Polar outbreak hitting eastern Australia to bring most snowfall in two years across NSW over next 24 hours

The most widespread snowfall in at least two years is currently developing across NSW, with dozens of towns along the Great Dividing Range likely to see flakes during the next 24 hours.

The snowfalls are part of broader polar outbreak currently hammering eastern Australia – an event which has already delivered the coldest day in years to parts of NSW on Monday and promises to bring even icier weather on Tuesday.

For the higher alps, half a metre of snow could accumulate during the next 48 hours, bringing relief to ski resorts after an exceptionally poor start to the season.

Snow ahead for dozens of towns

After an unprecedented year without snow in 2023, elevated parts of NSW are finally turning white.

The first dusting arrived on Sunday across the alps and higher Central Tablelands, before starting a descent to lower elevations on Monday, including an early morning dusting at Crookwell posted to the ABC's Weather Obsessed Facebook page.

Snow then increased on Monday afternoon as a sub-Antarctic air mass was intersected by a tongue of moisture from the Tasman Sea, courtesy of a deep low-pressure system just offshore.

Snowfalls should become even more widespread tonight, spreading to more highly populated stretches of the ranges.

So which towns can expect to wake to snow on Tuesday morning? 

The freezing level, the minimum altitude where the air temperature is below zero, should hover around the 1,000-metre mark overnight.

Snow typically falls 100 or 200 metres below the freezing level, since falling flakes won't melt instantaneously, which should lead to a snow level of around 800 to 900 metres.

The heaviest snow on Monday evening will initially fall over the southern ranges and alps, including possibly around Jindabyne, Cooma and Nimmitabel.

It will also come very close to snowing in Canberra by around midnight, before the heaviest non-alpine falls shift to the central ranges on Tuesday morning, including around Crookwell, Taralga, Oberon, Orange, Lithgow and possibly the Blue Mountains.

By Tuesday night, the heaviest snow should shift to the upper Hunter and Northern Tablelands which could see flakes falling over Armidale, Guyra and Glen Innes.

Warmer air wrapping around the offshore Tasman low will then contract the snow level back to the alps on Wednesday.

Polar air brings lowest temperatures in years

Snow events are significant for low maximum temperatures, as opposed to frost events which bring low minimum temperatures.

Daytime highs on Monday were as much as six below normal in NSW, including a high of only 4.2 degrees Celsius in Orange — the city's coldest day in two years.

NSW will again shiver through well below average maximums on Tuesday, including highs of only around 4C to 7C on the Northern Tablelands, also potentially the region's chilliest day in three years.

While slightly warmer weather will arrive by Wednesday, in most parts of the state temperatures will remain below average until at least Sunday.

Alps rejoice in heaviest snowfall of season

For ski resorts the snowfalls are almost at the season-saving level after the worst start to a winter in 23 years, based off natural snow depth at Deep Creek.

Snow commenced on Sunday afternoon across resorts and intensified Monday as the Tasman Low approached eastern Bass Strait.

By Monday afternoon, at least 10cm had accumulated across the resorts and the heaviest snow is still ahead overnight with blizzards potentially dropping close to 50cm in just 24 hours.

Lighter snow will fall on Wednesday before another burst of snow arrives on Saturday, setting up a platform for a solid base if further heavy snow arrives during the back half of winter.