Polar outbreak and snow ahead this week with Sydney and Melbourne on track for coldest start to winter in decades (2024)

Parts of south-east Australia have recorded their coldest start to winter in decades and another polar air mass will arrive during the coming week, promising to bring strong winds, showers, small hail and alpine snow.

In the meantime, a cold and showery weekend is already underway across southern Western Australia and the New South Wales coast, while frost has returned to the south-east inland after an icy week that brought subzero temperatures as far north as central Queensland.

Adding to the wintry systems, a major low-pressure system should soak WA from Wednesday onwards, continuing the recovery from a record drought in the state's west.

Polar outbreak and snow ahead this week with Sydney and Melbourne on track for coldest start to winter in decades (1)

Showers in Sydney and Perth, frosty nights for Canberra, Melbourne

Yet another cold and showery weekend is developing along the NSW coast as cold southerly winds drive in showers off the Tasman Sea.

For Sydney, the soaking makes six wet weekends out of the past eight, and the city now only needs another 44 millimetres to surpass its annual average rainfall for an entire year.

By 9am Friday, Observatory Hill had received 1,178mm in 2024 (see below graph), about 1,000mm above most other capitals, apart from Darwin and Brisbane.

The heaviest rain this weekend is likely from the Illawarra to the Mid North Coast, where up to 50mm could accumulate, although it's possible the most intense showers will remain just offshore.

Winds blowing nearly parallel to the coastline will prevent heavy showers from penetrating far inland, leading to totals of only 1 to 10mm across Western Sydney and other areas adjacent to the coast.

Showers will also impact Perth and much of western WA on Saturday, as a cold front arrives from the Southern Ocean, bringing further relief after an exceptionally dry start to 2024.

Most regions from about Perth to Albany can expect about 10mm, before showers contract to the south coast of WA on Sunday.

For the remainder of southern Australia, clear skies and light winds will provide the optimal conditions for cold overnight temperatures this weekend.

Polar outbreak and snow ahead this week with Sydney and Melbourne on track for coldest start to winter in decades (2)

Minimums will not be as extreme as the past few days, however, frost on Sunday morning will extend from Tasmania, through the south-east into southern Queensland and the southern Northern Territory.

Frost could even return to Melbourne on Saturday night with a forecast minimum of 3 degrees Celsius for the CBD and 0C in the outer suburbs.

Snow dump possible this week for the Alps

The freezing weather during the past fortnight has not translated to heavy snow across the Alps due to a lack of precipitation.

But a welcome boost to the snow depth should arrive this week ahead of the school holidays.

Polar outbreak and snow ahead this week with Sydney and Melbourne on track for coldest start to winter in decades (3)

The cold front currently bringing rain to Perth will reach South Australia on Monday, then south-east states on Tuesday, bringing a burst of strong winds, showers, and cold temperatures.

The polar air associated with the system will also generate a few thunderstorms and pockets of small hail, while bringing a fresh dump of alpine snow.

Showers and alpine snowfalls should then linger on and south of the ranges through Wednesday.

Current modelling indicates the system could bring up to 50mm in areas exposed to a westerly, including Adelaide where 2024 has so far produced just 132mm of rain.

For the Alps, the system could produce about 20 to 30 centimetres of fresh snow, not particularly high by Australian alpine standards but beneficial considering ongoing cold temperatures will preserve the current cover.

Polar outbreak and snow ahead this week with Sydney and Melbourne on track for coldest start to winter in decades (4)

While the south-east remains under winter's grip, WA can expect a rare northward-drifting low-pressure system that will drop Perth's air pressure to abnormally depressed levels.

What's unusual about the system is winter lows normally remain well to the south, with only their associated front extending north to WA to deliver rain.

However, the centre of this week's low could drift as far north as Perth and its attached front may even penetrate into the tropics.

Perth's air pressure could approach its lowest value of the past 50 years of 990 hectopascal (hPa).

The result of the deep and large system will be strong winds and widespread rain across WA for about 72 hours, starting from about Wednesday, before shifting to south-east states towards next weekend.

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Was the BOM's warm winter prediction wrong?

Seasonal forecasts have consistently predicted this June and winter as a whole to be warmer than normal — so was the Bureau Of Meteorology's (BOM) modelling way off the mark?

The short answer is no, because for most of Australia, it hasn't been particularly cold. However, unfortunately for BOM, the one region where temperatures have been consistently cold just happens to include most of NSW and Victoria, our most highly populated states.

The perception of a cold start to winter is also perhaps the result of a handful of extremely cold days and nights during the past week, along with the recent trend of very warm winters.

Take Sydney, for example — the city's average maximum this month has been about half a degree warmer than the long-term average, threatening to become the coldest start to winter since 2007.

Melbourne's maximums of 14.1C this month are bang on the long-term average, but much colder than most Junes this century — currently the equal lowest since 1995, although for the first three weeks of June, the city's temperatures have been the coldest in 35 years.

Melbourne's overnight temperatures have also dipped well below recent years — average minimums of 6.8C this month have been the equal coldest since 2006.

And while June has been noticeably cool for south-east Australia, given the fickle nature of Australia's weather, that's no indication July and August will follow suit, thus a declaration the winter outlook was wrong is, for now, premature.

Posted, updated

Polar outbreak and snow ahead this week with Sydney and Melbourne on track for coldest start to winter in decades (2024)

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