This morning's snow forecast has quickly changed from a sad looking chart, to something with a lot more zeal. Some alpine resorts have a forecast of 80cm of snow over the next ten days!
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Hold on... before you get too excited, let's look under the hood to see what is driving that forecast.
Those big numbers don't appear until later in the forecast period (days 6 to 10) and the rainfall range couldn't be any larger (one has a range of 0.4cm to 80 cm).
There are two problems there:
1) Forecasts become less accurate the further out you go (and days 6 to 10 are a long way from now)
2) While one model has 80cm, another is forecasting only 0.4cm
We always need to wait until the models form a consensus, ie they are all on the same page and forecasting a similar outlook, before we have any confidence in the outlook.
THE OUTLOOK - SHORT TERM
After a long period of hot and generally dry thanks to dominating high pressure, we are seeing the potential for a few snow systems.
In order to make it rain you need moisture and instability to work together. In order to make it snow, you need to add cold air into the mix.
The first potential snow system is this weekend. A stronger cold front is likely to burst through the dominant ridge of high pressure, bringing a shot of cold air. But the high pressure only weakens slightly, and we're missing a key ingredient here to get snow - instability. The pressure won't go low enough to get the decent amounts we need. It'll be plenty cold enough... snow should lower to 600 metres in Tasmania on Saturday (potentially 400m in the far south), 1200 metres in Victoria (mainly on Sunday), and 1500 metres in NSW (also on Sunday).
Here is the situation on Saturday night with the big shot of cold air coming up from the south:
Cold yes... dumping snow no... as the pressure is not even remotely low (it's up on about 1020hPa). On a side note, this cold air will then move over the Tasman Sea and deepen into proper low pressure, producing huge rainfalls for the NSW coast early next week. This area isn't stuck under the dominant high ridge.
THE OUTLOOK - LONGER TERM
The Euro model is the one that's getting excited about bigger snow falls later on in the outlook, with a system coming up around Thursday and another a full 10 days away - next Sunday.
I'd wait until the other models have at least a hint of this action too. At the moment they have a few centimetres of snow at best, and don't like the strong shots of cold air and dip into low pressure that the Euro model has currently.
You want all four models (shown in the pastel colours) on the same page - not just one showing you the good stuff - on Thursday into Friday:
And on Sunday - a full ten days away:
Don't miss the snow forecast summary to keep up to date with the latest, where you can check the hour by hour details for your favourite resort.
