Low pressure system has Qld on flood watch

Queenslanders have been warned to brace for potential flooding as a low pressure system threatens to dump huge amounts of rain on parts of the state.

The Bureau of Meteorology predicts rainfall could exceed 400mm from Thursday to early Saturday.

Queensland regional director Rob Webb says moist easterly winds combined with a strong upper air system are expected to bring heavy rain to coastal areas south of Gladstone, extending as far west as Roma.

"The Fraser Coast, Sunshine Coast, Brisbane and Gold Coast are all expected to feel the effects of the low from Wednesday night, with heavy rain, strengthening winds and large swells expected," Mr Webb said.

The weather bureau issued an initial flood watch on Wednesday afternoon, warning rainfall totals of between 200mm and 400mm were expected over coastal catchments but bigger falls were possible.

The rain event may also lead to localised flash flooding.