textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The aviation discussion has been updated for the 12Z issuance of the TAFs.

KEY MESSAGES

1. Dry and quiet through at least Friday. Near to just below normal highs develop briefly today before above normal highs return for the rest of the workweek. 2. A more active pattern brings rain chances back this weekend, potentially lingering into early next week. Confidence on timing and details remains low at this time.

DISCUSSION

Key message 1: Dry and quiet through at least Friday. Near to just below normal highs develop briefly today before above normal highs return for the rest of the workweek.

Troughing will be the dominant upper feature across the northern and eastern United States through Friday. At the surface, dry high pressure will be the main feature for the central and much of the eastern United States through at least Friday. Near to just below normal highs briefly develop today before above normal highs return for the rest of the workweek. Highs peak on Thursday, ending up around 10 degrees above normal.

Key message 2: A more active pattern brings rain chances back this weekend, potentially lingering into early next week. Confidence on timing and details remains low at this time.

The western periphery of an upper ridge over the western Atlantic builds northwestward towards the Southeast Friday night into Sunday before shifting south and west into the Gulf early next week. Meanwhile, an upper low attempts to develop somewhere over Texas before lifting northeast toward the Tennessee Valley/ Midwest over the weekend and the Northeast early next week. This will allow rich gulf moisture to stream into the Southeast over the weekend, of which there will be plenty thanks to a both a stationary boundary and a tropical disturbance creeping northward towards the Gulf Coast.

The tropical disturbance is currently located in the southwestern Gulf and will eventually lift northward sometime Friday or over the weekend while interacting with the stationary boundary. Per the NHC this disturbance is expected to develop into a Tropical Depression by mid-week, depicting the system as having a high chance of tropical formation through 48 hours. Global models are not in agreement regarding the strength, timing, or exact track of this system which is to be expected as the system currently remains a disorganized cluster of shower and thunderstorms. Guidance should come into better agreement once the system becomes more organized. For now, the disturbance appears to track northward and just west of the GSP forecast area. However, rain chances still look likely for locations east of the disturbance but confidence on exact arrival time and departure time of rain remains low. The GFS is the fastest solution, showing rain returning to the GSP forecast area by Saturday morning/early afternoon while the Canadian is the slowest solution with rain not arriving until Sunday afternoon/evening. The Euro is caught in the middle, showing rain arriving Saturday evening/night. The GFS has drier conditions returning by early next week due to it being the faster solution, while the Canadian and Euro have rain lingering through early next week with these two models being the slower solutions.

For now it looks like this system will bring mainly beneficial rain to the GSP forecast area. There is still plenty of time for the forecast to change between now and the weekend so make sure to stay up to date with the latest forecast information regarding this system.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: There are two areas of interest for aviation weather across the Terminal Forecast Area this morning...the first is the fog/low stratus covering much of the NC mountains. The worst of it hasn't quite made it to KAVL, but they recently reported 5SM/FEW002. Based upon trends in the latest derived satellite imagery and with sunrise looming, the worst conditions are likely to remain just beyond the airfield, but will carry a tempo for MVFR fog and SCT003 for the first hour.

The second area of interest is across the NC Piedmont, where a region of MVFR stratus is moving steadily toward KCLT from the east. Cigs aren't quite as low as some earlier guidance was suggesting they might be...but a tempo for MVFR still seems reasonable at KCLT from 13-16Z. All other sites should remain VFR, although can't rule out some MVFR cigs also making a run toward KHKY as the morning progresses. Having said that, there should be enough moisture trapped beneath a stable layer aloft to yield FEW/SCT stratocu/cumulus in the 020-040 range at most sites during the late morning into the afternoon, with cloud bases steadily lifting through the afternoon. NE winds are forecast to steadily increase to 8-12 kts through the morning before weakening again during the afternoon/evening. Fog/low stratus will return to the mountain valleys, with prevailing MVFR fog being a reasonable forecast at KAVL. All other TAF sites are likely to remain VFR through tonight.

Outlook: VFR conditions prevail through the end of the week. Mountain valley fog and low stratus are possible each night.

GSP WATCHES/WARNINGS/ADVISORIES

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