COASTAL areas including Perth could have between 20mm to 55mm of rain on Sunday, with another 10mm to 35mm on Monday.
Strong winds ahead of the system on Saturday may cause dust storms through drier parts of the agricultural areas.
Swells of 5m to 6m are possible along the west coast from Exmouth to Israelite Bay on Monday and Tuesday.
The Bureau of Meteorology said the cloud band and cold front would pass over western parts of WA during the early hours of Sunday morning.
Moderate to heavy rainfall is forecast on Sunday for areas southwest of a line from Coral Bay to Cunderdin to Walpole with widespread falls of 20mm to 55mm possible, with isolated falls of up to 80mm.
For areas southwest of a line from Exmouth to Kalgoorlie to Albany, widespread rainfall totals of 10mm to 25mm are forecast, with isolated falls of up to 50mm possible. Communities along the south coast between Albany and Esperance that received heavy falls earlier in the week will only see light falls from this system.
On Monday, moderate to heavy rainfall will continue through areas southwest of a line from Geraldton to Cunderdin to Walpole, with 10-35mm of rain possible, and isolated falls of up to 65mm.
Parts of the eastern Pilbara, eastern Gascoyne, Goldfields, Interior and Eucla could have 5mm to 15mm on Monday too.
Dust storms are possible in the strong winds ahead of the rain on Saturday and Sunday with strong and gusty north to northeasterly winds likely to develop over the southern Gascoyne, western Goldfields and through the South West Land Division.
A cold, fresh and gusty southwesterly flow will then affect southwestern WA during Monday and Tuesday.
Coastal activities, such as swimming, surfing and rock fishing may be hazardous on Monday and Tuesday as swells of over 5m hit the west coast between Exmouth and Israelite Bay.
Dangerous surf conditions with significant beach erosion are likely.
People in western parts of the state are urged to keep an eye on BOM’s website and twitter feed for the latest updates.