textproduct: Greenville-Spartanburg

SYNOPSIS

Cool high pressure remains over the area through the weekend. A strong cold front aims to sweep across the area early Sunday, bringing very cold temperatures to start the week. Dry conditions and temperatures rebound by mid next week.

NEAR TERM /THROUGH TONIGHT/

As of 1220 AM EST Friday...

Key Message #1: Cold start this morning with light snow lingering through daybreak along the North Carolina/Tennessee border. Light snow may break containment of the mountains, with light snow or flurries possible across the northern North Carolina foothills. Snow accumulation will be very light, if any.

A clipper low will continue tracking southeastward through daybreak, with the bulk of precipitation associated with the low remaining north of the GSP forecast area. However, the southern portion of the low will clip the northern and western tier of the forecast area through daybreak. This will allow light snow/flurries to continue along the NC/TN border counties and possibly even the northern North Carolina foothills. With activity expected to remain light, very little accumulation (if any) is expected. Temperatures will fall into the lower to upper 20s across the mountains, with the upper 20s to lower 30s expected east of the mountains. This will lead to lows ending up near normal to just below normal.

Key Message #2: Although dry conditions are expected across much of the area today, light snow/snow flurries should linger across the extreme northern tier of the forecast area through early this afternoon, with some areas seeing a transition to rain as temperatures warm.

Cyclonic flow remains aloft through the period while the clipper low gradually dissipates north of the forecast area this afternoon and evening. This will allow light snow/flurries to linger through the late morning/early afternoon hours across the extreme northern tier of the forecast area before dry conditions return the rest of the period. May see snow gradually transition to rain across the northern North Carolina foothills and Piedmont as temperatures warm and if precip lingers long enough. Dry conditions will continue elsewhere across the forecast area through the near term.

Key Message #3: Trending Warmer through the near term with cloud cover gradually thinning out later this morning into this afternoon.

As an upper shortwave embedded within the cyclonic flow lifts north and east of the forecast area this afternoon/evening, allowing cloud cover to gradually thin out. With low-level surface flow gradually turning S/SW, highs today will end up several degrees warmer across much of the forecast area, although the North Carolina Piedmont and foothills will see similar highs compared to yesterday. However, temperatures will still end up below normal across much of western North Carolina and the eastern South Carolina Upstate. Temperatures will end up a few degrees above normal across the western South Carolina Upstate and northeast Georgia (where cloud cover will generally be thinner). Lows tonight will range from the upper 20s to mid 30s, ending up a few degrees above normal across the mountains and near normal to just below normal east of the mountains.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

As of 1220 AM EST Friday:

Key Message 1: Brief warm up Saturday and dry conditions expected.

Main synoptic pattern shifts as a strong upper low over the Great Lakes ushers a frigid Arctic air mass into the central CONUS. Surface high pressure lingers across the southeast and slowly slides off shore, keeping the area dry on Saturday. Guidance keeps SW surface winds with a shallow layer of moisture reaching the area, but no precipitation is anticipated. With the height rises ahead of the cold air mass, temperatures look to reach the upper 50s and even low 60s in the southern areas.

Key Message 2: Increased chances for precipitation Saturday night ahead of an Arctic front.

Aloft, the upper low swings southward and increases precip chances. The surface moisture lingering ahead of the front should provide a narrow window for precipitation east of the mountains and a brief burst of snow at the higher elevations. At this point, confidence is low on how much precip can occur as it's highly dependent on the lingering moisture lining up with the better forcing ahead of the Arctic front. Keeping slight chance PoP (15-30%) for most of the area. Any precip, whether it be rain or snow, looks to be very low. The chance for receiving more than 0.01" of rainfall is about 25- 30%, with the higher chances across the mountains. As for any snow, there's about 20-40% chance of 0.1" or more accumulating along the TN/NC border. Basically, the brief window for moisture lining up with the colder air produces flurries at best.

Key Message 3: Gusty winds with cold temperatures move in Sunday into Sunday night.

The Arctic air mass spills into the area Sunday and Sunday night, bringing strong wind gusts over the mountains and elevated winds gusts east of the mountains. A this time, winds gusts over 40 mph have a great chance (50-60%) of occurring at the highest peaks with the remainder of the mountain areas looking to reach the 30-39 mph wind gusts for Sunday. Current guidance has these wind gusts diminishing quickly Sunday night. Additionally, these winds usher in the coldest air of the season. Confidence is increasing that the entire area drops into the mid to lower teens east of the mountains and single digits in the mountains. With the added wind gusts, temperatures will feel even colder, as values dip below zero at the higher elevations Sunday night. Confidence is also increasing that these cold and windy conditions could prompt the issuance of a Wind Advisory and/or Cold Weather Advisory for portions of the area.

LONG TERM /MONDAY THROUGH THURSDAY/

As of 1230 AM EST Friday:

1) Cold air quickly exits the area with temperatures rebounding by mid-week.

By Monday morning, air temperatures are likely to remain well below freezing and slowly warm up through the day. Most of the area should rise above freezing for the daytime highs. At some point on Monday, the surface winds turn SW, helping to modify the Arctic air mass. As the high pressure strengthens offshore, temperatures increase with the ongoing height rises. Tuesday and onward to around normal by the end of the forecast period.

2) Surface high pressure keeps precipitation chances away with a slight chance of return by the end of the week.

High pressure remains overhead and suppresses precipitation chances through most of the week. Aloft, nearly zonal flow across most of the CONUS, reinforcing the quieter weather ahead. There is a slight chance (20-40%) of precipitation returning at the end of Day 7, however, model guidance differs this far out. Confidence in rainfall is low at this time given the uncertainty of where the western fringe of the surface high sets up. If it's further west, rain chances decrease and if it migrates further east, rain chances increase. But, the main precip type should anything occur, would be leaning more toward rain as temperatures are not supportive of snowfall for the majority of the area.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: VFR and dry across the terminals through the period. Cannot entirely rule out some isolated snow flurries blowing down the valley at KAVL prior to daybreak. SCT to BKN cloud cover will continue through the late morning hours before gradually thinning out this afternoon and evening. Winds will generally be calm to light and VRB through the early morning hours before picking up out of the SE by mid-morning. Winds will gradually turn more S/SW late this morning into early this afternoon. Winds should flip N by the early evening hours, with the exception of KAND which should remain W/WSW through the end of the 06Z TAF period.

Outlook: Another clipper system could bring lower clouds and precip into the area Saturday night into Sunday, along with gusty winds and much colder temperatures. Robust, dry high pressure settles into the area late Sunday into Monday before sliding east Tuesday.

GSP WATCHES/WARNINGS/ADVISORIES

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