textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The forecast continues to trend wetter and cooler late this week through the weekend.

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

KEY MESSAGES

1. A cold front will approach the area tomorrow and then stall nearby through the weekend bringing a cooler and wetter forecast.

DISCUSSION

Key message 1: A cold front will approach the area tomorrow and then stall nearby through the weekend bringing a cooler and wetter forecast.

The synoptic pattern currently features upper ridging extending along the east coast with an upper low associated with a Tropical Upper Tropospheric Trough (TUTT) just off the southeast coast. Farther upstream, broad troughing extends from the west coast through the Mississippi Valley with a plethora as embedded waves and impulses. A surface cold front is also draped along the Ohio Valley and is slowly making its way southeast towards the Appalachians. Heading into tomorrow, the upper ridge will begin to break down and shift offshore with at least some degree of weak moisture return continuing into the Carolinas. At least one more hot day is expected on Wednesday with upper 80s to low 90s common. As the cold front pushes into Tennessee, a few isolated to widely scattered showers and storms will be possible across the mountains. While some timing uncertainty remains, guidance is in generally good agreement that the front will push into the area on Thursday with greater coverage of afternoon showers and thunderstorms.

By Friday into the weekend, a sprawling surface high slides out of the Great Lakes and into New England and southeast Canada. This allow for at least a weak cold air damming wedge to set up shop and persist perhaps through the weekend and into the start of next week. By this time, deep layer southwest flow is progged to reside from the Gulf Coast into the Mid-Atlantic with several embedded perturbations. Associated moisture and bouts of forcing combined with ascent atop the wedge boundary is expected to keep a noticeably wetter and cooler pattern in place for at least several days. This will feature highs in the mid 70s to low 80s with daily rain chances. No organized severe weather threat or flooding threat is apparent at this time, just a beneficial rain that will at a very minimum help keep the drought from getting worse.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

At KCLT and elsewhere: VFR conditions expected to continue at all terminals through the period. An area of thick cirrus will persist over the mountains and western Upstate, but should thin out by daybreak Wednesday. A little more low-level moisture will work in from the southwest ahead of an approaching cold front. This should produce a few to scattered Cu field across most of the area, with thickest clouds over the mountains. Isolated to widely scattered SHRA and TSRA expected in the mountains, mostly near the TN border. But there is about a 30 percent chance convection makes it to KAVL, so will add a PROB30 for early tomorrow evening. Otherwise, winds will be generally light and out of the southwest.

Outlook: An approaching front and increasing moisture will bring a more active pattern for mainly afternoon and evening showers and thunderstorms beginning Thursday afternoon and then continuing through the end of the week. Cold-air damming may produce widespread MVFR to IFR cigs thru the day Friday. The potential for overnight fog/low clouds will increase through the period as well.

GSP WATCHES/WARNINGS/ADVISORIES

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