textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Slight increase in rain chances Wednesday and Thursday.

KEY MESSAGES

1. Another round of strong to severe thunderstorms are possible ahead of a cold front this afternoon into early evening. The primary concerns from any stronger storms are damaging wind gusts and excessive rainfall. 2. Much cooler temperatures filter into the region Wednesday and fall below normal into Thursday. A few pockets of rainfall possible before drier conditions develop by Friday.

DISCUSSION

Key message 1: Another round of strong to severe thunderstorms are possible ahead of a cold front this afternoon into early evening. The primary concerns from any stronger storms are damaging wind gusts and excessive rainfall.

With the first day of Fall upon us, mother nature on queue shifts a frontal boundary toward the area. Ahead of the cold front, another round of showers and thunderstorms this afternoon and into the evening hours. The broad open warm sector provides some moisture and daytime heating, instability as fuel for these storms. As the front advances, this should provide enough of a trigger to pop off storms throughout the entire area. A few of these storms could become severe with the main hazard being damaging winds and locally heavy rainfall. For this, the Storm Prediction Center has continued with a Marginal (risk 1 of 5) for the entire CWA. Guidance shows timing starting over the mountains as early as 1 PM and quickly moving eastward through the 10 PM to midnight timeframe. If the front advances quicker, it cuts off the fuel for storms, hence ending thunderstorm chances. Either way, one more day of pesky showers and thunderstorms before relief from months of daily storms and heat arrives.

Key message 2: Much cooler temperatures filter into the region Wednesday and fall below normal into Thursday. A few pockets of rainfall possible before drier conditions develop by Friday.

The area becomes stuck in between a relatively strong rex block, with a ridge to the west and upper trough to the north/northeast. This starts to breakdown by the weekend as an amplifying upper low parks over the northeast and reinforces cooler and drier air into the CWA through the end of Day 7. Wednesday and Thursday look to be the more somewhat wetter days, as cold air damming develops Tuesday night and remains in place through at least Saturday. Remaining moisture and northeast surface winds, help to reinforce cloud cover and pockets of rainfall in showers. With the CAD in place, confidence is higher that convection should not be an issue and any rainfall would just be from lingering moisture being forced upwards on the terrain. By Friday, the area of low pressure lifts further off the northeast coastline, filtering in even drier air with a backdoor cold front, snuffing out rain chances through the foreseeable future. Temps look to be well below normal for Wed/Thurs with highs in the 60s for the majority of the area, before ticking upward into the normal range for the remainder of the forecast.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

At KCLT and elsewhere: A few scattered -TSRA over KAVL should dissipate by 07z. FG likely at KHKY/KAVL 08z-13z. Otherwise, MVFR cigs with intermittent IFR through early morning at all sites. A cold front from the west brings another round of TSRA to all terminals between 19-20z and lasts through 00z-02z. There could be lingering SHRA after at most sites. Winds prevail NE, but light at all sites. IFR cigs prevail at KCLT through 12z Tuesday.

Outlook: Restrictions likely through Thursday, with breezy winds. Drier conditions return Friday into the weekend, though mountain/river valley fog/stratus could still develop near daybreak each day.

GSP WATCHES/WARNINGS/ADVISORIES

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