Flash Flood Risk Increasing over South Carolina from Sally Later This Week
The threat of flash flooding is likely to increase over parts of the Palmetto State late Wednesday and Thursday as slow-moving Hurricane Sally makes a move toward the state.
The storm was already drenching the Florida Panhandle and the Alabama Gulf Coast Tuesday morning. Forecasters at the National Hurricane Center said historic flooding was possible there on Wednesday as Sally heads toward landfall between the Mississippi coast and the Florida Panhandle. The winds associated with Sally will weaken as it moves across Alabama and Georgia Thursday and Friday, but torrential rain and flash flooding is likely to reach South Carolina as copious moisture streams in ahead of the center of the storm.
Model simulations suggest the first of the rain bands may arrive over the state on Wednesday afternoon; however, a stationary front in the area is also supplying the focus for the initial rain. More widespread rain is likely on Thursday as the center of Sally gets closer to the state. Scattered downpours may continue into Friday and the remnant of Sally is likely to depart into the Atlantic waters over the upcoming weekend.
Confidence is increasing for a significant flash flood event, particularly in the #Upstate of #SouthCarolina from #Sally. Some rain arrives later Wednesday, but main event looks to be Thursday. Rainfall amounts of 5-10" are currently forecast by @NWSWPC through the event. #scwx pic.twitter.com/Wnl5NkOxya— Ray Hawthorne (@ray_hawthorne) September 15, 2020
The greatest risk of flash flooding is over the Upstate region based on the latest forecasts from NOAA’s Weather Prediction Center. However, some risk of flash flooding is possible statewide. Rainfall amounts of 5 to 10 inches are possible over the Upstate, while 2 to 5 inches are possible over the rest of the state. The rainfall projections may change depending on the exact track of Sally over the next couple of days.
Forecasters said it was too soon to determine whether tornadoes would develop in advance of Sally over South Carolina.
Hurricane Paulette and Tropical Storm Teddy are expected to stay over the open Tropical Atlantic Ocean over the next week. Long-period swell and rip currents from those storms are expected to continue along the South Carolina coast, where a high risk of rip currents has been issued. Additionally, persistent onshore winds, the new moon phase, and the perigee are expected to cause coastal flooding near the times of high tide in the early morning and early evening hours. The latest forecast at Charleston indications moderate to major coastal flooding from these influences Tuesday and Wednesday evenings.
Major coastal flooding is forecast for tomorrow evening's high tide in Downtown Charleston. At 8.0 ft MLLW widespread flooding occurs in Downtown Charleston with numerous roads flooded and impassable and some impact to structures. Visit https://t.co/UfKqVAm7cZ for more info pic.twitter.com/x1Ejv6gv1p— NWS Charleston, SC (@NWSCharlestonSC) September 15, 2020