textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The aviation forecast was updated to reflect the recent 00Z TAF issuance.

The Flood Watch for most of western North Carolina has been allowed to expire.

KEY MESSAGES

1. We are now past the highest threat of heavy rainfall, but some level of locally excessive rainfall potential continues through Saturday. The Flood Watch for western North Carolina will expire at 8 PM LT, with no plans for expansion into the Upstate. 2. A return to typical mid-summer weather begins Sunday and continues through at least Thursday, with hot temperatures and mostly isolated diurnal convection expected.

DISCUSSION

Key message 1: We are now past the highest threat of heavy rainfall, but some level of locally excessive rainfall potential continues through Saturday. The Flood Watch for western North Carolina will expire at 8 PM LT, with no plans for expansion into the Upstate.

1021mb sfc high continues settling southward into the upper Mid-Atlantic, and driving a more stable air mass into the northern reaches of the forecast area this evening. Widespread showers and embedded thunder continue across much of the area, but the axis of heavier rainfall rates has shifted south following the leading edge of a stalled frontal boundary. Consequently, the most impactful weather appears to be over for North Carolina, and the Flood Watch will be allowed to expire on schedule at 8 PM / 00Z.

Although surface-based stable air is expected across much of the area on Friday, some elevated instability is expected across much of the southwest half...while some ripples aloft are expected to pass over the area throughout the day. Scattered showers and some storms are expected to redevelop by afternoon, with likely PoPs advertised across much of this area. While the potential for isolated excessive rainfall will be lower, a marginal risk will exist...with perhaps a slightly higher risk across the southwest fringe, where the highest muCAPE is expected. Slightly more unstable conditions are possible Saturday, albeit with generally lower moisture content. Nevertheless, scattered showers and some TS are again expected during the afternoon, with a continued low end heavy rainfall threat.

Forecast high temps are around 10 degrees below climo across much of the CWA Friday, except for warmer conditions across the southwest fringe. Saturday will be warmer, but still below normal across most of the area.

Key message 2: A return to typical mid-summer weather begins Sunday and continues through at least Thursday, with hot temperatures and mostly isolated diurnal convection expected.

A drier and hotter pattern is forecast to evolve by the end of the weekend, as the axis of a long wave trough pushes just off the East Coast, with rising heights expected across our area through much of the week as a ridge builds strongly across the Rockies and Great Plains. Temperatures warm to normal by Monday, and perhaps a little above climo by mid-week. A return to a diurnal convective cycle is expected, with said cycle currently expected to be relatively inactive, as (at most) isolated activity is forecast each afternoon/evening.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: Expect tonight to be about as clear as peanut butter, or maybe pea soup. Widespread SHRA with embedded TS is still ongoing across most of the terminal forecast area, as a stalled frontal boundary slowly sags south into South Carolina. Already seeing MVFR to IFR ceilings and highly-variable visibility at most of the TAF sites (with the exception of KAND, which has thus far managed to remain VFR, but should begin to deteriorate soon as showers and storms reach the southern portions of the Upstate). Expect SHRA/TSRA to linger through late evening, before steadily tapering off toward and after midnight. For the Upstate sites, VCSH is warranted all night long, while for the mountain and Piedmont sites, there should be a period of entirely dry conditions beginning by about 2-3AM LT. However, widespread IFR to LIFR ceilings and lowered visibility will persist the entire night at all terminals. We'll likely see much of the area stay socked into IFR conditions through at least mid-morning, before some improvement can finally be expected. Some of the high-res guidance actually depicts another round of light showers around and after daybreak over the Upstate, but confidence is limited. Another round of convection should begin by early afternoon Friday. Some models suggest this activity may remain more confined to the Upstate (generally in the vicinity of the stalled boundary) but again, confidence isn't great, and PROB30s were warranted everywhere to account for this.

Outlook: At least IFR restrictions appear likely again Friday night, and convection will redevelop on Saturday. As the front finally settles south, some drying is in order for Sunday and Monday, so convective chances and restrictions look less likely. Low stratus and/or fog will be possible each morning in mountain valleys and any locations which receive heavy rainfall by day.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Flood Watch until 8 PM EDT this evening for NCZ036-037-048>053- 056>059-062>065-068>072-503>510. SC...None.