textproduct: Greenville-Spartanburg

SYNOPSIS

High pressure keeps dry conditions over the area through tonight before a cold front brings precipitation chances back Thursday into Thursday night. Drier conditions return behind the front Friday into the weekend as high pressure builds in from the northwest.

NEAR TERM /THROUGH TONIGHT/

As of 1230 AM EDT Wednesday:

Key Message #1: Another warm day ahead with dry conditions persisting.

Mild weather remains in place through tonight ahead of a cold front into the next period. Surface high pressure slowly starts to migrate eastward off shore tonight in response to an area of low pressure developing across the central CONUS. No rain is anticipated with the subsidence aloft through tonight. Winds remain light and mostly out of the southwest for locations east of the mountains, gradually increasing surface moisture. Ahead of the next cold front and precip chances (next forecast period), clouds are expected to increase throughout the day. Temperatures today warm into the upper 50s with lows tonight staying above freezing in the mountains and lower 40s in the southern counties.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

As of 1230 AM Wednesday...

Key Message #1: Cold front brings precipitation and gusty winds Thursday into Thursday night.

An upper trough will approach out of the west/northwest Thursday into Thursday night while gradually developing a negative tilt. At the sfc, a cold front will approach out of the west through Thursday evening before tracking across the western Carolinas and northeast Georgia Thursday night, bringing precipitation chances and gusty winds.

In-situ cold air damming looks to develop as a surface high centered off the New England Coast slowly lifts northeast, allowing for an influx of moisture (from both the Gulf and Atlantic) to stream across the forecast area ahead of the cold front. This will allow rain chances to gradually increase throughout Thursday. Cold air damming will act to limit instability which is good considering we will have 50-60+ kts of deep layer shear available ahead of/along the front. So, despite the negatively tilted trough, the severe threat will remain low, if any. Cold air damming will also lead to cooler temperatures so blended in 20% of the NBM 10th percentile for highs on Thursday. This blend led to highs ending up ~5 degrees below normal across the North Carolina Foothills and the northern North Carolina Piedmont (where cold air damming is will be the strongest). Elsewhere, highs may end up near normal to just above normal. However, highs on Thursday may end cooler than this east of the mountains (as we typically see in cold air damming). Gusty winds will develop ahead of/behind the front Thursday into Thursday night. Most locations will gusts remain below advisory criteria. However, Avery County, along with elevations above 3,500 feet in Mitchell, Yancey, and Buncombe counties, may see gusts have the best chance to see advisory criteria gusts. Thus, a Wind Advisory may eventually be needed for these locations.

Rain associated with the actual frontal boundary will push across the forecast area Thursday evening into Thursday night. As temperatures fall near/below freezing across the NC/TN border counties late Thursday night into early Friday morning, rain will briefly transition to snow before precipitation ends around daybreak. Only light snow accumulation is expected, with only a dusting to a few tenths of an inch expected. Rainfall totals will generally range from half and inch to an inch across the forecast area, with locally higher amounts from 1.5 to 2 inches possible across the southern North Carolina mountains. No hydro concerns with this system at this time. Low temperatures Thursday night will end up ~10-15 degrees above normal thanks to cloud cover and precipitation limiting radiational cooling.

Key Message #2: Dry conditions return Friday but gusty winds linger through the evening hours before tapering off overnight.

The aforementioned upper trough swings across the forecast area on Friday as dry high pressure builds in behind the departing cold front. Gusty winds linger throughout the day Friday before gradually tapering off Friday evening into Friday night. Highs on Friday will end up a few degrees below normal across the mountains and a few degrees above normal across the mountains. Lows Friday night will be colder, ranging from the mid 20s to lower 30s, thanks to mostly clear skies and lighter winds leading to better radiational cooling conditions.

LONG TERM /SATURDAY THROUGH TUESDAY/

As of 1245 AM Wednesday:

Key Message #1: Mostly dry this weekend into early next week, although rain chances may return across the western half of the forecast area at times after Saturday.

Quasi-zonal flow develops aloft Saturday into Sunday before heights rise Monday into Tuesday in response to an upper ridge building over the Gulf Coast. At the surface, high pressure will be the dominate feature outside of a weak cold front tracking across the area on Sunday. Global model guidance sources remain at odds regarding the exact timing and coverage of rain Sunday into Tuesday so confidence on NBM chance PoPs remains low. For now, it still appears that the western half of the forecast area will have the best chance to see rain return. Above normal temperatures are expected through the period.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

At KCLT and elsewhere: VFR conditions prevail through the TAF period. High pressure remains in place. No vsby/cig restrictions are anticipated at this time. Light winds out of the SW remains outside the mountains. Winds go calm at a few sites overnight before picking up Wednesday morning. VRB comes back after sunset tonight. Increasing clouds ahead of a front through the period, but should remain close to SCT/BKN250.

Outlook: Showers and associated restrictions are expected Thursday into Friday, with VFR returning by Friday afternoon and persisting through the weekend.

GSP WATCHES/WARNINGS/ADVISORIES

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