Flood warning issued for northeast SA

A flood warning has been issued for South Australia's northeast pastoral region as a tropical low pressure system moves south from the Northern Territory.

Heavy rain will develop near the SA border late on Wednesday before extending further south on Thursday and Friday, the Bureau of Meteorology says.

Residents have been warned to expect road closures and to prepare to move to a safe location if flooding occurs.

Flooding has forced the closure of a 300km stretch of the NT's Stuart Highway and caused a woman aged in her 50s to drown.

NT authorities also hold grave fears for a man missing in floodwaters.