textproduct: Greenville-Spartanburg

SYNOPSIS

A backdoor cold front brings cooler temperatures and the chance of isolated light showers today before near-record high temperatures return on Saturday. Mild and dry conditions expected 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 SATURDAY/

As of 100 PM EST Friday...

Key Message #1: Weak cold air damming develops behind a back door cold front today leading to mostly cloudy skies, cooler (but still above normal) temperatures and light spotty rain.

Tricky temperatures forecast today as weak cold air damming develops behind a back door cold front. For now, it appears the front will push west of I-26 (stopping just short of northeast Georgia) before lifting back north-northeastward as a warm front this evening into tonight. This will keep mostly cloudy skies around area-wide as well as lead to a slight temperature and dewpoint gradient this afternoon and evening, mainly across the North Carolina Piedmont and Foothills. NBM appears to be handling temperature and dewpoint trends well so far today so no major changes were needed. Despite weak cold air damming, highs will still end up above normal. Highs will range from 5-7 degrees above normal across the North Carolina Piedmont and Foothills to 10-15 degrees above normal across the North Carolina mountains, South Carolina Upstate, and northeast Georgia. 12Z CAMs show the potential for some very light, spotty showers developing this afternoon within the wedge but confidence on this activity actually reaching the ground is low. Thus, capped PoPs to slight chance through this afternoon.

Key Message #2: Another back door cold front brings light northwest flow rain to mainly the NC/TN border counties as well as breezy winds above 3,500 feet this afternoon into tonight.

Another back door cold front approaches out of the north this afternoon into tonight, pushing across the mountains prior to daybreak Saturday. This will keep mostly cloudy skies around for the NC/TN border counties as well as bring light northwest flow rain to these areas. NBM chance PoPs appear to be in good shape along the NC/TN border. Light rain will taper off just prior to daybreak Saturday. Breezy winds will also develop ahead of and along the front above 3,500 feet in the North Carolina mountains this afternoon into tonight. Gusts will remain well below advisory criteria. Lows tonight will remain well above normal.

Key Message #3: Patchy fog may develop across portions of the forecast area tonight into Saturday morning but confidence is low.

Guidance shows the potential for patchy fog development overnight into early Saturday morning, mainly along/near I-77 as well as across the mountains where light northwest flow rain develops. Locally dense pockets of fog are possible at times but widespread dense fog is not expected at this time. Confidence on the fog potential is low as guidance has not been consistent run to run.

Key Message #4: Mostly sunny and dry with near record highs and diminishing winds above 3,500 feet on Saturday.

The aforementioned back door cold front will continue sinking south/west across the forecast area throughout Saturday allowing cloud cover and breezy winds above 3,500 feet in the North Carolina mountains to gradually diminish behind it Saturday morning into early Saturday afternoon. Despite the front, near record highs will return across the forecast area as temperatures rebound into the lower to mid 70s east of the mountains. Could also see some lower 70s across the Little TN and French Broad mountain valleys. KGSP and KCLT will have the best potential to tie or break their record high Saturday afternoon.

SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/

As of 12:35 PM EST Friday...

Key Message #1: A weak back-door cold front brings cooler temperatures and spotty light rain chances on Sunday.

Cooler high pressure builds in from the north late Saturday night into Sunday. Cold-air damming features develop on Sunday but they will be brief, as the parent high to our north will move off the Atlantic Coast by Sunday evening. Nonetheless, there will be an increase in low-level moisture along with some weak isentropic lift over our area. This will increase cloud cover and may produce some spotty light rain. Any precip amounts should be minimal. Despite the CAD pattern, highs on Sunday will remain roughly 5 to 10 degrees above normal.

Key Message #2: Gusty winds develop ahead/behind the front Sunday night and persist over our area into Tuesday.

Gusty SW winds will develop ahead of the cold front Sunday night and gradually turn NW behind the front on Monday, with speeds increasing thru the day. The gusty winds continue across the mtns Monday night and into Tuesday, but diminish elsewhere. Winds could reach Advisory criteria above 3500 ft by Monday afternoon, so a Wind Advisory may be needed for these locations. Elsewhere, wind gusts appear to remain below Advisory criteria, however frequent gusts of 25 to 35 mph can be expected.

Key Message #3: A robust cold front will move through the area Monday afternoon/evening increasing rain chances outside the mountains and rain/snow chances over the higher elevations.

A robust upper shortwave morphs into an upper low over the Great Lakes on Monday, then lifts NE into Quebec late Monday into Tuesday. The associated upper trof axis will rotate over our area by the end of the period late Monday, pushing a cold front thru our CWA. There will be some increase in low-level moisture across our area ahead of the front, but nothing remarkable. This will increase precip chances across the mtns late Sunday night into Monday, and areas east of the mtns Monday morning into the afternoon. We're still expecting QPF amounts to be minimal across our area, with up to 0.25 inches across the mtns and 0.1 inches or less elsewhere. Precip quickly tapers off by Monday evening with a brief period of NW flow snow possible over the higher elevations. Potential snow amounts have been trending down- ward, with even the most favored locations currently expected to get no more than and inch.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

As of 12:55 PM EST Friday...

Key Message #1: Drier conditions and colder temperatures return Monday night and linger thru mid-week. Gusty winds combined with cold temperatures will produce low wind chill values Monday night into Tuesday morning, mainly across the higher elevations of the North Carolina mountains.

Dry sfc high pressure builds in from west behind the departing cold front Monday night into Tuesday, and lingers over the region thru mid-week. The gusty winds and cold temperatures Monday night and Tuesday morning are expected to produce wind chill values over the NC mtns from the single digits to the teens for most locations with elevations above 3500 ft likely to see below zero wind chills. If values trend any lower, a Cold Weather Advisory may be needed for portions of the mtns. Otherwise, winds will remain gusty over the mtns on Tuesday, especially the northern NC mtns. Gusts will taper off elsewhere by Tuesday afternoon. Temperatures will slowly rebound thru Thursday, yet still remain below climatology for most locations.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

At KCLT and elsewhere: Still dealing with a remnant low cloud restriction over the NC foothills and western Piedmont, mostly affecting KHKY and KCLT, though the latter was on the edge and should probably break out over the next hour or so. The southern edge of the low clouds was more or less the location of a weak backdoor cold front that is expected to either wash out or lift back north. Meanwhile, another cloud deck was moving in from the west, but the cloud bases were mostly VFR. Tricky low confidence situation overnight as the low cloud restriction will either persist and expand east of the mtns to encompass most of the rest of the terminals, or a vis restriction will develop in the early morning hours. Which will win out remains to be seen, but either way, restrictions are expected and may vary between LIFR and MVFR. A bit more WNW flow will develop at low levels after sunrise Saturday and should mix out the low clouds and fog through mid/late morning. The bulk of the time from midday onward should be VFR as drier air filters in from the NW.

Outlook: Restrictions return Saturday night into Sunday, lingering through Monday ahead of and along a cold front. Spotty light rain may develop Sunday but better rain chances return Monday ahead of the cold front. Dry and VFR conditions return behind the front by late Monday, lingering through the rest of the workweek.

CLIMATE

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.