textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Rain and thunderstorm chances increasing for another system toward the end of the week.

KEY MESSAGES

1. Snow with gusty NW winds continue across portions of the mountains near the NC/TN border through tonight, with below normal temperatures through Tuesday. Impacts from the snow could create hazardous travel conditions in these locations. 2. Near-critical fire weather conditions are expected each afternoon through Tuesday. 3. Temperatures warm throughout the week, with a cold front increasing rain and possible thunderstorm chances across the area early Thursday into Friday.

DISCUSSION

Key message 1: Snow with gusty NW winds continue across portions of the mountains near the NC/TN border through tonight, with below normal temperatures through Tuesday. Impacts from the snow could create hazardous travel conditions in these locations.

The increasing surface pressure gradient between the low pressure system to the north and the strong surface high building into the central CONUS, keeps gusty NW winds and snowfall for a portion of the mountains through tonight. The ongoing Winter Weather Advisory and Winter Storm Warning remain in effect through 12 AM Tuesday. Wind gusts look to be below any advisory criteria, especially below 3500'. However, wind gusts above 3500' are likely to have gusts of 45-55mph, which were mentioned in the ongoing products. As the low and trough continue to pull away from the region today, expect winds to diminish tonight. Strong winds across the Upstate of SC and NC Piedmont of 20-30 mph still on track for this afternoon, but remain below any wind advisory criteria. As for accumulating snowfall at the NC/TN border, an additional 1-4 inches possible with 4-7 inches at the highest peaks through late this evening, especially for locations above 3500'. Latest guidance does indicate the snow tapering off through this evening.

Additionally, another round of frigid wind chills tonight, though not as cold as this morning as winds are expected to drastically decrease overnight. For the mountains, wind chills into the single digits and east of the mountains should be in the upper teens and lower 20s. By Tuesday morning, these temps should rebound a bit and warm into the upper 40s and lower 50s, with a few locations in the mountains still clinging to colder temps.

Key message 2: Near-critical fire weather conditions are expected each afternoon through Tuesday.

Sustained winds out of the NW of 15 to 25 mph, with gusts generally in the 40-50 mph range are expected across the mountains through late this afternoon before diminishing overnight. Locations east of the mountains are expected to see near-critical RH of 25-30% this afternoon. These conditions elevate the fire danger, especially across the foothills, where a wetting rainfall failed to occur Sat/Sat night.

For Tuesday, widespread critical RH of 15-20% is expected across most of the area. Unlike Monday, winds should be considerably weaker and out of the SW at 5-10 mph. Despite less winds, the fire danger continues to be elevated mostly for locations east of the NC counties bordering TN, where at least some snowpack is expected to linger into Tuesday. Though the overall fire danger will be elevated, below-normal temperatures could be a limiting factor.

Key message 3: Temperatures warm throughout the week, with a cold front increasing rain and possible thunderstorm chances across the area early Thursday into Friday.

Guidance continues to signal for a short wave trough swinging through the area by the end of the week, increasing shower and possibly thunderstorm chances. By Thursday, guidance depicts a developing surface low moving northeast, dragging a robust cold front across the TN/Ohio Valley and into the CWA. How much of this FROPA survives the mountains is yet to be determined. Current guidance swings it through Thursday night and into Friday morning, but this could change. As of the current trends, the likelihood of this system bringing at least 1" of rainfall has increased 60-70%, mainly for the far western NC mountains. As far as thunderstorm potential, one limiting factor at this point is timing of the front moving through overnight. This keeps instability very low if not nonexistent. Current probs has about a 20-30% chance of at least 50 J/KG of sbCAPE overnight, mainly east of the mountains and closer to the SC/GA border. This is a slight increase in probs from previous forecasts, but confidence remains low for any severe potential. Cannot rule out a rumble of thunder or higher convective rain rates, but this will continue to be monitored.

AVIATION /06Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: The main problem for the overnight and early Monday will be the ongoing light snow at KAVL. Satellite and radar imagery show a decent streamer of light reflectivity and cold cloud tops more or less oriented with the French Broad Valley. Beneath this streamer, light snow continues to fall, restricting the vis to MVFR-levels, while the ceiling was bouncing up and down either side of the 030 threshold. See no reason why this shouldn't continue well into the pre-dawn hours, so prevailing MVFR will be carried for the snow. Elsewhere...a few snow flurries would not be a surprise, but not to the extent that it would be restrictive. Instead, scattered high-based stratocu will be possible, but a gusty NW wind will be more of a concern. VFR at all other terminals. There is some indication of orographic wave cirrus Monday afternoon across the western Piedmont. The gusty NW winds will finally relax after sunset on Monday.

Outlook: Quiet weather returns to the region for Tuesday and Wednesday. Another low pressure system will approach the area on Thursday, bringing showers and associated restrictions.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Winter Storm Warning until midnight EST tonight for NCZ033-050. Winter Weather Advisory until midnight EST tonight for NCZ048>052. SC...None.