Snow? ... There's a chance of falls in Canberra this weekend, but they are unlikely.
For those who got excited by momentary snow forecasts for Canberra on their iPhone or smartphone weather app over the coming weekend, the advice from the weather bureau is not to get your hopes up.
The Bureau of Meteorology’s Sean Carson said the chance of snow in Canberra was very, very slim, but said there was a chance the fluffy white stuff could fall anywhere on the Great Dividing Range sometime between Saturday night and Monday morning.
Mr Carson said the smartphone weather apps were responding to current weather conditions, as the south east of Australia continued to sit under a very cold air flow from the south.
“Your iPhone app is basically computer-generated data that’s not quality-controlled by meteorologists, and hence that’s why you don’t see that [snow] in our forecast at the moment,” he said.
“It’s cold enough to snow through many parts of the tableland at certain times of day at the moment, but there’s no moisture there to actually cause any precipitation.”
But the constant stream of cold air was expected to mix with warmer ocean air over the weekend, which would probably cause a low pressure system to form somewhere off the coast.
Mr Carson said depending on when, where and how strong that low pressure system was, there was a chance that moisture from the coast could meet the cold air somewhere along the mountains – but more likely somewhere like Armidale or Orange than in Canberra.
“If you can combine that moisture coming from the east with the atmosphere that’s cold enough to snow in the west, if you can bring them together for a short period of time, at the right time of the day which is generally in the morning hours after a very cold night, it could be cool enough to snow pretty much anywhere along the Great Dividing Range at some stage over this weekend,” he said.
“But it’s only a small window to get all those ingredients to line up, so it’s a chance, but it’s certainly not something that’s highly probable.”
But as the low pressure system hasn’t yet formed, and because it is an unusual weather pattern moving north-south rather than west-east, Mr Carson said conditions over the next few days would be “chaotic” for forecasting.
“Every time we’ve had an east coast low, you look back through history, it’s nearly always initiated snowfalls somewhere along the Great Dividing Range, either on the eastern side or the western side,” he said.
Despite the cold, Canberra’s geographic location made it an unlikely host for big dumps of snow. Significant precipitation was usually reserved for areas on the side of a significant mountain range facing an oncoming weather system.
But Canberra was wedged between two ranges, which meant most snow fell on or to the west of the Brindabellas, or, if the weather was coming from the east, precipitation fell more on the mountains to the east.
Mr Carson said the forecast for Canberra over the next few days was sketchy and depended on the formation of the low. Showers forecast for Sunday were a 50-50 call, and forecasts would likely change as the weather system took shape.
The forecast minus 5 degree-start to Friday has also been revised, with a slightly warmer minus 2 now forecast, while Saturday is still expected to drop to minus 4 degrees.
The weather pattern also meant it would be difficult to forecast snow over the weekend, with snow, rain, and even clear skies all a genuine possibility.
No comments:
Post a Comment