 inches at the highest elevations, and limits the potential
for getting to Advisory criteria in most places outside of the
Smokies, Balsams, and Nantahala Mts. Outside the mtns, this should
allow for a brief mix of rain/snow at the onset along/N of I-40,
but a changeover early in the day. No Advisory due to expected
low impact. As temps warm, precip will changeover to all rain
later this morning even at the high elevations. The better upper
divergence and DPVA will move off late in the morning, taking the
high precip probs with it. However, some weak forcing will remain
along/ahead of the approaching cold front as it stalls briefly
over the mountains. That should keep some low precip probs into
the afternoon, but most places will see something of a lull in
the mid/late afternoon, even as the day ends up cloudy and damp,
with temps just below normal.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
As of 3:19 PM EST Friday...An active short-term is in store with the
approach of an arctic front. This boundary will likely be situated
near the TN-NC border Saturday evening, but the real cold arctic air
will lag upstream over the Midwest. A wave of low pressure over the
Gulf States is expected to track northeastward along the boundary,
passing directly through the area late Saturday night into Sunday
morning. The front will temporarily stall Saturday night when the
flow backs out of the south ahead of the low. Precipitation may
develop along and east of the low track in the eastern Piedmont
region, but the forcing is shallow, so amounts will be light.
Thermal profiles support one ptype in the piedmont region - rain.
Another area of light precipitation is favored to develop across the
mountains as the boundary-layer flow shifts from the northwest,
producing orographic lift. There is a risk for a light glaze of
freezing rain in the mountains at elevations above 3500 ft where
temperatures hover in the upper 20s and lower 30s. The HREF shows 50-
60 percent probabilities of at least 0.01" of ice accretion.

Northwest winds on the backside of the surface low will allow the
arctic front to surge southeastward across the area on Sunday. This
will be accompanied by a chanalong or jgeover to snow showers from
west to east across the mountains during the mid to late morning.
There is a possibility that some convective snow showers make it
pass the mountains and into the NC Foothills or even Piedmont region
as the front sweeps eastward during the afternoon and early evening.
Snow accumulations of 1-2" are forecast in the Central and Northern
Mountains near the TN-NC border.

A tight pressure gradient as the arctic high builds in will yield
gusty winds. The highest winds are expected in the western NC
mountains where the probability of gusts in excess of 45 mph (Wind
Advisory criteria) range between 30-60 percent late Sunday night-
Monday morning. Strong cold air advection will yield a sharp drop in
temperatures behind the arctic front on Sunday. That pattern will
continue into Sunday night-Monday morning, marking the arrival of
the coldest airmass of the winter thus far. The combination of the
cold air and brisk wind will yield frigid wind chills. LREF
probabilities of Cold Weather Advisory criteria by early Monday
morning are 10-20% in the Lower/Eastern Piedmont and 20-30 percent
in Northern Piedmont and Foothills, and SC/GA Mountains, increasing
to 70-80% in the NC mountains. Later shifts will consider the need
for an Extreme Cold Warning in the Northern Mountains of NC.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 3:19 PM EST Friday...The arctic airmass will build overhead
Monday night and Tuesday. This will yield a very cold start to the
period with temperatures 20 degrees below normal for what is
climatologically the coldest time of the year through Wednesday.
Sunny skies will offer little consolation to the frigid conditions
with temperatures struggling to rise above freezinstillg across much
of the area. Additional Cold Weather Advisories may be needed Monday
night and Tuesday night where LREF probabilities of reaching
critieria range between 20-40% in the eastern Piedmont, increasing
to 40-60 percent in the Charlotte metro, and 50-70% in the northern
mountains.

An area of low pressure is expected to organize on the southwestern
periphery of the arctic front over the northern Gulf of Mexico late
Monday-Tuesday. Models continue to converge toward the low taking a
northeast track either just off the SE US coast (most likely over
the Gulf Stream) midweek. While thermal profiles will definitely
support all snow, the heaviest precipitation, and possibly all the
precipitation, will likely stay east of the area and closer to the
coast. Probabilities from the NBM for at least a dusting of snow are
around 30-40 percent in our far eastern zones, which could with cold
enough ground temperatures, could cause issues if it falls during
the Tuesday evening rush.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Cigs start off 150-200 but will lower
below 060 before daybreak. Precip shield initially driven by
shortwave will shift over the TAF terminals from west to east
between approx. 09-15z. Periods of MVFR vsby and cigs will be
possible as a result. In higher elevations and in cooler parts of
the NC Piedmont -SN or -PL could mix in near onset but rain will
predominate; this chance looks best (and mentionable) at KAVL, and
can`t be ruled out at KHKY although too unlikely to mention. This
wave of precip likely will exit to the east or diminish by midday,
but a warm front subsequently will activate as sfc low moves
into MS/AL. Cigs may lift or scatter for a time after precip but
MVFR to IFR stratus cigs will develop ahead of the warm front,
lowering to LIFR in most areas by early evening. A second round
of light/brief precip could pass over KGSP/KGMU/KAND this aftn or
evening, although this is of low enough consequence to mention
only as -DZ or VCSH for now. Good signal for IFR (or worse) fog
developing across most of the region tonight, likely affecting
all sites. Winds generally light southerly, although turning NW
at KAVL this evening if not going calm.

Outlook: NW flow snow showers possible Sunday near the NC/TN border,
NW of KAVL, mainly in the morning. An Arctic airmass will spread
into the region late Sunday into Sunday night, bringing exceptional
cold to the region which will last most of next week. Small chance
of snow Tue evening thru early Wed.

&&

.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...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...JK/Wimberley
NEAR TERM...PM/Wimberley
SHORT TERM...JK
LONG TERM...JK
AVIATION...Wimberley
CLIMATE...GSP