Subtropical Storm Alberto is expected to remain well west of the Triangle as it moves north from the Gulf of Mexico, but the storm is helping to steer heavy, potentially flooding rains our way.
The National Weather Service has issued a flash flood watch for the Triangle, including Wake, Durham, Orange and Johnston counties and points south through 8 a.m. Tuesday. Rain moving north off the Atlantic Ocean was expected to arrive in the Triangle about 11 a.m. on Memorial Day and continue on and off through the evening and overnight hours.
Some of the rain will by heavy. Up to 2 inches of rain could fall in the Triangle by Tuesday morning, according to the weather service, with Johnston County and places south and east getting up to 3 inches.
The moisture pouring northward coincides with Subtropical Storm Alberto, which approached the Florida Panhandle from the Gulf on Monday morning with sustained winds of up to 65 mph. Tropical storm warnings were up for parts of the Panhandle and the Alabama coast.
Alberto is expected to drop 4 to 6 inches of rain along the Gulf Coast, with some places getting as much as a foot. The storm will weaken as it moves north through Tennessee and Kentucky into the Ohio Valley but will continue to produce large amounts of rain.
The counterclockwise spin of Alberto and the clockwise rotation of a high-pressure system in the Atlantic are combining to bring moisture northward into the Triangle, said Kathleen Carroll, a meteorologist at the weather service office in Raleigh.
“While the rain we’re getting appears to be influenced by Alberto, it is not necessarily a part of Alberto,” Carroll said.
The flow of moisture out of the South is expected to continue, bringing a chance of daytime showers and thunderstorms to the Triangle through the week and into the weekend, Carroll said. It's not clear what will become of the remnants of Alberto late in the week.
"Things are a little bit uncertain depending on the path Alberto takes," Carroll said. "How it becomes absorbed into the large-scale flow will determine whether we get any lingering effects from it."