Flash flood watches issued as Tropical Storm Bertha rain threatens a full Lake Wylie.
Newly named Tropical Storm Bertha could bring heavy rain to areas of the Catawba River, which are already all but flooding.
Bertha got her name early Wednesday morning after strengthening off the South Carolina coast. AccuWeather reports sustained winds of 35-44 mph with gusts at 40-50 mph. Tropical storm-level winds aren’t expected to last as the storm moves inland, but significant rain from Bertha could cover its in land path.
“Interaction with land and fast movement will be a great limiting factor with major strengthening of this feature,” said AccuWeather chief on-air meteorologist Bernie Rayno. “But the main impact will be a continuation of heavy rain moving forward during the middle of the week over the Carolinas then to some extent farther north over the central Appalachians from later Wednesday night to Thursday.”
On Wednesday morning the National Weather service issued a flash flood watch for Lancaster County through 10 p.m. Wednesday, including the Indian Land and Lancaster areas. It predicts 1 to 3 inches of rain.
“Tropical Storm Bertha will track northward across the central Carolinas today bringing moderate to heavy rain to parts of the Midlands,” according to the weather service. “The ground is already saturated from recent rainfall and stream levels are elevated, so any additional rainfall will quickly become runoff and cause rapid rises on area streams and creeks which could lead to flash flooding.”
Lancaster County also had a flood warning extended on the Wateree River, and a hazardous weather outlook noting strong thunderstorms and perhaps even tornado conditions on Wednesday.
York and Chester counties also have hazardous weather outlooks, with heavy rainfall and isolated flooding possible.
York, Lancaster and Chester counties just came off heavy rain that has area waters at or above spilling points. Of the 11 reservoirs on the Catawba River chain, three were above their full pond flood level at 9 a.m. Wednesday. Five more, including Lake Wylie, were within inches of their full pond levels.
Lake Wylie rose to its full pond on May 22-23. The lake rose about three feet in two days prior, as Duke Energy moved water out of the basin ahead of heavy rain forecasts then. Lakes throughout the basin dropped below target levels to make room for rain, then rose rapidly with storms.
As Bertha approaches, lakes already are high.
“The Duke Energy meteorological weather forecasts for Tropical Storm Bertha shows the storm having the potential to impact the Catawba-Wateree River Basin,” reads a Duke Energy public notice for Lake Wylie. “Lake Wylie’s lake level is above the normal target elevation and additional rainfall can cause higher lake levels. Duke Energy will continue to monitor the storm until the storm has passed. Hydro Operations is moving water through the river system to prepare for potential heavy rainfall. Individuals who live along lakes and rivers and in flood-prone areas should pay close attention to local media and changing weather conditions via the National Weather Service and take any necessary precautions.”
Potential lake flooding — along with creeks, streams and tributaries feeding them — isn’t just about the rain that falls on that lake. Heavy rain anywhere in the Catawba basin impacts other areas, as Duke runs or holds water with its reservoirs in effort to prevent heavy flooding anywhere.
The projected path of Bertha runs pretty close to the Catawba basin footprint.
The 225-mile basin with 5,000 miles of waterway runs from the Blue Ridge Mountains in North Carolina to central South Carolina. The basin covers all or part of 24 counties in two states.
The National Weather Service shows a flood warning, flash flood watch or hazardous weather outlook for all of them.
At 2 p.m. Wednesday, Duke sent out a new public notification. It notes widespread spilling could occur.
“Recent changes in meteorological forecasts for Tropical Storm Bertha indicate the storm has the potential to impact the Catawba-Wateree and Yadkin-Pee Dee river basins, which are above target levels due to recent rainfall,” it reads. “Additional rainfall could result in higher lake levels and widespread spilling on basin reservoirs.”
A little before noon Wednesday a flash flood watch was issued for several counties including York, through late Wednesday. It notes the Rock Hill area in particular. Nearly saturated ground and stream levels, it notes, mixed with expected rainfall will cause rapid stream rises.
Check back for more.
This story was originally published May 27, 2020 at 10:48 AM.
