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. 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. 2. 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. 3. 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. 4. 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: 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 2: 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 3: 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 4: 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 /14Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: VFR conditions are expected through this evening with restrictions filtering in by the end of the forecast period. 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 the next chance of precip and associated restrictions. Most of the guidance suggests that the precipitation will make it to the mountains and Upstate, so placed a PROB30 for SHRA and associated restrictions during the last 6 hours of the forecast period. KAVL should see a mix of wintry precipitation at the onset, so placed a three hour window for SHSNRA between 06-09Z Saturday and going to all rain from 09-12Z Saturday. Guidance quickly brings in MVFR cigs with this system and hints at the potential for IFR as well, which is included in the PROB30. Kept KHKY/KCLT dry for now as the area of precip struggles to make it that far east before dissipating, but will need to be monitored for any updates.

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 until 7 PM EST this evening for GAZ018- 026-028-029. NC...INCREASED FIRE DANGER until 7 PM EST this evening for NCZ036- 037-056-057-068>072-082-508. SC...None.