textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated PoP trends this morning based on radar and latest high resolution guidance.

Updated for the 12Z TAFs.

KEY MESSAGES

1. Showers and storms early this morning give way to sunny skies by afternoon. Dry and cooler tonight. 2. The next weather-making disturbance will track along the Gulf Coast and into the western Atlantic on Friday and Saturday, bringing a round of beneficial rainfall to the western Carolinas through Saturday afternoon. 3. Dry and quiet weather will persist from Sunday through the middle of next week. Another cold front may approach the area by late next week, but forecast predictability is low at this time.

DISCUSSION

Key message 1: Showers and storms early this morning give way to sunny skies by afternoon. Dry and cooler tonight.

A line of storms, a few strong with very gusty winds, and a trailing area of showers will move east of the area by mid morning. Sunny skies developing in the wake of the showers. Winds remain gusty across the mountains through the day before tapering off overnight. Some low end gusts are possible outside of the mountains as well. Highs a little below normal across the mountains and near normal elsewhere. Clouds return overnight with lows around 5 degrees below normal.

Key message 2: The next weather-making disturbance will track along the Gulf Coast and into the western Atlantic on Friday and Saturday, bringing a round of beneficial rainfall to the western Carolinas through Saturday afternoon.

Still expect surface wave traveling along a baroclinic zone near the Gulf Coast to incite moist upglide over the forecast area beginning late Friday...resulting in widespread drizzle and rainfall across the area from Friday night through the first part of Saturday. By early Saturday afternoon, the upper reflection will incite surface cyclogenesis near Cape Hatteras, choking off moisture as CAA develops on the backside of the low and bringing an end to precipitation by Saturday evening.

Long-range ensembles are in excellent agreement that with the warm front well to our south, no surface-based instability will be able to develop, so any embedded thunder will be elevated in nature, and severe risk will be virtually nil. QPF remains a question mark, with the latest NBM supporting nearly an inch south of I-85, and barely 0.25" north of I-40. However, there remains quite a bit of spread in ensemble guidance, with a solid third of the 12z LREF membership depicting a significantly weaker baroclinic circulation than the operational guidance, and therefore weaker upglide producing lower QPF (to the tune of barely more than half the totals currently supported by the NBM and 00z operational guidance, and depicted in the official forecast). Only over the next 24 hours as the REFS and HREF begin to capture this event in its entirety, will confidence on rainfall totals begin to increase.

Key message 3: Dry and quiet weather will persist from Sunday through the middle of next week. Another cold front may approach the area by late next week, but forecast predictability is low at this time.

High pressure will dominate the forecast through the end of the weekend and beginning of the new workweek. Beneath quasi-zonal flow aloft, a postfrontal air mass will migrate from the Deep South on Sunday into the western Atlantic by Monday night and Tuesday, allowing Gulf moisture to only slowly advect back into the area through the middle of next week.

As is typical under such regimes, we'll initially see temperatures some 10 degrees below normal in the initial postfrontal air mass on Sunday...but the air mass will quickly modify, and we can expect highs to climb back above normal by Tuesday, reaching their apex on Wednesday when they're expected to hit the mid-80s again. Also, despite surface dewpoints slowly recovering through mid-week, forecast profiles depict a deep dry slot aloft...so daytime mixing should permit at least isolated near-critical RHs to develop each afternoon. They don't currently look to fall low enough to warrant widespread fire wx concerns - espeically since, after multiple rounds of rainfall, fuels across the area should be somewhat less primed for ignition - but we'll nonetheless need to monitor conditions and confer with land managers on the state of things once we get past the Fri/Sat system.

By the end of the seven-day forecast period, guidance completely loses anything resembling consistency, broadly depicting an amplifying upper trough over the central CONUS, but failing to come to any consensus on when it'll drive any active weather back into the Carolinas. To wit, some ensemble runs bring a cold front back into the area as early as Wednesday afternoon; other runs keep any frontal zone well to our west until well after D7. If nothing else, it appears reasonably likely that the amplified pattern will continue...so more rain is at least somewhere on the horizon.

AVIATION /12Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: A line of storms with a trailing area of showers will move out of the area by 14Z or so. Until then, expect MVFR conditions, possibly briefly IFR, and variably gusty winds. Once the showers move east, expect clearing skies and lighter NE wind for most. Gusty NNW wind will continue through the day at KAVL. KAND will see a westerly afternoon wind. Winds go light N to NE during the evening into the overnight with increasing mid and high clouds.

Outlook: Dry and VFR Friday before another disturbance brings rain chances and associated restrictions Friday evening into Saturday. Dry and VFR conditions return Sunday and linger through at least Tuesday.

GSP WATCHES/WARNINGS/ADVISORIES

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