A slow-moving storm system, rich in moisture, has deposited up to half a foot of rain from South Carolina to Tennessee, leading to significant flooding issues.

Through midday Monday, Weather.com reported, the rains had “already forced water rescues, knocked out power to thousands and triggered significant flooding of multiple streets.”

Due to the deluge, the National Weather Service issued flood warnings and advisories in the Carolinas, northeastern Tennessee and western Virginia.

Several inches of additional rain could fall near the eastern border of North Carolina and South Carolina before the storm pulls off to the northeast Tuesday.

The storm system was made up of two areas of low pressure — one over South Carolina, and a second off the coast. The two were merging Monday, while directing a conveyor belt of Atlantic moisture from the Carolinas northwestward.

Because the storm system was largely cut off from the main atmospheric flow, it was moving at a snail’s pace, allowing rainfall amounts to pile up.

The heaviest rainfall was focused over northeast South Carolina and southeast North Carolina, where the Weather Service declared a moderate risk of excessive rainfall. “[We] would anticipate some isolated six to ten inches totals in this vicinity,” the Weather Service said.

A concern was that heavy storm cells could develop and track over the same areas repeatedly, a phenomenon known as “training.”

At 11 a.m. Eastern time, the Weather Service reported the following top rainfall amounts in Southeastern states:

  • Ringgold, Ga.: 3.72 inches
  • Winston-Salem, N.C.: 6.55 inches
  • St. Matthews, S.C.: 5.17 inches
  • Harriman, Tenn.: 5.71 inches
  • Meadows of Dan, Va.: 4.26 inches

Some of the hardest-hit areas in southeast North Carolina also endured significant flooding from Hurricane Matthew in the fall.

From Central Virginia and to the north through Maryland, the rainfall was gentler — with totals generally 0.1 to 0.5 inches. In these areas, the rain could linger into early Wednesday, but total amounts are forecast to reach only 0.5 to 2.0 inches as the core of the storm shifts offshore.

Setting the flooding aside, the rainfall was beneficial in many parts of the Southeast and Mid-Atlantic that were experiencing drought conditions.

Later this week, the drought could be declared over in certain areas when the U.S. Drought Monitor issues its next report.