textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Rain totals have trended slightly less for showers through tonight, especially east of the mountains.

KEY MESSAGES

1. Ahead of a cold front, a few showers and thunderstorms through tonight before drier air returns for Sunday. 2. A series of storm systems will bring several rounds of rain chances through next week. Confidence in timing and any severe potential remains low at this time.

DISCUSSION

Key message 1: Ahead of a cold front, a few showers and thunderstorms through tonight before drier air returns for Sunday.

A weak cold front pushes into the area tonight, triggering showers and a few thunderstorms ahead of it. Though rainfall totals are not too impressive, any amount is welcomed. The higher amounts are expected in the far western zones of the NC mountains, with shower activity spreading into NE Georgia and Upstate SC later this evening and into tonight. Expect up to 0.25", with a few locations receiving a tick more, depending on where storms actually setup. As for any thunderstorm chances, current guidance is not supportive of anything severe. A stout inverted-V sounding shows a lot of dry air in the boundary layer and weak flow from the surface upward. Minimal instability and meager lapse rates also contribute to poor chances for thunderstorms. However, a few rumbles of thunder are still possible if storms can build high enough. So, expect a few showers to casually drift by and rustle up the winds briefly, before dry air returns for Sunday. The FROPA is expected to be so weak that it has almost no effect on the temperatures for Sunday. Widespread upper 70s for the mountains and 80s elsewhere.

Key message 2: A series of storm systems will bring several rounds of rain chances through next week. Confidence in timing and any severe potential remains low at this time.

A pattern change will continue into next week with a cooler and wetter pattern returning to the region. A northern stream closed upper low over Canada will continue to slowly lift towards Hudson Bay with a belt of southern stream westerlies draped from the Desert Southwest into the Southern Appalachians. Several shortwave troughs will be embedded within the southern stream flow with the lead trough lifting across the Mississippi Valley on Monday. An associated band of convection will make a run at western portions of the area overnight into early Tuesday morning. How far any activity progresses into the area remains uncertain as the best height falls and forcing will be displaced farther north into the Ohio Valley. At the same time, a second wave will be ejecting out of the Four Corners and into the Southern Plains and Deep South on Tuesday with associated convection propagating east into the Southern Appalachians during the Tuesday night to Wednesday timeframe. The upstream environments both days, especially Tuesday across the Deep South, are supportive of severe weather. While some degree of severe potential cannot be ruled out into the western Carolinas and northeast Georgia, it will be dependent on how upstream convection evolves and to what degree the environment remains favorable farther east. Thereafter, guidance is in generally good agreement that a frontal boundary will clear the area on Thursday and bring at least a brief period of dry weather. A fast moving closed upper low is progged to eject into the Southern Plains on Friday and could bring another round of precipitation to the region late week.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

At KCLT and elsewhere: VFR conditions to start with brief restrictions possible overnight. A few showers are moving over the mountains and will continue to pop-up eastward through tonight. For the mountain terminals, -RA and SHRA should suffice. There is a chance for -RA and -TSRA elsewhere, so will keep the -TSRA in a TEMPO for the afternoon period. VCSH and -SHRA should continue into the overnight hours and low cigs could bring in MVFR restrictions. for KCLT/KGSP, SCT005 is also possible for a few hours before sunrise. Winds out of the SW with low-end gusts at KGSP/KCLT ahead of the weak cold front and turn N/NE tomorrow. Winds should remain light for Sunday.

Outlook: VFR conditions return Sunday and Monday. Another cold front on Tuesday could bring rain chances and possible flight restrictions.

GSP WATCHES/WARNINGS/ADVISORIES

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