Snow is coming along with a week of rain as a huge cold front sweeps across Australia. Courtesy Seven News

THIS thing is going to be massive. America had its Polar Vortex in 2013, when frigid air streamed down from the north pole causing major snowfalls and record cold temperatures.

Eastern Australia, it’s your turn now.

Prepare for the Antarctic Vortex. That’s not a technical term. It’s the nickname we’ve given this weather system, but we’re sticking with it. Others, meanwhile, have developed their own monikers.

#Snownami. Starts tomorrow. Runs at least 3 days. Probably longer. 50cm minimum. 100cm possible. Maybe more in some places. #BeThere. -CW — ski.com.au (@skicomau) July 9, 2015

It’s now only a day or so until the Vortex roars across eastern Australia, bringing freezing temperatures and the likelihood of prolonged snowfalls to low levels. In the mountains things have already kicked off this morning, as the 11am “beer-o-meter” pic demonstrates.

And here’s a Friday lunchtime picture from Black Sallees Mountain Bistro in Thredbo, which we’re sure serves generous portions of delicious everything.

As you no doubt know, it’s not unusual for the Australian Alps to experience heavy snowfalls at this time of year. It’s also common to see snow flurries on some of the higher towns and lesser mountain ranges in eastern Australia during brief cold outbreaks

But this storm is different. The Antarctic Vortex will be big and the Antarctic Vortex will be long-lasting. If forecasts hold true, the Antarctic Vortex looks set to deliver freezing temps and heavy snowfalls to a vast arc of eastern Australia from the hills outside Melbourne to the ranges west of Brisbane.

Here’s Sunday’s snow forecast:

And here’s Monday’s:

“It’s really a very big airmass change,” says Andrew Haig from the Bureau of Meteorology NSW regional office. “It is a very extensive area of cold air which has dragged up cold air from a long way south.

Meteorologists don’t always talk about surface temperatures like the rest of us. That’s because surface temperatures vary according to elevation, topography, the “urban heat island” effect in cities, plus a range of other factors.

Instead, they talk up about upper air temps, or “uppers” as they call them. These are a truer reflection of the actual temperature of an airmass. And the uppers on this incoming storm are mind-blowing.

“We’re looking at uppers not much above zero at three thousand feet,” Andrew Haig says.

Put simply, that means any town situated at 900 metres above sea level or thereabouts (or higher) can expect some serious snowfall. That includes places like Orange and Katoomba, west of Sydney and Armidale on the NSW Northern Tablelands.

“The upshot is these places could get 10 to 20 centimetres of snow if it all comes off,” Haig says.

As stated above, snowfalls have already started today in the Snowy Mountains of NSW and Victorian Alps, as you can see in the images above and below.

But the coldest blast is likely to strike Sunday into Monday, when the snow level is tipped to be as low as 600 metres, which is the level of most Canberra suburbs.

These weather systems usually fizzle out shortly after the coldest air arrives. Not this time. The Antarctic Vortex is different from other storms not just in its intensity but its likely duration.

This colossal conveyor belt of cold is set to linger for at least a week — and we’ll keep you updated with developing news, road closures and of course snow pics right here.