Puerto Rico and the Virgin Islands braced for Tuesday's expected arrival of Tropical Storm Karen and its accompanying torrential rains and dangerous flooding, officials said.

The National Weather Service, in an advisory posted late Monday morning, said the region will experience "major rainfall" with flooding that "may prompt many evacuations and rescues" starting Tuesday morning.

Rain totaling 2 to 4 inches with "isolated 8 inches" will fall on the region, according to a National Hurricane Center advisory on Monday afternoon. Sustained winds of up to 40 mph are expected in eastern Puerto Rico and the U.S. and British Virgin Islands, forecasters said.

Potential Impacts expected with the passage of Tropical Storm Karen across Puerto Rico & the U.S. Virgin Islands. | Posibles impactos con el paso de la Tormenta Tropical Karen a través de Puerto Rico & las Islas Vírgenes Americanas. #prwx #usviwx pic.twitter.com/NfH4pWOrW7 — NWS San Juan (@NWSSanJuan) September 23, 2019

"Rivers and tributaries may rapidly overflow their banks in multiple places. Small streams, creeks, canals, arroyos, and ditches may become dangerous rivers," according to National Hurricane Center. "Floodwaters can enter many structures within multiple communities, some structures becoming uninhabitable or washed away."

The agency warned residents Monday to seek higher ground.

"Many places where floodwaters may cover escape routes. Streets and parking lots become rivers of moving water with underpasses submerged," the weather service said. "Driving conditions become dangerous. Many road and bridge closures with some weakened or washed out."

Puerto Rico Gov. Wanda Vázquez on Monday activated the National Guard and cancelled school.

As Karen moves north, it's not expected to make any radical western turns and could spare Florida.