* Around 4 mln T of wheat could face losses, quality downgrades
* Crop yet to be harvested in key growing areas of east coast
* Troubled wheat growing season, first drought, now excess rains (Adds details, quotes, graphics)
SYDNEY, Dec 1 (Reuters) - Heavy rains in eastern Australia forecast to intensify over the weekend are threatening to wipe out or damage up to 4 million tonnes of wheat due to be harvested shortly, forecasters said on Friday.
Most of the state of Victoria and parts of the states of South Australia and New South Wales were facing a "major weather event" in the coming days from torrential rains, according to Australia's Bureau of Meteorology.
Australian farmers have had a rough wheat growing season this year. A severe drought earlier in the year reduced yields, with the world's fourth-largest wheat exporter set to harvest its smallest crop in a decade.
Australia's winter this year, which runs from June to September in the Southern Hemisphere, was the warmest since records began more than a century ago, and also among the top 10 driest seasons ever.
Globally, there is no shortage of wheat. The U.S. Department of Agriculture is estimating world inventories at a record 267.53 million tonnes at the end of the crop year in June 2018. The Chicago Board of Trade December wheat futures hit a contract low on Tuesday and were trading at $4.09-1/4 per bushel on Friday.
Around 50 percent of the crop has been harvested in South Australia but in Victoria and southern parts of New South Wales only about 30 percent of the crop has been gathered, according to analysts.
"The main concern is that these are the areas where crops are still being harvested," said James Maxwell of Australian Crop Forecasters, which expects to downgrade its national wheat forecast of 21.7 million tonnes once the damage is assessed.
"At the moment, we estimate that around 4 million tonnes will be affected," Maxwell said.
It was not yet possible to determine how much of the crop would be wiped out and how much is downgraded due to the onset of re-sprouting, or premature germination, resulting in lower yields.
Victoria could see the loss or damage of up to 1.7 million tonnes, according to Maxwell.
In New South Wales and South Australia combined the figure for losses could reach as high as 1.9 million tonnes, Maxwell said.
Bureau of Meteorology forecaster Scott Williams said the rain would fall heavy and fast, with the potential of more than 50 millimetres (1.97 inches) in just an hour.
Rainfall in excess of 250mm is forecast by the Bureau of Meteorology for parts of eastern Victoria, with the overall state expected to see more than 60mm.
Victoria's state premier, Daniel Andrews urged people to brace for a "very challenging period" over the next few days.
"This is a very serious matter, and one that will pose a real challenge to communities right across the state and will be a direct challenge to public safety," he told reporters.
Prices for wheat from Australia's East Coast have risen by about A$10 a tonne to around A$280 ($212) a tonne this week, reflecting a premium for the risk of crop losses, said analysts.
"We fear more of a quality downgrade rather yield losses," said Brett Cooper, Asia head of agricultural commodities at brokerage INTL FCStone in Sydney.
"There could be more feed quality wheat and that will support global high-protein wheat prices." ($1 = 1.3228 Australian dollars)
(Reporting by James Regan in SYDNEY and Naveen Thukral in SINGAPORE; Editing by Christian Schmollinger)