textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Special Weather Statement for Increased Fire Danger was issued for the North Carolina Piedmont from Noon to 6 PM EST Friday.

Special Weather Statement for Increased Fire Danger was issued for the northeast Georgia from Noon to 7 PM EST Friday.

Snow totals have decreased for Friday night and snow chances for locations east of the mountains has decreased for Saturday night.

KEY MESSAGES

1. Frigid Arctic air will remain in place through the morning before rebounding this afternoon. The combination of cold temperatures and gusty winds will produce very cold wind chills, especially at higher elevations through the morning hours. 2. Fire weather concerns return across the North Carolina Piedmont, South Carolina Upstate and Northeast Georgia this afternoon thanks to low relative humidity and breezy winds. 3. Light snow accumulations over the North Carolina mountains and possibly the mountains of northeast Georgia and the Upstate tonight through Saturday morning could result in minor travel issues, mainly at high elevations. 4. A potential system moves into the area with a slight chance for rain or snow east of the NC mountains. Impacts look to be minimal at this time as accumulations are trending down. 5. Another cold air mass could settle over the region by the middle of next week. A Cold Weather Advisory may be needed for parts of the mountains Monday night into Tuesday.

DISCUSSION

Key Message 1: Frigid Arctic air will remain in place through the morning before rebounding this afternoon. The combination of cold temperatures and gusty winds will produce very cold wind chills, especially at higher elevations through the morning hours.

Lingering gusts from ongoing CAA and anomalously cold thicknesses, expect very cold wind chills, especially in the higher elevations where a Cold Weather Advisory remains in effect through 7 AM in elevations above 3500' with values as low as 15 degrees below zero are expected. Visibility restrictions can't be ruled out as well due to blowing snow that gets kicked up from the lingering wind gusts. Otherwise, cyclonic flow aloft will remain in place as a closed upper low churns over the Northern Plains and Upper Great Lakes region. The surface high that's currently situated over the southeastern CONUS will quickly shift offshore throughout the daytime period, allowing for a low-level south to southwesterly return flow. In this case, expect temperatures to rebound compared to Thursday as afternoon highs will be up to 5 degrees below normal, with low-end gusty winds.

Key Message 2: Fire weather concerns return across the North Carolina Piedmont, South Carolina Upstate and Northeast Georgia this afternoon thanks to low relative humidity and breezy winds.

Antecedent dry airmass currently in place will support increased fire danger for locations outside of the mountains as boundary layer mixing during peak heating keep dewpoints mixed with values in the single digits to lower teens, while the actual temperatures rise throughout peak heating. Factor in breezy south to southwest winds (gusts: 20-25 mph) mixing down from the top of the boundary layer (~850-825mb) during the afternoon, to go along with dry fuels and RH values below 25%, and fire concerns will become realized. As a result, a Fire Danger Statement was issued for the North Carolina Piedmont from Noon to 6 PM EST and portions of northeast Georgia from Noon to 7 PM EST. Additional Fire Danger Statements may be needed for the South Carolina Upstate, but will continue to monitor through the rest of the morning hours.

Key Message 3: Light snow accumulations over the North Carolina mountains and possibly the mountains of northeast Georgia and the Upstate tonight through Saturday morning could result in minor travel issues, mainly at high elevations.

The aforementioned upper low over the Northern Plains will send a vort max eastward with an attendant cold front riding underneath, with the vort max lifting north of the area Saturday, but should be strong enough to push the front through the area during the day Saturday. Strong enough forcing from upper divergence aloft via jet streak and isentropic ascent should help overcome the lack of strong moisture return overnight tonight into Saturday morning, supporting precip to develop over the Smokies and southwest mountains shortly before or around midnight. West-southwesterly upslope will help enhance PoPs in this region as well. The onset of precip should be mostly snow or sleet via wetbulb as the precip works down to the surface through evaporational cooling. CAMs show this activity spreading east into the northeast Georgia mountains and foothills, as well as the western portions of the Upstate through the pre-dawn hours Saturday before drying up further east as the better forcing lifts north of the area. Can't rule out snow or sleet at the onset in these locations as well before turning to all rain in the lower elevations as the precip moves into the CWFA during the coolest part of the diurnal cycle, with little to no accumulation expected. The precip will continue across the mountains through the overnight period, and into the morning hours with colder air in place. Soundings show a layer of warmer air above freezing between 800-925mb, which would support more of a mix, even predominately light freezing rain near the Southern Blue Ridge Escarpment, Balsams, and sheltered valleys in the southwest mountains. In this case, can't rule out a light glaze of ice in these locations, but the area of concern is too isolated for an Advisory at this time. Snow will continue at the higher elevations (>3500'), with 1-3" (locally higher on the ridgetops) not being ruled out in the Smokies and portions of Avery County. Likely will support this event with an SPS and HWO mention at this time unless trends increase leading up to the start of the event. Most of the precipitation will diminish by Saturday afternoon as the trailing frontal boundary slips across the CWFA, inducing dry air entrainment behind it. Some breaks of sunshine in the afternoon to go along with recovering heights should allow afternoon highs on Saturday to return to near-normal values, especially in locations outside of the mountains, with slightly below normal readings in the High Country.

Key message 4: A potential system moves into the area with a slight chance for rain or snow east of the NC mountains. Impacts look to be minimal at this time as accumulations are trending down.

The persistent trough over the eastern portion of the CONUS, digs into the south on Saturday night and lifts NE through Sunday. At the surface, a very strong frontal boundary extends to the Gulf with a wide tongue of surface moisture ahead of it. Current guidance is trending down as drier air cuts off precip potential, especially over the mountains. QPF response is minimal and remains well east of the I-85 corridor. Model soundings for areas along and east of I-85 show a brief window early Sunday morning for snow to develop aloft, as surface temperatures hover near freezing. This window looks to quickly narrow as a potential dry slot develops in the mid-levels as downslope winds develop in the late morning hours. Another potential pitfall for the event points at the downslope winds that could keep temperatures too warm for any snow, keeping anything that falls as rain. At this time, the potential for areas east of the mountains, especially along and east of I-85 to see more than a 0.1" amount of snow is 20-30%. The chance for an inch or greater of snow is less than 5%, which has decreased since the last forecast cycle. Confidence in this system is low. Impacts are expected to be minor as roads should remain warm.

Key message 5: Another cold air mass could settle over the region by the middle of next week. A Cold Weather Advisory may be needed for parts of the mountains Monday night into Tuesday.

On the back end of a deep upper trough, a strong area of surface high pressure dives southward into the central CONUS and spreads eastward. Winds with this system look to increase as well. Drier air could usher in very cold temperatures, especially for the mountains. This combination of winds and temps increase the chances for wind chills to dip into the Cold Weather Advisory range for Monday night. At this time, there is a 50-60% chance for the mountains to be 10 degrees or colder with wind chills below zero. Confidence is low to medium as there are still many things that could change over the next few days.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: VFR conditions are expected through the 06Z TAF forecast period. Any lingering wind gusts have subsided outside of the higher terrain. Winds are generally west to southwesterly currently and should turn to a south to southwesterly component after daybreak as winds increase to 6-12 kts with low end gusts by this afternoon. KAVL will maintain a north to northwesterly wind before switching to a southerly direction by the afternoon. Cirrus is expected to gradually increase through this morning and afternoon. A storm system will approach the area tonight into Saturday morning, bringing next chance of precip and associated restrictions, which will likely be introduced during the 12Z TAF update.

Outlook: A cold front may bring precipitation and associated restrictions this weekend, but confidence remains low. Dry and VFR conditions should return by early next week.

GSP WATCHES/WARNINGS/ADVISORIES

GA...INCREASED FIRE DANGER from noon EST today through this evening for GAZ018-026-028-029. NC...INCREASED FIRE DANGER from noon EST today through this evening for NCZ036-037-056-057-068>072-082-508. Cold Weather Advisory until 7 AM EST this morning for NCZ033- 048>052-058-059-062-063. SC...None.