textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Tonight's threats for localized flooding and severe weather have largely passed.

Aviation discussion has been updated.

KEY MESSAGES

1. Cold air damming conditions and shower chances continue tonight, but The threat of heavy rainfall and flooding, as well as severe weather is waning. 2. Unsettled weather continues through most of next week as the large-scale pattern ushers Gulf moisture into the Carolinas and northeast Georgia.

DISCUSSION

Key message 1: Cold air damming conditions and shower chances continue tonight, but The threat of heavy rainfall and flooding, as well as severe weather is waning.

Cold air damming conditions remain fully ensconced across the area this evening, with low clouds and cool conditions lingering. Showers and isolated thunderstorms are largely contained to the unstable air in the vicinity of, and especially south of the CAD boundary. Even this activity has been steadily diminishing in terms of coverage and intensity over the past hour or so, and this trend will continue as the air mass steadily stabilizes in the warm sector.

Spotty showers will remain possible in light of the very moist air mass, weak isentropic lift, and weak upslope flow in place. However, the threats for localized flooding and especially severe weather appear to have passed. As the CAD gradually weakens/becomes increasingly shallow, dense fog may become a concern early Sunday, but this is far from certain at this juncture.

Key message 2: Unsettled weather continues through most of next week as the large-scale pattern ushers Gulf moisture into the Carolinas and northeast Georgia.

Synoptic guidance continues to indicate that broad troughing will remain in place across the central CONUS while upper ridging will stay centered over the western Atlantic from Sunday through much of next week. This configuration is favorable for steady moisture flux off the Gulf, meaning mainly diurnal periods of generally widespread convection should continue. Ensembles still struggle to consistently place the remnant frontal boundary, but by pattern recognition alone, periods of in-situ cold air damming would appear possible.

Confidence in specifics remains low as guidance continues to vary on which periods have the best precip chances and highest QPF, but there does appear to be some convergence on Monday having higher precip and heavy rain chances. One thing that's more certain is this: the dreary weather isn't going anywhere anytime soon.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

At KCLT and elsewhere: Lingering cold air damming (CAD) will result in continued low cigs through at least Sunday morning, with LIFR cigs expected to settle in at all TAF sites by around midnight. Reduced visby in BR is also expected to become more of a concern as NE winds steadily weaken, with 1-2SM expected at most sites during the overnight. Can't rule out lower visby, especially at KAVL. Shower coverage has diminished considerably across the Terminal Forecast Area this evening, and organized areas of precip are unlikely to impact the TAF sites until at least Sunday afternoon. Having said that, conditions will remain quite moist, so can't rule out a shower at any time & location tonight/tomorrow morning. This is handled with VCSH and/or Prob30s for -SHRA at all sites.

Confidence is modest at best regarding cig/visby trends beyond Sunday morning, but with conditions steadily becoming less favorable for CAD maintenance, it seems prudent to reflect steadily improving conditions to at least MVFR during the afternoon. The potential for diurnally-driven showers and thunderstorms will also increase during the afternoon, warranting Prob30s for -TSRA at most sites at some point during the afternoon/evening. ENE winds become light overnight, then light/variable or calm during the morning, likely becoming light southerly Sunday afternoon.

Outlook: The pattern will remain active for the foreseeable future, with above-normal coverage of diurnal convection and overnight fog/low clouds possible through the new work week. Periods of convection may also occur outside of the typical diurnal convective window.

GSP WATCHES/WARNINGS/ADVISORIES

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