Friday: Light snow today. Snow/rain mainly overnight on weekend. Rain Monday then a big, snowy week.
A large high pressure system covers much of the country, but its centred to our north letting a cold front clip Victoria's coast later today. This produces foggy cloud and light snow, and its remaining cold enough for snow down to 1500 metres.
The centre of the high moves to our northeast for the weekend, letting it warm up somewhat. A cold front slides through early on Sunday, with precipitation overnight and through some of the morning, then it dries up quickly. We've warmed a bit by this stage, but it could still be a wet snow above 1700 metres. Much of the daylight hours of the weekend will be dry.
The next strong front approaches on Monday, and it warms up a little bit more in the strong northwesterly airflow. We'll see rain during the day with 20 to 40 mm (it doesn't have the same tropical moisture link as the last 100mm+ rain), but that could be as wet snow at times above 1900 metres, possibly 1800 metres.
The cold air arrives on Monday evening (from southwest to northeast: late afternoon/early evening at Mt Buller - late evening at Selwyn), and should produce 10 to 20 centimetres before easing in the morning.
Then it gets interesting. This pattern will jump around on the models, but it should end up with a high near New Zealand making a complex area of low pressure linger to our southeast. This will let moisture, instability and cold enough air all work together to let snow wrap around and spread across the alps. And, if the main low sits in the right spot, then it will produce a lot of snow, as it looks like this pattern will persist through the week and possibly across the weekend. Stay tuned...
It all comes down to a simple equation. To make it snow you must have: low pressure, moisture and cold enough temperatures.
We can guess the moisture part of the equation for the season ahead by looking far away from the alpine areas, and considering the balance of warm and cool water in both the Pacific and Indian Ocean.
Pacific Ocean: El Nino is over and we will have a Neutral or La Nina phase instead. Neutral would be a good source of moisture, and La Nina would be a great source. La Nina would also work to push it towards the alps.
Indian Ocean: a negative Indian Ocean Dipole (IOD) is the most likely situation for this winter. This means that the waters off Indonesia are warmer than the waters off Kenya, meaning more moisture for us to play with. And the atmosphere responds to this imbalance, by pushing it towards the alps.
So, that, combined with warm waters off much of the coastline of Australia, all works to ensure the moisture part of the equation is as good as it can ever be.
But, what about the low pressure and temperature parts?
These are the big questions for 2016. We don’t have any good guidance to show how many low pressure systems will move through, and whether they will take a helpful path. And, all this warm water around us means that our air temperatures may be warmer rather than cooler.
My feeling is that we will have several ridiculously huge dumps of snow (thanks to high moisture), producing some absolutely epic days this season. But what happens in between those only time will tell…