textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated PoP, temp, visibility trends overnight. Revised key message 1 and aviation discussions accordingly.

KEY MESSAGES

1. Showers taper off 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: Showers taper off tonight before drier air returns for Sunday.

A weak cold front appears to have settled through most of the area. Remaining rainfall is not expected to be sufficient to cause any hydrologic issues, with rain having been beneficial today. Aside from a couple of isolated stripes of 1" to 1.5" totals from the embedded convection, most areas have seen a few hundredths to three tenths of an inch. Light showers remain across much of the area but those should generally taper off from west to east through midnight or so. The southward progress of the front is expected to slow overnight, remaining near our southeastern CWA border. Shortwave trough now over eastern KY/TN will shift overhead and could allow redevelopment of showers over the southern Upstate and the southeastern fringe of the Charlotte metro. A stray thunderstorm can't be entirely ruled out, though we only managed a handful across our whole area during peak heating this afternoon, and profiles don't look to become any more favorable overnight, so thunder looks quite unlikely tonight. Cloud cover will be slow to erode overnight, but also tending to occur west to east. Areas of fog may develop with the boundary layer being nearly saturated, particularly in the mountain valleys and upper reaches of the Catawba/Broad valleys, those areas all potentially clearing sooner. Very light northerly winds are expected to keep fog potential relatively low, so if/where winds remain calm overnight and decent rainfall fell in the afternoon/evening, locally dense fog could become possible.

Dry air returns for Sunday with rapid clearing expected during the morning. 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 /00Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: Shift to northerly winds has occurred at all the TAF terminals, with cold front having settled south of the area. -SHRA should taper off from west to east through 04z or so, though new development of SHRA may occur later in the night near KCLT, KGSP, KGMU as front slows and shortwave trough moves overhead. Remaining chance of TS is small enough not to mention at any site, so only -SHRA. A brief period of IFR is possible as rain ends this evening, particularly at KAND. Otherwise, expecting development of MVFR to IFR cigs to occur by 03-04z with nocturnal cooling, and with low-level drying not looking to occur until a secondary front comes in from the north Sunday morning. Some areas of MVFR to IFR vsby will develop overnight though light winds should promote enough mixing to make cigs the main driver of restrictions. Improvement in cigs should occur 12-14z with a few MVFR to low VFR cumulus possibly developing, though that is unlikely to produce cigs. Winds will veer to NE by Sunday morning except at KAVL which should remain NW.

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

GSP WATCHES/WARNINGS/ADVISORIES

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