textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Ice Storm Warning remains in effect due to difficult travel conditions, but is expected to be downgraded to a Winter Wx Advisory by 4 AM.

The Extreme Cold Watch has been upgraded to a Warning, and a Cold Weather Advisory has been issued for the rest of the mountains.

KEY MESSAGES

1. In collaboration with neighboring offices, the Ice Storm Warning will remain in effect until around 4 AM, at which point it will be replaced with a Winter Wx Advisory in light of continued travel difficulties this morning. 2. Gusty northwest winds will combine with falling temperatures to produce dangerous wind chills across the North Carolina mountains and portions of the Georgia mountains this morning, where a Cold Weather Advisory remains in effect until 10 AM. Still lower wind chills are expected tonight into Tue morning. The Extreme Cold Watch has been upgraded to a Warning, while a Cold Weather Advisory has been issued for the remainder of the mountains. 3. Extended cold wave is expected, as temperatures will remain well below normal through the end of the week. Dangerously cold wind chills may return to higher mountain elevations Wednesday through Friday nights. 4. Small possibility of snow next weekend with development of coastal low pressure to our east or southeast. If snow were to fall, it could easily reintroduce or worsen travel impacts due to the cold temperatures prior to onset.

DISCUSSION

Key message 1: In collaboration with neighboring offices, the Ice Storm Warning will remain in effect until around 4 AM, at which point it will be replaced with a Winter Wx Advisory in light of continued travel difficulties this morning.

Precip has largely shifted east of the forecast area early this morning. The only exception is near the TN/NC border, where strengthening NW/upslope flow interacting with moisture banked against the western slopes of the Appalachians is resulting in some light precip. Based upon satellite-derived cloud top temps, this is most likely drizzle with perhaps some freezing drizzle or rime icing in colder areas. However, cold air advection will surge into the area within the next 1-2 hours, and temps in the moist layer will plummet such that snow showers will become the primary precip type by daybreak. Moisture will remain shallow and NW flow will be somewhat veered until later this morning (when the moist layer will be quite shallow), so accumulating snow showers are unlikely.

Otherwise, fog and low stratus linger much of the area this morning in association with shallow moisture atop a sleet-covered ground. Northwest low level flow will steadily overspread the remainder of the area this morning, with downslope flow and dry air advection taking care of the low clouds beginning around daybreak, with sunny skies expected across all but the TN/NC border areas by late morning. Cold advection and sleet pack are expected to yield max temps of 10-15 degrees below climo.

Key message 2: Gusty northwest winds will combine with falling temperatures to produce dangerous wind chills across the North Carolina mountains and portions of the Georgia mountains this morning, where a Cold Weather Advisory remains in effect until 10 AM. Still lower wind chills are expected tonight into Tue morning. The Extreme Cold Watch has been upgraded to a Warning, while a Cold Weather Advisory has been issued for the remainder of the mountains.

Mountain winds will continue to increase through the morning, with gusts of 35 to 45 mph likely developing across the high elevations and in the downslope areas of the Blue Ridge by late morning. This falls a little shy of Wind Advisory criteria, but it will be notably windy.

Temperatures will fall through the lower teens and single digits after sunset today, culminating in widespread min temps in the lower single digits to around zero across the mountains Tue morning. Wind chills are forecast to fall to -15 or lower across Avery County, above 3500 feet across the remainder of the Tennessee border counties, and in the high elevations of northern Jackson County. The Extreme Cold Watch has been upgraded to a warning in these areas for tonight. Most of the remainder of the mountains are expected to meet or exceed Cold Weather Advisory criteria. Even in areas of the southern mountains, where the forecast falls a little shy of criteria, power outages resulting from yesterday's ice suggest it's prudent to issue an Advisory for all of the mountain zones that are not in the Warning.

Key message 3: Extended cold wave is expected, as temperatures will remain well below normal through the end of the week. Dangerously cold wind chills may return to higher mountain elevations Wednesday through Friday nights.

We will be stuck in this pattern thru the week, with a polar vortex over eastern Canada and northeastern CONUS. A series of vort lobes will swing thru the vortex and keep reinforcing very cold air southeastward across the region. A shortwave will cross the area Wednesday, which will keep winds up a bit Wednesday night, likely producing wind chills below zero across much of the elevations above 3500 ft, flirting with Cold Weather Advisory criteria. Another shortwave/strong vort lobe will pivot around the polar vortex and drop south thru the Midwest and Ohio Valley Friday. This will allow another arctic high to slide south across the middle of the CONUS, tightening the pressure gradient across the CWFA and possibly keeping winds elevated Friday night. Cold weather Advisory criteria may be met even outside the mountains in spots, as low temps dip into the teens. Even if we don't meet objective wind chill criteria, the extremely cold temps may have an impact on infrastructure and those vulnerable to the cold. All three of our climate sites: AVL, GSP, CLT look to be well within Cold Wave criteria heading into the next weekend, so a Special Weather Statement may be issued to address the concerns. Highs mainly in the mainly in the 20s to upper 30s in the mountains, and upper 30s to lower 40s in the Piedmont, with lows in the teens to lower 20s. Overall, the pattern will be dry thru at least Friday, with the exception of a few NW flow snow showers near the TN border with the frontal passage Wednesday night.

Key message 4: Small possibility of snow next weekend with development of coastal low pressure to our east or southeast. If snow were to fall, it could easily reintroduce or worsen travel impacts due to the cold temperatures prior to onset.

The latest models are coming into a little better agreement on a sharp vort lobe carving a deep trough over the Southeast late Friday into Saturday. This wave may provide energy to induce cyclogenesis somewhere near the South Atlantic Coast. The low looks to likely form offshore the Carolina Coast, resulting in largely dry conditions for our area. There still could be some brief NW flow snow shower activity with the passing upper trough, but confidence of any precip east of the mountains remains low. A handful of ensemble members from each of the GEFS/EC/GEPS and the AI ensembles all have some QPF over our Piedmont with a possible precip shield extending NW of the coastal low. The air mass in place would be so cold, that the most likely precip type would be all snow for our area. The latest NBM PoPs are still only in the 10-20% range Friday night thru Saturday. But this situation bears watching, as such cold temps ahead of this system would make even light snow stick to roads more than usual, and lead to slippery conditions.

AVIATION /06Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: ***AMD NOT SKED will be carried at KHKY until further notice due to ASOS outage.*** Precip has cleared the TAF sites, but cig/visby restrictions linger across the Terminal Forecast Area as moisture remains abundant, albeit increasingly shallow atop a sleet-covered ground. Drier is beginning to filter into the far western part of the area and strengthening NW winds associated with a cold front. This has resulted in recent improvement to an IFR cig w/ VFR visby at KAVL. KAVL is expected to improve to MVFR by 09Z, with scattering clouds/VFR conditions expected by 10 or 11Z. Meanwhile, IFR/LIFR visby and LIFR cigs are expected to persist at the other sites until 10Z...give or take an hour, with quick improvement to VFR expected. VFR/mostly SKC conditions are expected from around sunrise onward. NW winds will remain at around 15 kts at KAVL through much of the period, with gusts increasing to 25-30 kts later this morning. Occasional gusts greater than 30 kts are possible there this afternoon. Light/variable or light WSW winds at the other sites will steadily turn toward the WSW and increase to around 10 kts by around sunrise, and slightly increase through the morning.

Outlook: Gusty NW winds will continue into Monday night, especially over the mtns. Otherwise, VFR conditions are expected to continue thru much of the week under a cold and dry air mass.

CLIMATE

RECORDS FOR 01-27

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 80 1999 17 1940 54 1916 2 1986 KCLT 75 1890 24 1940 58 1890 6 1940 KGSP 73 1954 29 1940 57 1949 8 1940

RECORDS FOR 01-28

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 75 1914 7 1897 52 1916 -2 1986 1897 KCLT 79 1944 20 1897 59 1916 5 1986 KGSP 77 1944 29 1986 55 1957 5 1986

RECORDS FOR 01-29

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 76 2002 25 1977 52 1917 -1 1897 1897 KCLT 79 2002 29 2014 59 1957 8 1897 KGSP 78 2002 27 1897 57 1957 6 1897 1916

RECORDS FOR 01-30

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 76 2002 11 1966 55 1950 -7 1966 1914 KCLT 78 2002 19 1966 59 1914 4 1966 KGSP 76 1975 20 1966 53 2002 -6 1966

RECORDS FOR 01-31

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 78 1975 13 1909 57 1950 1 1966 KCLT 77 1975 27 1909 59 1950 4 1966 KGSP 79 1975 31 1934 60 1950 3 1966 1909

RECORDS FOR 02-01

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 74 1950 22 1898 55 1950 4 1909 KCLT 76 1950 27 1900 55 1896 10 1900 KGSP 73 1957 30 1980 56 1969 9 1900 1936 1950 1916

GSP WATCHES/WARNINGS/ADVISORIES

GA...Ice Storm Warning until 1 PM EST this afternoon for GAZ010-017- 018-026-028-029. Cold Weather Advisory until 10 AM EST this morning for GAZ010. Cold Weather Advisory from 6 PM this evening to noon EST Tuesday for GAZ010-017. NC...Ice Storm Warning until 1 PM EST this afternoon for NCZ033- 035>037-049-050-053-056-057-062>065-068>072-082-501>510. Cold Weather Advisory until 10 AM EST this morning for NCZ033- 048>053-058-059-062>065. Cold Weather Advisory from 6 PM this evening to noon EST Tuesday for NCZ048>053-058-059-062>065-501-503-505-507- 509. Extreme Cold Warning from 6 PM this evening to noon EST Tuesday for NCZ033-048>052-059. SC...Ice Storm Warning until 1 PM EST this afternoon for SCZ008>014- 019-101>109. Cold Weather Advisory from 6 PM this evening to noon EST Tuesday for SCZ101>103.