textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Rain totals have slightly decreased through Friday for the NC Piedmont.

Shower and thunderstorm chances have trended drier for the start of next week.

KEY MESSAGES

1. Heavy rainfall and potential flash flooding through at least Friday. A Flood Watch is in effect through Thursday for much of western NC. 2. A return to typical summer weather beginning next week, with hot temperatures and daily thunderstorm chances.

DISCUSSION

Key message 1: Heavy rainfall and potential flash flooding through at least Friday. A Flood Watch is in effect through Thursday for much of western NC.

A complicated system continues to emerge as a boundary slowly pushes southward into the CWA. Ahead of it, elevated PWATs of 2"+ are setting the area up for a potential heavy rain event. Guidance has the Bermuda high to the east and TS Bertha to the southwest in LA allowing for a moisture fetch into the region. However, TS Bertha is much further west than model guidance, reducing the amount of moisture streaming into the area. Overall, this appears to be a slow moving system that looks to remain in play through at least Friday. SW winds appear to kick in a bit of a low level jet overnight, which may aid in further rain development, especially along the escarpment and into the foothills of SC/NC. At this time, guidance continues to highlight a swath of 1-2" of rain in western NC and into the NC Piedmont, with an increased concentration Thursday. Given any instability driven by daytime heating, convective rainfall rates could tick these totals up in isolated locations, increasing the risk for flash flooding. These locally higher amounts could range from 2-4". It's possible that as the boundary continues to sag south, rainfall totals could increase in Upstate SC. A Flood Watch is already in effect through 8 PM tonight for western NC. At this time, will keep the Upstate out of a Flood Watch as confidence is still not high enough to justify one, yet. How much rain does depend on where the axis of moisture transport sets up, which is highly dependent on where the boundary is. If the boundary slows and doesn't push as far south, the moisture piling could occur further west. Upper air support is also not a great factor as the area of better forcing is further east, outside of the CWA. However, if the boundary does advance further south, it could narrow the corridor of heavy rainfall to the western NC zones and into the Upstate through Friday, increasing the risk of flash flooding. So, all of this to say that rainfall is expected, but there still exists uncertainty of where the higher rainfall amounts could setup now through Friday.

Key message 2: A return to typical summer weather beginning next week, with hot temperatures and daily thunderstorm chances.

A strong ridge continues to build and remain over the western half of the CONUS. By Sunday, the southeast looks to remain in a more typical July pattern with increased temperatures and diurnally driven showers and thunderstorms. Daily PoP chances return to 10-30% without anything big driving the potential afternoon convection. Temperatures once again jump back into the 90s and hot heat index values return.

AVIATION /06Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: Showers creating restrictions as KHKY with MVFR cigs at KAVL. Expect IFR cigs to eventually develop at both locations with MVFR vsby in SHRA. Elsewhere, restrictions and showers will be slower to develop with MVFR by daybreak for all but KAND. IFR develops at the NC sites through the morning with IFR later in the afternoon over SC. Shower chances increase through the day with PROB30s for TSRA. Showers and TSRA chance continues into the evening with IFR for most locations. Low end gusty SW winds turn N then NE through the day as a boundary sinks south across the area. Wind remains N at KAVL through the day.

Outlook: Restrictions continue through Saturday as showers and thunderstorms remain. Much lower chances of convection and associated restrictions Sunday and Monday. Low stratus and/or fog are possible each morning in the mountain valleys and locations which receive heavy rainfall.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Flood Watch through this evening for NCZ033-035>037-048>053- 056>059-062>065-068>072-501>510. SC...None.