Australia Weather News

The storm is packing strong to gale force winds. (ABC News: James Carmody)

Residents of Western Australia's South West, including Perth, are being told to brace for severe weather and potential flooding as an intense storm system off the Indian Ocean tumbles toward the south west capes.

A severe weather warning has been issued for an area extending from Lancelin to Walpole, including Perth, Mandurah, Busselton, Bunbury, Margaret River and Manjimup.

The low pressure system, currently over waters to the west of the state, is expected to pass close to, but not over, the South-West capes late today and early tomorrow.

The storm is packing strong-to-gale force winds, with the Bureau of Meteorology (BOM) forecasting damaging winds with gusts up to 100 kilometres an hour for areas south of Mandurah.

Damaging wind gusts up to 90 kilometres an hour are possible between Mandurah and Lancelin overnight Wednesday and into Thursday morning.

BOM senior forecaster Matt Boterhoven said significant beach erosion was also likely, as well as possible flooding in Busselton, as the northerly winds pump the high tide mark up half a metre above normal.

"On its current track it is going to cause severe weather to the south west of the state and abnormally high tides, especially in the Bunbury-Geographe area," he said.

"There's still a bit of uncertainty of the low pressure system, and how that impacts the severity, but people should start preparing for damaging winds and be cautious around coastal areas during Thursday."

Mr Boterhoven said the winds would start to pick up from 3:00pm onwards today.

A sheep graziers' warning has also been issued for the South West, Great Southern, Central Wheatbelt and parts of the Central West, Lower West and South Coastal, with the BOM warning there may be losses of lambs and sheep exposed to the conditions windy, cold conditions.

Widespread rain forecast

The storm is also set to produce widespread rainfall to WA, with falls extending from western parts of the Pilbara through to Esperance.

Mr Boterhoven said rainfall in the range of 10–25 millimetres was expected for areas on the west coast, and between 5 and 15mm elsewhere in south-west land division.

"So that's fairly good rainfall and will just compliment what we had already in May," he said.

Areas of the West Pilbara and northern parts of the Gascoyne could get even heavier rain, with a forecast of 30 to 50mm of rain in Exmouth today and more tomorrow.

Mr Boterhoven said that may produce localised flash flooding.

Perth is expected to receive between 16 and 30mm of rain over the course of today and tomorrow.