A thunderstorm that prompted the National Weather Service to issue Severe Thunderstorm Warnings for the Greenville area and parts of Spartanburg county on Friday morning is part of a larger weather system that is expected to bring additional strong thunderstorms to the state this afternoon and evening.
Unseasonably high humidity has surged northward from the Gulf of Mexico and is blanketing the state. The moisture content of the air and warm afternoon temperatures into the 80s will make the air unstable enough for thunderstorms as the cold front approaches from Georgia and Alabama. NOAA’s Storm Prediction Center has issued a “slight risk” (level 2 out of a possible 5) for severe thunderstorms for most of the Midlands and Upstate. It also issued a “marginal risk” (level 1) for areas as far south and east as I-95.
Storms are expected to gradually organize over parts of the Upstate between noon and 3 PM, then spread to to the Midlands early this evening, before moving off the coast shortly before midnight. Here is the best estimate of the arrival time for the storms:
Greenville/Spartanburg 2-4 PM ET
Rock Hill 4-6 PM ET
North Augusta 4-6 PM ET
Columbia 4-6 PM
Aiken 4-6 PM
Orangeburg 5-7 PM
Florence 6-8 PM
Myrtle Beach/Charleston 7-10 PM
Additional rain is also expected from the thunderstorms, but heavy rain on Thursday night in the Upstate prompted Flood Watches in the mountains, where more than 5 inches was reported about north of Travelers Rest in the Greenville county. The National Weather Service says an additional 1 to 2 inches are forecast, but locally higher amounts may occur along south-facing slopes. They added that streams and main stem rivers are rising from recent heavy rainfall, making flooding more likely with any more rain today. Heavy rain over the rest of the state will depend on exactly where the storms form, but is expected to be less than what falls over the Upstate.
Much cooler air will follow the front this weekend and the National Weather Service in Greenville says there may be patches of frost in the Upstate Saturday night into Sunday morning.