Synoptic Charts Weather Tutorial

Will it Snow?

Surely this is one of the most asked questions by skiers and boarders during the Australian winter. You can't help but find yourself suddenly glued to the TV during what was once a rather boring section of the news that came after the sport and before the good programs, the weather! But what does it all mean? Unfortunately not too many weather reporters around Australia are skiers, and hence, don't understand this daily fascination with the approaching low pressure system.

There are lots of pet theories out there, like when it is less than 14oC in Adelaide and raining it will snow in the Alps the next day, or if the ABC reports a "Sheep Graziers Alert for the Southern Highlands" it means business. Unfortunately like most fanciful concepts these are all too often wrong.

So what weather patterns are we looking for? At least then when the reporter is dribbling on about the conditions in Melbourne or Sydney we can work out the important stuff - WILL IT SNOW??

Basically there are two weather patterns that will produce snow, and these are often termed a "cold outbreak" and a "cut off".

Cold Outbreak

Usually responsible for dumping a lot of snow over a short period cold outbreaks are relatively common and can even occur during summer. Cold outbreaks are short lived fast moving fronts that will dump snow for one or two days. They are often accompanied with high winds (the isobars are close together) and followed by about 5 or 6 clear sunny days.

Cold outbreaks are common early and late in the season. They will often drop lots of snow in Tassie, and southern Victoria and may not even reach the more northern resorts.

Cutoff System

The key for a good season is a few good cut off low pressure systems. During summer the centre of the high pressure systems pass over Tasmania or Victoria resulting in easterly and north westerly winds. During winter the centre of the high pressure systems move north resulting in a stream of west or south westerly winds.

In certain conditions a low pressure system will feed cold air into the system and can result in snow falling for a week or more at a time. In this case the more northern resorts will often get a lot of snow while the more southern resorts can miss out!

Interpreting Satellite Photos

So there is a front approaching and a dirty great band of cloud associated with it, "yipee" you say, here it comes. Not necessarily! Check where the cloud band sits, if it is a dense arc shape preceding the front it is associated with the NW winds ahead of the front and is more likely to drop rain than snow.

The key is what is immediately behind the front, in the SW wind stream. If it is clear then we are unlikely to get much, if any snow. What you are looking for is a "speckled" effect in clouds following a front, it indicates cold moist air and is much more likely to drop snow.

What about El Nino and Global Warming

OK the planets warming up and the snow will melt and we will all have to take up grass skiing by 2010. We've all heard the stories.

The facts are a lot more obscure. Weather patterns are very complex and not yet fully understood. The general consensus is that there will be a steady decline in snowfalls in Australia over the next 70 years due to global warming. There are, however, models that actually predict increased snowfall for Australia. The trends seem to be to a slow decrease in snow depth but the cause is not fully understood and the studies continue.

Weather Discussion

Everyone has their pet theory, so if you think can predict when where and how much snow there will be from the weather patterns or the behaviour of your neighbours dog... join in on the Weather Discussion