textproduct: Greenville-Spartanburg

SYNOPSIS

Dry high pressure builds into the region tonight through Tuesday. Another cold front may bring precipitation chances back Wednesday night into Thursday, mainly in the mountains. Cold high pressure builds in behind that front Friday into next weekend.

NEAR TERM /THROUGH MONDAY/

As of 118 PM EST Sunday:

Key Message #1: Gusty winds through this evening may lead to isolated power outages and difficult travel, especially at higher elevations. The combination of gusty winds and drier conditions will lead to fire weather concerns for locations that lacked rainfall from Saturday.

The secondary cold front behind the initial cold front from last night has brought in reinforced CAA with strong wind gusts. Gusts up to 45-55+ mph have been reported at higher elevations, leading to confirmed Advisory level gusts. The boundary layer supports gusty winds outside the mountains too via forecast soundings and that has also been confirmed with several locations reaching gusts of 35-45 mph, with a few locations exceeding 45 mph as the front continues to push east of the mountains across the Piedmont zones this afternoon. The cold front can best be depicted by the dew point gradient as it should slip east of the CWFA over the next few hours, but even that is getting hard to depict as peak heating mixing has allowed dewpoints ahead of the boundary to tank as well. Gusts are expected to gradually subside as the boundary layer weakens and the pressure gradient relaxes as the surface high behind the front settles over the southern Appalachians overnight tonight.

On top of the gusty winds, elevated fire weather concerns are in store for the southeast fringe of the CWFA. Little to no rainfall fell in this area Saturday, while a cooler and drier airmass settles in today. RH Values will near 25% with gusts of 30-40+ mph, leading to elevated fire weather concerns within the post frontal mixing regime. Red Flag criteria may be reached briefly in these locations this afternoon.

After coordination with the Raleigh NWS office and the NCFS, we have issued a Fire Danger Statement for Union County, NC for the afternoon hours. Also in coordination with the Columbia NWS office, we have issued a Fire Danger Statement for the Lower Piedmont of South Carolina through the early evening hours.

Key Message #2: Ongoing snow showers creating difficult travel conditions and reduced visibility across the mountains, especially along the immediate Tennessee Border.

Northwest flow snow has developed as shallow low-level moisture and potential instability has become fully realized thanks to upslope enhancement and in association with the vort max within the base of the upper trough axis as it currently moves across the CWFA. Some of the snow showers have broke containment from the immediate Tennessee border, producing snow showers across portions of the French Broad Valley and adjacent foothills. Expect this activity to subside over the next few hours as well once the trough axis pushes east of the area and dry air entrainment behind the front disrupts any leftover northwest flow snow by this evening. Some of the embedded snow bands have produced snow squall-ish type conditions with the gusty winds and reduced visibility.

Lighter winds and much cooler temperatures will be in store overnight tonight as any clouds should clear with the exception of the immediate Tennessee border with ongoing northwest winds. With good radiational cooling conditions, expect overnight lows to run 5-10 degrees below normal. Surface high will fully set up shop across the Southeast on Monday as a surface lee trough helps veer winds out of the southwest by Monday afternoon. With partly to mostly sunny skies expect afternoon highs on Monday to be near-normal.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/

As of 1225 PM EST Sunday...

Key Message #1: Dry and quiet weather expected through the first half of the workweek.

Quiet weather will continue on Tuesday as high pressure lingers across the Southeast. An upper trough will dig across the Great Lakes and bring a cold front into the Ohio Valley. Dry conditions will continue, with dewpts likely mixing out lower than the NBM once again Tuesday aftn. Winds should remain fairly light out of the W/SW, but there could be elevated fire weather concerns in our far southeast zones, which didn't get much rain recently, as RH values approach 25%. Temps will warm to a few degrees above normal under sunny skies. As the front approaches from the NW Wednesday, moisture/cloud cover will increase atop the CWFA, while SW winds pick up and become breezy in the aftn. PoPs ramp up into the chance range along the TN border by the end of the day, but should start out as mainly rain showers, with temps still a few degrees above normal.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

As of 1245 PM EST Sunday...

Key Message #1: A northwest flow snow event may bring some minor accumulations across the mountains, mainly near the TN border Wednesday night through Thursday.

The latest guidance has come into better agreement on a dynamic/strongly-forced trough swinging through the OH/TN valleys and even closing off into an upper low as it reaches the Southern Appalachians by Thursday. This forcing will have enough moisture to work with, and may be enhanced by a zone of frontogenesis that pushes into the mountains from the west. Dry westerly to west-southwesterly flow east of the mountains will limit PoPs. But 850 mb temps fall Wednesday night in the mountains as moisture ramps up. So confidence is increasing on at least advisory-level snow accums along the TN border in the usual NW flow upslope areas. Most of the snow looks to fall Wednesday night thru Thursday morning. A sfc low will likely form in response to the upper low, somewhere invof the Central Appalachians or Mid-Atlantic Thursday. This may allow some wrap-around moisture to spill east of the mountains Thursday. But per usual, temps will start out a little too warm for snow east of the mountains, and it will be race between the moisture and cold air. But if moisture can linger long enough during the day, we could see some snow flakes outside the mountains in spots. Confidence remains low, and even if somehow the cold air and moisture overlap, snow accums should be spotty and light.

Key Message #2: Arctic air returns Thursday night into Friday, ushering in gusty winds and dangerous wind chills in the high elevations. Below-normal temperatures continue through next weekend.

Temps expected to plummet into the single digits and teens behind an arctic front Thursday night across the high terrain. Winds will be gusty, but expected to stay below advisory criteria, except for the highest peaks. But wind chills may dip into the -5 to -10 deg F range above 3500 ft in the northern mountains overnight thru daybreak Friday. Lows in the Piedmont will be in the upper teens to lower 20s.

Cold air will remain in place heading into the weekend, as a series of shortwaves reinforce a deep upper trough across the eastern CONUS. There remains a lot of disagreement among the guidance on a potential southern stream shortwave that could bring moisture into the region over the weekend. The system may be similar to the midweek storm, with mainly a NW flow snow event and some showers breaking containment east of the mountains as the system departs. But the 00Z ECMWF and 12Z Canadian have come in drier with the system. The latest NBM has slight chc to low-end chc ramping up mainly in the mountains late Saturday. Otherwise, it should be dry with temps remaining below normal.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR conditions will prevail through the forecast period. The main topic of discussion will be the winds through this evening as west to northwesterly winds have really picked up behind a cold front to go along with deep mixing. Expect gusts through the afternoon at 25-35 kts, with some higher gusts not being ruled out. Gusts should gradually subside by 00Z Monday and completely diminish overnight tonight. FEW/SCT 050-060 stratocu has broke containment across the mountains and has passed over the TAF sites. That should also taper off later this afternoon outside of KAVL, where SCT/BKN 030-045 cigs will likely linger into the overnight hours before diminishing. Partly to mostly sunny skies in store for all TAF sites on Monday as winds start out the day light and variable and pick up out of the southwest at 5-10 kts by the afternoon.

Outlook: Expect dry VFR conditions for the first half of the week with surface high pressure over the region. Another frontal system will approach on Wednesday and may bring showers and associated restrictions. Some wintry precip could affect KAVL early Thursday morning.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Wind Advisory until 6 PM EST this evening for NCZ033-048>053- 058-059-062-063. Increased Fire Danger until 6 PM EST this evening for NCZ082. SC...Increased Fire Danger until 7 PM EST this evening for SCZ009- 011>014-019.