textproduct: Greenville-Spartanburg

SYNOPSIS

An upper ridge centered over Mexico will keep our region dry and unseasonably warm through the weekend. A backdoor cold front will bring a chance of light showers and relatively cooler temperatures for Friday before near-record high temperatures return on Saturday. Mild and dry conditions are expected on Sunday ahead of a cold front which will bring showers on Monday and usher in arctic air Tuesday through New Year's Day.

NEAR TERM /THROUGH FRIDAY/

As of 1205 PM EDT Thursday:

Key Message #1: Warm for Christmas Day with isolated rain showers possible in the mountains.

The CWA remains caught in the middle between high pressure systems, one to the north and one to the south. The warm temps continue today as the 500mb heights remain relatively steady across the southeast before slowly dropping on Friday. The ridge that plagued most of the central CONUS begins to de-amplify with winds aloft becoming more westerly toward the end of the period. What this means in terms of temperatures are mid 70s again for areas east of the mountains. Since records are higher today at KGSP and KCLT, the likelihood of breaking or tying the records are slim. However, KAVL has a chance for breaking/tying the record which currently stands at 71. Meanwhile, an area of low pressure develops over the Midwest and enhances a baroclinic zone that makes a run for the mountains. Given the amount of surface moisture, there is a brief chance (25-45%) for a very brief shower over areas located along the TN/NC border through tonight and even less of a chance (15-25%) for Friday. Rain totals are dismal at a mere 0.01-0.2" range for the entire near term period.

Key Message #2: Backdoor cold front brings cooler temps for a portion of the area Friday.

Along with the strong surface high moving into the northeast overnight, a backdoor cold front is expected to descend from the NE into the area tonight and Friday. It's a quick moving front which lifts out of the region by the end of the forecast period. Given the amount of moisture still present when the front arrives, cannot rule out a very brief period of sprinkles Friday morning in the NC Piedmont with little to no accumulations. But, the main story of this front will be a 10-15 degree temperature drop for the NC Piedmont on Friday. Since this is a quick moving system, it looks as though the cooler air won't make it into the Upstate in time. However, the area should be a few degrees cooler than today, with temps in the mid/upper 60s and low 70s. For the NC Piedmont, enjoy the 50s.

SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/

As of 1200 PM EST Christmas Day...

Key Message #1: Light northwest flow rain expected across the mountains Friday night into Saturday morning with highs Saturday afternoon rebounding into 70s in the mountain valleys and east of the mountains.

Upper ridging remains aloft while a backdoor cold front stalls across the forecast area through the short term. A sfc low will track from the Ohio Valley into the Mid-Atlantic Friday evening into the early Saturday morning allowing some brief northwest flow rain to develop across the North Carolina mountains. Rainfall will be light with only a trace to a few hundreths of an inch of accumulation expected across portions of the North Carolina mountains. A few isolated locations in the northern North Carolina mountains may see up to a tenth of an inch of rainfall. Surface high pressure gradually builds in from the north the rest of the day Saturday allowing dry conditions to return across the mountains and keeping dry conditions in place east of the mountains. Lows Saturday night will be ~20 degrees above normal. Highs Saturday will be ~20- 25 degrees above normal thanks to afternoon temps climbing back into the 70s east of the mountains and across the mountain valleys.

Key Message #2: Weak cold air damming develops Saturday night into Sunday leading to cooler, but still above normal highs on Sunday.

The aforementioned surface high will continue building into the region from the north Saturday night into Sunday morning before the center pushes off the Mid-Atlantic/Southeast Coast Sunday evening. This will allow weak cold air damming to develop Saturday night into Sunday with spotty light drizzle and/or rain possible, but confidence is low as most of the 12Z CAMs and the latest NBM keep mostly dry conditions around. Lows Saturday night will remain ~20 degrees above normal. Although highs on Sunday will be cooler, they will still end up ~5-10 degrees above normal.

LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/

As of 1200 PM EST Christmas Day...

Key Message #1: A cold front brings rain on Monday with above normal highs lingering ahead of the front. Behind the front, brief, light northwest flow snow may develop Monday afternoon into Monday evening.

Upper ridging pushes east and deamplifies as a trough approaches out of the west Sunday evening into Monday. At the surface, a cold front approaches out of the west Sunday evening into Sunday night before tracking across the forecast area Monday morning into Monday afternoon. This will bring rain chances back to the forecast area on Monday with a brief shot of northwest flow snow developing behind the front Monday evening into Monday night, mainly along the NC/TN border. Very little snowfall accumulation, if any, is expected at this time. Rainfall amounts will generally be light as well, with most locations east of the mountains lucky to get a trace to a few hundreths of an inch of rainfall. Higher amounts ranging from a tenth of an inch to a quarter of an inch are expected across the mountains. Locally higher amounts up to half an inch should remain confined to the NC/TN border counties. Lows Sunday night will end up ~25 degrees above normal. Highs will be cooler across the mountains on Monday but warmer east of the mountains, ending up ~10-15 degrees above normal.

Key Message #2: Gusty winds develop ahead of/behind the front Sunday night into Monday night, lingering across the mountains on Tuesday while gradually decreasing in speed. The northern North Carolina mountains should see gusty winds linger through the end of the period.

Gusty southwest winds will develop ahead of the front Sunday night but will remain below advisory criteria. Winds will gradually turn northwest behind the front throughout Monday, with wind speeds gradually increasing through the afternoon (east of the mountains and evening (across the mountains) hours. Avery County as well as elevations above 3,500 feet in Mitchell, Yancey, and Buncombe Counties could see gusts reach advisory criteria so a Wind Advisory may be needed for these locations. Wind gusts elsewhere appear to remain below advisory criteria for now. Will continue to monitor forecast trends closely in the coming days. Gusty winds should linger across the northern North Carolina mountains through the end of the period, but will remain well below advisory criteria.

Key Message #3: Drier conditions and colder temperatures return Monday night into Thursday. Gusty winds combined with cold temperatures will lead to cold wind chills Monday night into Tuesday morning, mainly across the mountains.

High pressure builds in from the west/southwest behind the departing front Monday night into Tuesday, lingering over the region through Thursday. This will allow dry conditions and colder temperatures to return to the forecast area. Gusty winds will linger over the mountains on Tuesday, but will gradually decrease in speed. Gusty winds combined with colder temperatures Monday night into Tuesday morning will lead to cold wind chills across mainly the North Carolina mountains. Wind chills across the mountains will range from the single digits to the teens for most locations, although higher elevations across the northern North Carolina mountains will see below zero wind chills. For now it appears that wind chills will remain above Cold Weather Advisory criteria. Temperatures are generally expected to range from near normal to below normal Monday night through Thursday.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

At KCLT and elsewhere: VFR conditions to start with restrictions entering overnight and into Friday morning. Winds continue to diminish through this evening. Very low-end gusts are possible at KCLT through 23z so will keep a g15kt. Wind direction toggles almost a full circle through the TAF period. Mainly W/NW to start, becoming VRB this evening and picking up out of the NE/E after midnight. By Friday, winds become more E/SE and almost S at KCLT. Cloud cover increases from the northeast overnight and drops cigs into the MVFR/IFR range for Friday morning. KHKY and KAVL could also have some vsby restrictions for BR in the early hours. For this, a TEMPO at KAVL for 1SM from 12z-15z. These restrictions are expected to remain in place through the end of the TAF period.

Outlook: VFR returns Saturday with restrictions possible into Sunday as a front comes into the area.

CLIMATE

RECORDS FOR 12-25

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 71 2021 14 1983 59 2015 -7 1983 KCLT 77 1955 22 1983 63 2015 4 1983 KGSP 78 1955 22 1983 61 2015 6 1983

RECORDS FOR 12-26

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 78 1971 17 1902 55 2015 0 1983 KCLT 77 2021 27 1983 58 2015 6 1983 1964 KGSP 76 2021 28 1983 62 1987 5 1985 2015 1980

RECORDS FOR 12-27

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 72 1971 19 1902 59 2015 3 1925 KCLT 72 2021 22 1892 65 2015 15 1970 2015 1948 1971 1925 KGSP 75 1971 29 1925 64 2015 12 1925

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...None. SC...None.