Queensland communities ravaged by Cyclone Debbie are bracing to be hit by even worse floods, with more than a month's worth of rain set to fall along the eastern seaboard by the weekend.
Battered Airlie Beach and Proserpine could be dealt a devastating blow, with the soil still wet from the rain, winds and storms that lashed the region.
"The rainfall could be comparable," Sky News Weather meteorologist Tristan Meyer told news.com.au.
"Flash flooding and river flooding are the main threats, and that's going to be at the forefront of people's minds."
Fitzroy River and the Rockhampton region, which suffered major flooding during Debbie, is not set to be hammered as hard this week, but "further north, it's more up in the air".
Meyer warned that "the rain is probably going to be in the order of what we saw", and while it won't be accompanied by the gale-force winds and tidal surge that made Debbie so destructive, the flooding could come faster.
Flash flooding, which is more common in urban areas, tends to arrive and retreat quickly, while river flooding is slower and takes longer to clear.
"There's a danger of both," said Meyer. "The river flooding could last until Monday.
"The catchment is prone to flooding again and will probably react quicker because of the moisture in the soil."
The Isaac River catchment is one of several likely to flood, in what could be nightmare for towns still rebuilding after severe cyclone damage.
Brisbane is set to be the worst affected of the capital cities as a low pressure system creeps up on the entire eastern seaboard.
The heavy rain is forecast to begin late tonight, with a low and trough in the south triggering patchy rain, showers and thunderstorms across South Australia and western Victoria, according to WeatherZone.
Heavy showers and storms will build across eastern parts of SA, Victoria, much of western NSW and western Queensland tomorrow, with winds bringing showers to the NSW coast.
By Friday, the rain and storms will become widespread and heavier for Queensland (particularly the coast), NSW and parts of Victoria.
The rain band will move from west to east across Australia's eastern states and build until Saturday, which will be the wettest, with a deluge expected over a wide area.
As much as 100-250mm of rain is due to fall between Tully and Mackay, and inland to just east of Mirimbah can expect "rain and even some storms within it", according to Meyer. "The Murray Darling Basin is still set to see a month's worth of rain in a weekend," he added.
It could see up to five times the average rainfall for May falling in just three days.
And while the worst will be over, there'll be little respite from the soggy feet next week, with intermittent showers expected to continue.
Bureau of Meteorology National Operations Centre Senior Meteorologist Scott Williams told news.com.au that the average rainfall would be 100-200mm, reaching up to 400mm in some parts of Queensland.
Lismore CBD is flooded after the Wilson River breached its banks early today. Photo/Dave Hunt/AAP
During Cyclone Debbie, the average was between 300-800mm.
"Some of these areas, because there's been so much showery weather since [Cyclone Debbie], the ground is still wet, so it might not take much to get back to flood levels," he said.
"It's pretty significant for this time of year outside the cyclone season."
The BOM issued a Flood Watch was yesterday for coastal catchments from Cairns to Gladstone, including Townsville, Mackay and Rockhampton, extending inland to include parts of the Burdekin and Fitzroy catchments.
Flooded roads in Mudgeeraba after cyclone Debbie ripped through northern Queensland. Photo/AAP
"We're looking at Thursday being very active for rainfall on the Queensland coast, especially the area from about Innisfail to Gladstone, with totals broadly 100 to 200mm in that area," Williams said.
"[On Friday,] we'll see a lot of thunderstorm activity develop through western Queensland and extend down into western New South Wales. While the totals won't be as large as in Queensland, isolated locations in western NSW could receive up to 100mm depending on thunderstorm activity."
The Bureau expects to issue a Flood Watch for all northern Tasmanian river basins from Thursday.
Rainfall is also expected in Western Australia, as a series of cold fronts will bring a much-needed downpour of up to 50mm into the south west of the state from Thursday.
