Jane Bunn - Snow Forecast

Thu 19:00pm 17 Sep

Updated: Thursday September 17th, 7pm

This will be my last forecast for the season, but I’m looking forward to a brilliant 2021. janesweather is launching soon, with better maps and snow alerts - the future looks bright. In the mean time, keep up to date with the drivers of our weather here.

Patchy, light rain continues on Friday. Cloudy but not adding up to much.

An inland low affects us on the weekend. Warm and sunny on Saturday, but… the alps have the risk of afternoon and evening thunderstorms. Precipitation increases to persistent rain after midnight, into Sunday morning, as the low approaches. It could be heavy. As the low passes later on Sunday, it breaks to showers and the risk of further storms. This weekend could bring 20 to 30 mm of rain, possibly more in storms. All too warm for snow, in fact its a taste of Queensland’s humidity.

There is a short break on Monday morning, then a band of rain passes through on Monday afternoon and evening. Again, there is no cold air, but 10 to 30 mm of rain.

After all that passes… snow finally returns. A cold front or two gets up high enough to bring snow showers, at higher alpine elevations, later Tuesday and on Wednesday, possibly lasting to Thursday. Higher slopes could see 10 to 20 cm of snow.

There may be another snow system late in the week - check the individual resort pages for guidance.

Day by day details:

FRIDAY: Generally cloudy with light rain at times.

SATURDAY: Warm, sunny and humid… before the risk of thunderstorms in the afternoon and evening. Widespread rain develops late at night, potentially heavy.

SUNDAY: Persistent rain in the morning, potentially heavy. Breaking to showers and thunderstorms in the afternoon and evening.

MONDAY: A dry break in the morning (and part of the afternoon in the east). Rain redeveloping in the afternoon and evening.

TUESDAY: Showers likely. Turning to snow showers up high later in the day/at night.

WEDNESDAY and THURSDAY: Snow showers likely.

(check individual resort pages for specific hour by hour guidance from the EC model)

HOUR BY HOUR DETAILS FOR YOUR RESORT:

Mt Buller | Hotham | Falls Creek | Mt Baw Baw 
Perisher | Thredbo | Charlotte Pass | Selwyn 
Lake Mountain | Mt Stirling | Ben Lomond | Mt Mawson 
Mt Dandenong | Mt Donna Buang | Mt Macedon 

Where is the snow?

During May and June we were in a long phase of weather known as a positive SAM (Southern Annular Mode). Over the alps in winter, it makes cold fronts weaker, puts high pressure in control, or brings cutoff/complex lows that can bring a lot of rain (as they generally don’t have a good cold pool that you get from a strong front).

This positive phase turned negative, late June into early July. That made cold fronts with snowy cold pools a bit more likely. (Not guaranteed with every negative phase, but strong fronts can rise up and hit the alps more easily. You still get periods of high pressure in between though…).

There was another negative surge mid July, turning neutral again a few days later ahead of another negative surge to finish the month.

We entered positive for the first week of August, then it tumbled, with a stretch of negative across the middle of August. This lead to the series of cold fronts around the weekend of the 22nd/23rd. The signal started to head back to neutral on the 18th, before another negative dip for the last week of the month, producing excellent snowfalls.

SAM spent the first week of September negative, then went into positive for mid-September. The positive signal encourages lows and troughs to form over eastern Australia, limiting how strong the cold fronts can be. Outlooks show a range of outcomes, between positive and negative for the rest of September - see the latest output here.

Key to terminology: Is it precipitation that lasts a long time, or starts and stops?

Showers - Precipitation that starts and stops. Bursts/cells of rain or snow that move through the area in a hit and miss fashion. ‘Widespread showers’ means they are more frequent, the dry breaks in between are shorter. ‘Isolated showers’ means there are long dry breaks, and the showers could even miss the slope (it may actually be quite sunny).

Persistent - Precipitation that is continuous for several hours. Most parts of the mountain are affected for a long time. Rain or snow, depending on the temperature.

 

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