textproduct: Greenville-Spartanburg

SYNOPSIS

An upper level disturbance arrives late tonight and brings the potential for light precipitation through Monday. Expect a dry and chilly Tuesday. Near normal temperatures return Wednesday ahead of a cold front which arrives late in the week. Expect chances of precipitation ahead of the cold front then much cooler temperatures by the end of next weekend.

NEAR TERM /THROUGH MONDAY/

As of 1000 PM EST Sunday...

Key Message 1: Dense Fog Advisory has been issued and expanded to include most of the NW Piedmont and Charlotte area thru 7 am Monday.

Dense fog has formed mainly along and east of I-77, and may continue to expand, as conditions look favorable. Have issued a Dense Fog Advisory for most of the NW Piedmont and the Charlotte area (Mecklenburg, Cabarrus, and Union). The advisory goes until 12z/7am, but visibilities may improve before then, as mid clouds thicken from the west and rain moves in right around daybreak Monday. The HRRR keep showing vsby tanking within the low stratus deck across most of the Upstate, as well. But confidence is too low to expand the advisory.

Key Message 2: Winter Weather Advisory remains in effect for Avery County as well as elevations above 3,500 feet in Yancey and Mitchell Counties from 1 AM Monday to 1 AM Tuesday. A cold rain is expected elsewhere.

The upper trough will push across the forecast area as the sfc high weakens in response to a weak surface wave tracking across the forecast area overnight into Monday. This will allow precipitation chances to return from west to east early Monday morning. With temperatures expected to fall near or below freezing above 3,500 feet in the North Carolina mountains, snow can be expected overnight into Monday. Snow accumulations should range from 2 to 3.5 inches above 3,500 feet across the northern mountains with locally higher amounts up to 4 inches possible across the highest peaks. Thus, the Winter Weather Advisory remains in effect for Avery County as well as elevations above 3,500 ft in Yancey and Mitchell Counties from 1 AM Monday to 1 AM Tuesday. The mountain valleys in Mitchell and Yancey Counties could see anywhere from a dusting to an inch of snowfall Monday morning into Monday afternoon. Elevations above 3,500 ft in the southern North Carolina mountains will see below advisory criteria snowfall from a few tenths of an inch up to 1.5 inches. However, locations in the Smokies along the NC/TN border could see totals from 1 to 2 inches with locally higher amounts in isolated locations.

Temperatures should remain above freezing across the rest of the mountain valleys and areas east of the mountains so mainly a cold rain can be expected for these locations. However, some light snow may blow down the valleys and/or some wet-bulbing may occur east of the mountains (mainly in the North Carolina foothills/Piedmont along and north of I-40) which could allow some brief snow to mix in with rain at times. It's not entirely out of the question for wet-bulbing to occur south of I-40 in the North Carolina foothills/Piedmont as some of the CAMs and global guidance depict this scenario. However, with the cold air chasing the moisture east of the mountains confidence on snow making it that far south remains very low at this time. No significant snowfall accums are expected east of the mountains if wet-bulbing does occur so opted not to issue a Winter Weather Advisory at this time as any snow that falls will be well below advisory criteria (less than an inch). With cloud cover lingering through daybreak Monday, lows will end up a few degrees above normal. Highs Monday will be cooler thanks to both cloud cover and precip, ending up ~10-15 degrees below normal.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/

Key Messages:

1) Light snow tapers off Monday night into Tuesday morning.

2) Breezy winds on Wednesday, especially over the mountains.

As of 1205 PM EST Sunday: Monday night, the departing shortwave and lingering snowfall should taper off throughout the night. Though the bulk of snowfall is expected, cannot rule out a few bursts of flakes still occurring east of the mountains, especially in the NC Piedmont. The colder air keeps snow probabilities in this area around 10-20% through Tuesday morning. Once the winter mix tapers off, Guidance also continues to signal increased wind speeds the high pressure keeps the weather quiet through the remainder of the period. Meanwhile, a strong area of low pressure churns over Canada and dips southward, creating a tighter pressure gradient closer to the CWA. Currently, there is about a 30-40% chance of wind gusts greater than 35 mph at the higher elevations of the mountains. This will likely change depending on how far south the low dips. If it drops further south, the winds are likely to increase. At this time, winds remain well below any Wind Advisory criteria. Temperatures on Tuesday remain below normal before rebounding to near normal on Wednesday.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Key Messages

1) Low confidence in precip associated with a cold front that moves through late in the week.

2) A potential colder period next weekend with temperatures running around 15 degrees below normal.

As of 1215 PM EST Sunday: Picking up on Wednesday night, an area of low pressure churns across the Great Lakes region, bringing a tight pressure gradient southward toward the region. Guidance has trended even drier in terms of precip, so a spotty PoP of 15-20% through Thursday morning over the mountains. Any gusty winds also look to diminish by Thursday. The next system lines up for the end of the week and into the weekend as a strengthening trough sets up over the eastern CONUS and brings NW flow aloft. This is a typical deep winter pattern occurring much earlier in the season, which can signal for a potential NW snow event over the mountains. However, a lot can and will change from now through the potential event. Guidance has been trending drier as the strong cP airmass breaks containment from the north and plunges into the central and eastern CONUS. The potential cold front is likely to increase precipitation chances, but will depend on how much moisture is retained once the cold, dry air arrives. So far, guidance is trending more toward a drier front with reduced precip chances. It remains too far out on the horizon to gather much of the details. As for temperatures, expect daily highs to be near normal until the frontal boundary comes through, dipping temps well below normal for the weekend.

AVIATION /03Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: IFR cigs nver completely cleared out across much of the Upstate and southern NC Piedmont. In general, these clouds are expected to expand again, with areas of fog possible, as well, especially where skies managed to clear out. Not expecting as widespread of LIFR/VLIFR as last night, but still could see 1/2sm or lower VSBY and/or 100-200 ft cigs. Conditions may actually improve slightly in the 10-12z time frame, as an area of light to moderate rain moves in from the west and scatters out some of the fog. Winds also expected to pick up out of the NE Monday morning. From there, guidance shows back edge of precip may change over to a mix of RA/SN or all SN in the NW Piedmont of NC. Confidence is high enough to add a PROB30 to KHKY for late morning to early aftn. Some guidance even has a changeover as far south as KCLT. Even if this does happen, it would be occurring around midday with temps in the upper 30s to lower 40s. So risk of impacts is low, but not zero. Precip should taper off by late aftn outside the mountains. There is some disagreement on how much cigs improve. For now, will bump up cigs to low-MVFR. However, IFR conditions may linger into Monday evening across most of the area.

Outlook: Restrictions should linger through Monday night. Dry high pressure returns Tuesday into Wednesday. NW flow precip may develop along the NC/TN border Wednesday night into Thursday but dry conditions should linger elsewhere.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Winter Weather Advisory until 1 AM EST Tuesday for NCZ033-049- 050. Dense Fog Advisory until 7 AM EST Monday for NCZ035>037-056- 057-069-071-072-082. SC...None.