Western Australia is set to be drenched from Sunday as a powerful cold front combines with a cloud band to produce thunderstorms and heavy falls which could lead to flash flooding.
The system is set to deliver rain to a large part of the state extending from the south coast to the Pilbara region.
Perth, which is tracking well below its winter rainfall average, could receive up to 35 millimetres on Sunday and up to 30 millimetres on Monday.
"It's not a typical cold front because of the interaction with the cloud band," Bureau of Meteorology (BOM) duty forecaster Jessica Lingard said.
"It's something that we would expect over spring time."
Heavy rain from Sunday afternoon
The rain-bearing cloud band will arrive early on Sunday, ahead of the cold front moving across the west coast on Sunday afternoon.
"For an area south-west of a line from Coral Bay to Cunderdin to Walpole, we're expecting falls of up to 20 to 55 millimetres (on Sunday) and even some isolated falls of up to 80 millimetres are possible," Ms Lingard said.
"For other areas extending south-west of a line from Exmouth to Kalgoorlie to Albany, we could see widespread falls of between 10 and 25 millimetres, with a chance of seeing higher falls of up to 50 millimetres."
Moderate to heavy falls will continue near the west coast on Monday.
Pockets of the state that are predominantly dry at this time of year could pick up a month's worth of rainfall.
"The triangle between Geraldton, Meekatharra and Carnarvon, their August rainfall averages are between 10 and 20 millimetres, so they could be looking at getting a month's worth of rainfall over four days," Ms Lingard said.
But the south coast between Albany and Esperance — an area that received heavy rain earlier this week — will only see light falls from this system.
Dust storms and dangerous coastal conditions
BOM is warning that winds will pick up ahead of the cold front approaching, potentially whipping up dust storms through the drier agricultural areas on Saturday and Sunday.
In the wake of the front on Sunday, a fresh and gusty south-westerly flow will create dangerous conditions along the west and south coasts.
"We are looking at a five- to six-metre swell affecting the coast between Exmouth and Israelite Bay (east of Esperance) on Monday and Tuesday, so surf conditions will be very dangerous and we could see significant beach erosion," Ms Lingard said.ABC