GFS has -30 C at 500hPa over NE NSW/SE QLD this Sunday evening - temps that low that far north are exceptional.
Need to add this morning's BoM notes for the upcoming event:
"A high in the Tasman Sea will combine with a trough, presently over the Bight region, to generate a band of showers and storms in the west that will drift towards the ranges later tonight. The cloud will then drift out into the Tasman Sea during Friday. The trough will find it difficult to penetrate eastwards because of the strength of the high; it will still be west of Tasmania on Friday by which time it will be reinforced by the next system presently developing south of WA. The second system has all the makings of being an exceptional one. The cold air, already evident on the satellite photo, promises to be unseasonably cold, moving into the west of the state overnight Friday and reaching eastern parts by Sunday morning. There is a strong chance that the coldest air will move over the central and northern parts resulting in some snow about parts of the ranges."