This synchronised animation of hourly infrared satellite images, radar and lightning tracker shows the causes of today's widespread snow. See the article for explanation. The satellite images, although carrying on-the-hour timestamps, are actually created about 30 minutes before the hour. Radar images therefore are about 15 minutes behind the satellite image. Note that radar coverage of the area is not complete, with no coverage in NW NSW, scattered radar shadows in other areas, and some individual radar installations, notably the East Sale radar, periodically diverted to weather balloon tracking duties. This unusual presentation represents the combined resources of Weatherzone, Kattron, the BoM and GMS-5 backup with GOES-9 operated by the joint effort of JMA and US NOAA NESDIS over the Western Pacific.

Widespread deep snow in NSW, VIC, TAS

An intensely cold airmass swept across southeastern states today bringing widespread snow and traffic chaos before spawning a rapidly developing East Coast Low. The wave of cold air was transported northwards on Thursday and Friday from around 55°S by a sharp, full-depth atmosphere trough. This crossed the southeastern SA coast late yesterday morning with the cold air following overnight. A strong surface high of over 1040hPa established itself in the cold air to the west of Adelaide in the wake of the trough. It ridged southeast under TAS during today, cutting off the trough and forming an upper low over southern NSW. When this and the cold air arrived over the warmer-than-normal waters off the NSW South Coast this afternoon, a surface low formed and deepened rapidly, accompanied by widespread thunderstorms in the western Tasman. Gales and high seas followed (see report for Sunday).

Where, when and why the snow fell today is best explained by the synchronised animation of hourly satellite and radar/lightning tracker images at right.

3am to 9am: At 3am, a cold front extends from eastern Victoria through the southern NSW inland to NW NSW. A broad area of cloud has developed up the NSW South and Central Coasts in the uplift ahead of the front, while the lightning out in the Tasman shows the line of a prefrontal trough. In the first few frames, a kink develops along the frontal cloud line SW of the ACT as the upper trough begins to cut off, and in the frames from 6 to 9am the clouds west of Canberra begin to circulate as the upper low develops downwards toward the surface. The circulation and the cold air moving in aloft combine to produce precipitation around Cooma and Canberra. A clear, windless night had given the Southern Tablelands temperatures around dawn of -4 or -5° and these only rose to around zero before the cloud cover moved in. At 9am, Canberra Airport was -0.5 and Cooma town +1.0. The rain you can see developing on the radar therefore fell as snow from Canberra southwards.

9am to 3pm: The circulation, cold pool and precipitation move ENE, arriving in the Goulburn area late morning and giving the city several hours of snow. From about midday, a second cloudmass moves northwards through eastern VIC and into the Monaro area around Cooma, bringing heavy snow in the ranges around the NSW/VIC border which spills as far north as Cooma. Also from midday, thunderstorms develop explosively off the South Coast as air as cold as -15° at 700hPa (10,000 feet) and -32 at 500hPa creates massive instability.

3pm to 3am: By 3pm, rotation in the cloud places the developing off the southern Illawarra Coast. Several cloudmasses and their attendant rain echoes can be followed over the next 12 hours as they rotate underneath the low, then return northwards across the coast and over the NSW Southern Highlands and Central Tablelands. The cloudmass that gave snow to the Northern Tablelands late Saturday and early Sunday can be seen breaking away from the western edge of the main cloud area centred on the ACT mid morning. It then makes its separate way NE, gaining some intensity mid afternoon over the Central Western Slopes before arriving on the Northern Tablelands this evening. To the south, low (grey) cloud can be seen streaming northwards across the far eastern VIC coastline. Though only low level cloud, it gave abundant moisture and heavy snow in the ranges south of Bombala.

The snow event by district

Tasmania: Snow fell as low as 200m around Hobart, closing the Mt Wellington Summit Road at The Springs. Snow was reported at Palmers Lookout (190m asl) behind Port Arthur and at Maydena (280m asl) in the Derwent Valley while at sea level sleet was reported at Orford on the East Coast and ice pellets at Dover in the southeast. While snow was widespread over the island it was mostly light. The Mt Field ski area west of Hobart, however, gained 15cm of fresh snow overnight into Sunday.

Western VIC: Roads were closed and conditions treacherous around Mt Macedon where snow fell down to 600m and was around 10cm deep on the summit. Light snow fell in Kyneton (520m asl), Woodend (560m) and Macedon (500m) and settled at Trentham (680m). Sleet was reported this morning in the Otway ranges below 400m asl.

Northeastern VIC: 20cm of snow closed the Great Alpine Road from Harrietville to Mt Hotham until 7am Sunday, isolating the resort and stranding a number of motorists. Strong winds rendered snowploughs useless, with roads icing over soon after they were cleared. Chairlifts were closed by the strong winds.

NSW Monaro/VIC East Gippsland: The area around Bombala experienced its heaviest snow since 1987. This area to the east of the NSW/VIC Alps requires a cold, moist southerly airstream to deliver substantial snow. These are fairly rare. Thirty to 50cm of snow closed all main roads and isolated and blacked out several small settlements in VIC for 3 to 5 days. The satellite animation shows a steady southerly stream of moisture crossing the East Gippsland coast. As this was pushed over the ranges around the NSW/VIC border, the uplift produced steady light to moderate precipitation which fell as snow from late this morning until Sunday afternoon. This was heaviest on the south-facing slopes of the Great Divide as well as in the elevated region around Nimmitabel where 5cm had accumulated by 2pm and 15 to 20cm by 5pm today. By mid afternoon there were reports of about 2cm snow in Cooma and 10cm in Adaminaby. Maximum snow depths reported by the Bombala Times were Bonang 43cm, Bendoc 36, Delegate 20 and Bombala, Ando, Bibbenluke and Cathcart about 15, showing a gradual reduction north of the Divide. Snow depths on high, south-facing slopes are likely to have been half a metre to a metre, with drifts several times as high.

The snow brought transport in the area to a standstill for most of the weekend with all main roads impassable. Vehicles were abandonned or ran off roads as snow caught travellers unawares, and police rescued a number of people from stranded vehicles. The population of Bombala swelled considerably on Saturday night with marooned motorists. In NSW, the Snowy Mountains Highway was closed between Cooma and Bemboka, the Bonang Highway between Bombala and Delegate, and the Monaro Highway south to the VIC border. Later in the day, the Monaro Highway was reported closed between Queanbeyan and Cooma. These roads were opened during Sunday or early Monday, but even on Monday there was snow on the Monaro Highway between Nimmitabel and Bombala.

In VIC, the Cann Valley Highway (the VIC extension of the Monaro) was closed off at Cann River. Road graders were sent to the Bonang Highway between Orbost and Delegate enabling the road to be kept open, though icy, through Saturday. However, they lost the battle as heavy overnight snow into Sunday was accompanied by rising winds as the east coast low wound up adding fallen trees and branches to the ice and snow. All cross-border routes apart from the Princes Highway were impassable by Sunday morning. These included the Monaro/Cann Valley Highway, the Bonang Highway and Gelantipy Road north of Buchan. Graders and road clearing machines worked first to clear fallen trees then to deal with the snow, but it was Tuesday or Wednesday before main roads were open, and even longer for minor routes and property access roads.

The area worst affected by the snow and wind was around Bonang in VIC, halfway between Orbost and Bombala. Half a metre or more of snow closed roads and knocked out power in the area for between 3 and 5 days. In this area, southerly winds are funnelled up the narrowing Brodribb River valley into a labyrinth of ridges rising to 1300m around the Errinundra Plateau. Combienbar AWS, on the Plateau's southeastern side at 640m asl, recorded 50mm between 9am today and 3pm Sunday. The reported temperature during these 30 hours was mostly between 0 and 2° so the precipitation would have fallen as snow and an accumulation of 50cm is a reasonable assumption.

By Sunday morning, all roads around Bonang and the neighboring settlements of Bendoc to the NE and Tubbut to the NW were blocked by fallen trees and around half a metre of snow. Added to the inconvenience of isolation, however, was the hardship of blackouts that began on Sunday night and lasted until Wednesday or Thursday depriving properties of heating, cooking, lighting and water pumps. Power company Country Energy's Southeast Regional General Manager David Bellew told ABC Radio "The volume of snow and the high winds were unusual. The powerlines were physically broken by the ice and wind in four places, and 14 trees had fallen across our access tracks." Until the Bonang Highway was opened through to Delegate River on Tuesday or Wednesday, linesmen were forced to use snowmobiles to get to damaged powerlines and do patrols. "We've had a plane fly over (the powerlines). That unfortunately could not land at Delegate because the airfield is snowed in so it has had to go down the coast", Mr Bellew said.

With roads closed, people who could not trudge through the snow to stores in Bonang or Bendoc had to rely on stored food. Tubbut Primary School classes were cancelled for most of the week with their bus route blocked and their teacher isolated by snow. Secondary school students from Tubbut, Bonang and Delegate were also unable to get to school in Bombala. A revealing impression of the event was given by a farmer interviewed on ABC Radio: "On Monday I came back from Sydney, and I have a large herd to feed but I couldn't get to it because the road was closed. I got stuck in a snow drift. We have no mobile service so I had to walk about two miles back to Bonang in the dark, with snow up to my knees and in civilian clothes. And when I got back to the telephone booth at the general store, guess what? The phone was out. I've got one stud cow down, so I'm out about $2000, and I can't get to the rest of the herd."

NSW Snowy Mountains: Heavy snow in the Berridale and Jindabyne areas caused many accidents and cars running off roads, keeping police, SES and fire brigades busy. About 11am a truck crashed into a power pole on the outskirts of Jindabyne, blacking out half of the town for more than 2 hours. In Jindabyne, snow was deep enough to allow skiing and snowboarding down the streets. At one stage mid-morning, all roads into the town were cut for about 2 hours, with movement impossible even with chains or 4WD. Slush on the roads turned to ice as temperatures dropped, and with many weekend visitors eager to see the snow, traffic chaos ensued. At Perisher Valley, 20cm of snow fell in 24 hours, while reduced visibility and high winds closed many chairlifts. Roads were salted and sanded to improve traction, but remained icy.

Canberra/Goulburn: Snow flurries were reported in the higher parts of Canberra during the morning. Heavy snow was reported from Goulburn and from Gunning to the west and Collector to the southwest from late morning to early afternoon. Two centimetres was reported on the ground in Goulburn about 2pm and traffic snow advisories were issued for the Hume and Federal Highways. One traveller reported continuous snow on the ground from Lake George to Marulan.

This extraordinary scene for NSW was taken from Bass Point, Shellharbour, looking WSW toward the Barren Grounds, south of Robertson. The ridge on the skyline is about 600m asl, with the snowfield above the surf about 500m asl. Shoalhaven Weather

Southern Highlands NSW: Snow in the Moss Vale to Robertson area was the heaviest for 10 years according to the SES. The snow extended as far as Barrengarry Mountain, with Barrengarry farmer Trevor Parrish telling the Illawarra Mercury that the whole escarpment was covered with powdery white snow. Snow also fell briefly at Cambewarra Lookout Tearooms around 10.30pm. Falls as low as 600m covered Robertson, Mittagong, Moss Vale and Bowral with up to 7 or 8cm on the ground by late Saturday evening closing the Illawarra Highway and local roads west of Robertson, and causing icy conditions on the Hume Highway south of Mittagong.

The road up Mt Gibraltar at Mittagong soon after daybreak on Sunday morning. Up to 7cm snow cover was reported in the Bowral to Robertson area of the Southern Highlands, with deeper drifts from strong winds overnight. Mittagong Weather

Blue Mountains and Central West: Snow fell across the Blue Mountains and much of the Central Tablelands this evening and through into Sunday morning. Lighter falls were reported earlier in the day around and south of Oberon, settling in the Shooters Hill area from late morning. The heaviest falls overall were in this area with average depths of 10 to 15cm and drifts above 25cm, but snow fell as low as Woodstock (470m asl), 25km NE of Cowra, and was also reported from Mt McDonald, Mandurama, Blayney and Bathurst. There was a light dusting of snow around Orange, but snow coated the summit of nearby Mount Canobolas through Sunday and Monday. About 20 cars had to be helped by SES crews after they slid on icy roads around the mountain during the weekend.

In the Blue Mountains, snow fell lightly from around 6pm today, but a heavier fall late evening and early Sunday morning closed the Great Western Highway west of Katoomba to Lithgow and also Bells Line of Road, effectively blocking all roads west of Sydney for a period. Snow and ice around Mt Lambie closed the Great Western Highway there for a time on Sunday morning. Two to 3cm was reported on the ground from Wentworth Falls westward, with 5cm at Lithgow at 9am Sunday morning. Falling snow this evening was reported as low as 600m at Hazelbrook.

Snow 25 to 30cm deep was reported from the higher parts of the Barrington Tops where snow continued to fall for most of Sunday. Hunter Valley Weather

Sydney: Showers of hail were reported from many suburbs during the day. The temperature at Observatory Hill at 1.30am Sunday was 6.0 with wind at Fort Denison 51 gusting 72km/h. The lowest temperature recorded at Observatory hill since 1858 is 2.1, giving some indication of the unusual coldness of this airmass.

Northern Tablelands NSW: Heavy snow fell along the Northern Tablelands from the Nowendoc region SE of Tamworth north to Ben Lomond south of Glen Innes. Temperatures farther north were low enough for snow, but there was no precipitation. The New England Highway was closed for several hours early Sunday morning between Armidale and Guyra, and until late Sunday morning in the Guyra area. Guyra reported 7cm on the ground at 9am Sunday while locals at Niangala, 50km SE of Tamworth, reported 5cm on the ground on Sunday morning. It was Guyra's third snowfall of the year, following 4cm on 20 June and 3cm on 8 July. Light snow fell in Armidale producing a thin blanket of white that vanished with sunrise on Sunday.

The Barrington Tops, which rise to nearly 1600m about 100km NNW of Newcastle, are well exposed to southerly winds. Snow fell heavily overnight and through Sunday, with depths reported to be the greatest in 8 years. On the Moonan Flat side on Sunday, snow was reported on the ground as low as 600m, was 12cm deep at 900m and 25 to 30cm at Polblue camping area, at about 1500m. The Scone to Gloucester forest road across the Tops quickly became impassable, trapping 15 people who had to walk off the mountain before being taken to Moonan Flat for overnight shelter. The snow and ice on the mountain road gave police a chaotic situation on Sunday as sightseers flocked to the area. A four-car collision occurred when a Landrover lost traction while driving down the mountain, and slid sideways coming to a stop on the edge of a 400m drop. Three following cars also lost control and collided with one another. Police had to rescue the driver of the Landrover because of the precarious situation, then had to systematically remove about 200 vehicles stranded on the road. The road was closed for several days.

Mid North Coast: A curious report comes from The Tuncurry Great Lakes Advocate to complete the story of this exceptional weekend. Under the banner "IT SNOWED in Forster on Sunday afternoon!" is this report of snow on the coast 30km S of Taree, NSW. "And at least 20 people saw it - including ministers - according to chiropractor Keith Bastian. They were on a second floor, at the Level 2 restaurant in Wharf Street, for a meeting of the Christian City Church Great Lakes when they noticed snow flakes falling, about 3.40. 'There were people there from places such as England and Hobart and Orange-Bathurst and they know snow,' Keith said. 'They were good-sized flakes, about thumbnail size and we saw them hitting the windows. They were quite visible. They didn't settle for long, of course, because it had been raining. We watched them for about 20 minutes before they eased off'."

The unusual meteorological situation for Sunday is described more fully here. Temperatures at 3pm Sunday at Forster Beach, Taree Airport, Port Macquarie Airport and Nelson Head were all between 10.1 and 10.8°. A narrow band of heavy rainfall had given Forster Beach 40mm between 9am and 3pm, and the observer there reported intermittent moderate rain and a relative humidity of 100% at 3pm. The upper air situation was complex, with a band of warmer, moist air wrapping around the low well to the east of Forster, but a mass of very cold air still lying along the NSW ranges, and still producing snow on the Barrington Tops about 60km to the west of Forster. The coast near Forster was therefore very close to a sharp upper air temperature differential, and the observations of the Christian City Church members may therefore be as accurate as they are impeccable.