textproduct: Greenville-Spartanburg

SYNOPSIS

Cool high pressure moves in through Sunday before precipitation chances increase late Sunday night and Monday. Dry conditions return by midweek with normal temperatures. A cold front should arrive late in the week.

NEAR TERM /THROUGH SUNDAY/

As of 630 PM EST Saturday...

Key Message 1: Seasonably chilly with possible widespread dense fog east of the mountains tonight through mid-morning Sunday.

Dry high pressure will continue building into the region while an upper trough pushes east of the western Carolinas and northeast Georgia by late this evening. This will allow calm winds to develop overnight. Cloud cover will gradually increase this evening into tonight, especially east of the mountains. Despite the cloud cover, it will be a cold night with temps falling near to below freezing across the entire forecast area. Another round of dense fog will develop tonight into daybreak Monday thanks to the calm winds and lingering low-level moisture. Freezing fog looks to develop across the NC foothills and the NC Piedmont (north of I-85) overnight into early Sunday morning as these are the areas that are most likely to see dense fog overlap with freezing temperatures.

Key Message 2: Fog lifts by mid-morning Sunday with dry and warmer (but still below normal) conditions expected as cloud cover sticks around.

Dense fog will linger through the early morning hours on Sunday before gradually lifting by mid-morning. Freezing fog across the NC foothills and the NC Piedmont (north of I-85) will no longer be a concern once temps rise above freezing. The sfc high will be overhead the Carolinas on Sunday allowing drier and warmer conditions to develop. However, highs will still end up ~4-7 degrees below normal thanks to cloud cover sticking around. Temps Sunday afternoon will reach into the upper 40s to mid 50s east of the mountains and across the mountain valleys. Higher elevations will see highs range from the lower to mid 40s.

SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/

Key Messages:

1) Light snow possible across portions of the mountains Sunday night into Monday, with cold rain elsewhere.

2) Dry conditions return Tuesday with below normal temperatures.

As of 1205 PM EST Saturday: West of the CWA, a shortwave makes a run for the area Sunday night into Monday, bringing another chance for precipitation. Guidance shows colder air to the north working its way down into the southeast from a weak surface high. Guidance is divided on precip except for the GFS, which paints a wider swath of precip. One factor limiting this system is forcing. There isn't much across the area and even the better DPVA is further south. Without the forcing component, rain chances look to be lower. Additionally, colder air looks to arrive in the mountains in time for the shortwave to come through. However, should the shortwave slow down, this could increase the probability of some snow, mainly across the mountains. Currently, there is about a 70-80% chance that the highest elevations in the mountains could see at least 0.01 inch of snow. There is also about a 20-30% chance for a few isolated areas at the higher spots to see 2 inches of snow or more. Timing for this is late Sunday night into Monday, but this is still a developing system and things will change. Outside the mountains, the colder air doesn't look to arrive in time for the shortwave to cross, keeping temps mostly above freezing and precip type as mainly rain. There could be a brief mix of snow outside the mountains, especially in the NC Piedmont IF the cold air makes it in time AND the wet bulb cools to near/at freezing. Cannot rule it out, but accumulations are not expected at this time outside the mountains. Confidence in this system remains medium that the mountains could see 0.01-2 inches of snow, which is again highly dependent on the timing of the colder air and shortwave. Will continue to monitor. After the colder air mass arrives, a weak surface high sets up, keeping the CWA dry on Tuesday. Due to anticipated NE surface winds, temperatures look to dip well below normal Monday and Tuesday.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Key Messages:

1) Quiet through mid-week with a warming trend back to normal temperatures.

2) Breezy Wednesday, especially across the mountains.

3) A potential cold front late Thursday or Friday could bring cooler temps and another chance of precipitation.

As of 1210 PM EST Saturday: From Tuesday night through at least Thursday, the weather remains quieter. By midweek, a strong area of low pressure churns across the Great Lakes region, bringing a tight pressure gradient southward toward the region. A brief increase of PoP chances (15-30%) over the mountains Wednesday night. Additionally, guidance has wind speeds increasing Wednesday into Wednesday night. A this time, there is about a 30-40% chance of wind gusts greater than 30 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. Toward the Thursday/Friday timeframe, there is a continued hint in guidance of another potential cold front with precipitation chances increasing. Current guidance brings this front in much drier than previous runs and signals at much colder temperatures. So far, guidance is trending more toward a drier front with reduced precip chances. Again, it's too far out on the horizon to gather much of the details. As for temperatures, expect daily highs to be near normal from mid-week onward.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: VFR conditions have returned to all TAF sites at time of 00z TAF issuance, but will not last long. Low cigs and dense fog will quickly develop this evening into early Sunday morning across the Piedmont. The mountain valleys may see some fog as well, but guidance is not showing much there. Will introduce a TEMPO at KAVL for some IFR cigs/vsby around daybreak. The set up looks good for widespread fog development for the Piedmont overnight thru late morning Sunday. The fog/low stratus should gradually lift late morning to early aftn, but confdience remains low to modearte on whether all sites will return to VFR before sunset Sunday evening. Some areas may possibly not scatter out completely before conditions support MVFR to IFR cigs returning Sunday evening. Temps are expected to dip below freezing at KHKY, so will continue to TEMPO some FZFG. TEMPOs for dense fog (below airport minimums) will be added to the other Piedmont sites in the 10-14z time frame. Wind will be calm or LGT/VRB thru most of the period. May favor a S to SW direction by Sunday aftn.

Outlook: A storm system will bring precip and restrictions Sunday night into Monday. Dry high pressure is expected to spread back over the area Tuesday into Wednesday.

GSP WATCHES/WARNINGS/ADVISORIES

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