Big weather system rolling through, but it may only be cold enough for higher elevations

A huge weather system is rolling across NSW this week, as a cold outbreak crosses Tasmania - but we are missing a key ingredient over the mainland alps: cold air.

Tasmania's cold outbreak is from later Monday into Tuesday, with low level snow in the south. None of this reaches the mainland alps.

The big low rolling across NSW is driven by a nice pool of cold air - but most of that cold air is trapped back to our west. It'll provide plenty of energy to the weather system but will struggle to make it cold enough for most alpine elevations.

The low passes through on Wednesday into Thursday, and the heaviest precipitation falls on Wednesday. Incredibly high peaks could do incredibly well with all of this as snow. 1700-1800 metres will be borderline - possibly lots of snow, but likely to be quite wet snow. Below 1600 metres should be mostly rain until the precipitation rates decline and the cold air comes in.

This is a classic example where some of the 'rules' don't always work. There is a rule of thumb that if it is 15C or lower in Melbourne then it's cold enough for snow in the alps. Wednesday in Melbourne will struggle to rise above 12C. But it's the cloud and cool air that is creating that chill, rather than a proper feed of cold air.

The wind direction also shines some light on why this may not be cold enough: it's an East to Southeasterly (because the low is crossing NSW).

We could be incredibly lucky here and have pockets of cold enough air meet up with the heavier precipitation, and those above 1600 metres have a fantastic Wednesday, but do be aware that may not be the case. Later Wednesday or early Thursday looks better for cold air, but the precip tapers off.