A deep low-pressure system is moving close to WA, with heavy rainfall, damaging winds and big surf on the cards today and tomorrow.

The strongest winds are predicted in the southwest of WA, while the heavy rainfall and large surf are forecast to reach as far north as the Pilbara region.

-- WINDS --

As the low nears southwestern WA tonight and tomorrow morning, damaging wind gusts of 90-100 km/h are possible in the area southwest of Mandurah.

While gales are not out of the ordinary during winter for these parts, northerly winds of this strength are. Usually, low pressure systems or fronts bring gale force southerlies to the area during winter, rather than northerlies.

The unusual wind direction in combination with the gale strength, has the potential to damage houses and infrastructure. Winds are expected to ease from tomorrow afternoon as the low slips to the south of WA.

The strongest winds in Perth are likely to occur this afternoon and overnight, with damaging gusts possible, particularly near the coast.

Image: Forecast accumulated rain during from Wednesday to Fruday (left) and forecast wind speed and direction on Wednesday morning (right) showing the low pressure system over the Indian Ocean.

-- HEAVY RAINFALL --

The low is also expected to bring heavy rain to parts of southwestern WA. During the next 72- hours, rainfall totals of 30-40mm are forecast for parts of the western Gascoyne, far southwestern Pilbara and right down the southern coastline to the southwest district. There is potential for pockets of 50-60mm to fall along the coastal fringe of these areas, with much of this rainfall falling later tonight into tomorrow.

-- DAMAGING SURF --

The low-pressure system is also expected to whip up some large waves from today until Friday morning. The combination of higher-than-normal tides and damaging surf may bring the risk of flooding to low lying coastal areas along the coastline. Beach erosion is also a risk for parts of the west coast.

Check the latest severe weather warnings in WA for up-to-date information on this system.