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Snowstack Mid-July Edition - While small meager top-ups have continued this week in the Aus alpine we take a look around the corner at the highly anticipated 'next big thing'.
*In this edition we get down into the weeds to breakdown the current broadscale pattern and give reason to the long range outlook. Keen to hear where and when it’ll snow? Just scroll on through to ‘Long Range Outlook‘.
Like a lump in the throat, you can’t see the apprehension, but you can feel it. The long-range has been teasing us for weeks now, and while it's kept us guessing, we’re starting to see with some clarity.
The old adage goes that good things come to those who wait, and though it's about a week behind schedule, we're now seeing a promising cluster of cold fronts materialise on the extended charts.
It’s uncommon to get much snow in the south-east, from a polar front peaking over southwest WA, but mid-winter dynamics are offering it transcontinental legs next week. Supportive temps and a trailing upper pattern suggest this energy may deliver by mid-next week, not once, but possibly back-to-back. Just as expected, albeit a little later than anticipated.
What’s behind this shift? A large, transient pulse of tropical convection has stirred the pot. The culprit: a meandering Madden-Julian Oscillation (MJO) threading its way through the Maritime Continent, nudging the polar storm track into action.
But this isn’t the first time this season the MJO has stirred something from the Southern Ocean for south-eastern Australia.
The MJO cycles through eight tropical phases, each linked to different regions of the tropics and capable of influencing weather patterns across the globe. In the absence of dominant seasonal drivers like El Niño, La Niña, a positive IOD, or a strongly phased SAM, the MJO stands out as the clear sub-seasonal force shaping our outlook.
Here’s why:
Under near-average climate conditions, the Madden-Julian Oscillation (MJO) has become a key player. This tropical pulse of convection typically begins over the Maritime Continent (phases 4 and 5), just north of Australia. As the MJO progresses eastward through phases 6 to 8, it enhances tropical storm activity and releases latent heat into the upper atmosphere.
This injection of energy disrupts the polar jet stream and perturbs the storm track encircling Antarctica. In winter, once the MJO reaches the Pacific (phases 7 and 8), it can trigger a chain reaction: amplifying the longwave pattern over the Tasman Sea (circa 150th meridian east), often resulting in a sequence of cold fronts sweeping across southeast Australia and the New Zealand Alps.
These longwave troughs are often the architects of mid-winter snow systems, and when timed right, can offer some of the most productive snow events of the season.
So, with the backstory out of the way, here’s how the MJO is tracked and forecasted: using a phase-space diagram that maps its progression through eight tropical phases. Numbered dots represent calendar days, and their position shows both the phase and strength of the signal. When the path moves outside the central circle, it indicates an active convective phase; inside the circle suggests weak or inactive conditions, typically too faint to influence large-scale weather patterns.
The recent delay in snow-bearing systems has been largely driven by the meandering and inconsistent behaviour of the MJO signal. As shown above, the BOM ACCESS-S2 forecast illustrates a coherent and strengthening signal progressing cleanly into phases 6–8, where we typically see enhanced potential for east coast troughing and polar front activity. Notably, the ensemble spread remains tight, reflecting strong model agreement.
In contrast, the ECMWF ensemble reveals a more scattered outlook, with the MJO lingering weakly over the Maritime Continent and struggling to exit into the Western Pacific. This divergence—particularly around July 20—has contributed to uncertainty in long-range forecasts. BOM's tighter clustering lends greater confidence in its projection, suggesting a more organised convective signal is finally taking shape.
Long Range Outlook
Skunked by a meandering MJO, the southeast is set for a pause in major frontal action this week. Instead, the outlook features clipper fronts and cool, mixed conditions across the alpine—offering a silver lining of decent resort riding and short touring windows.
A marginal system is expected to arrive late on 22 July, as a Bight-peaking front sweeps across the Australian Alps from the W/NW. Rain will likely begin in the alpine before a colder airmass moves in on the 23rd, dropping snow levels to around 1700 m. The high alpine may see 10–15 cm, though model divergence remains, and temperature forecasts are open to swings as the system approaches. It’s unfortunately not looking pretty for resort areas below 1700m with 20-30mm possible mid-next week.
The above system paves the way for a colder and stronger system due on Friday (25th), with a subsequent systems closing out July. These are the back-to-back systems we’ve been expecting. Whilst considerable divergence remains, there are indications of a cut off low in this last week of July possibly leading to prolonged period of snow in the SE (26-30th).
The 5-day ensembles anomaly via ECMWF supports the notion of strong polar systems due in the 27th July - 1st August window:
A mixed (and divergent) outlook is expected to return in early August for the Australian Alps, driven by renewed tropical activity in the Indian Ocean—that’s the IOD talking. However, early signs suggest the MJO may continue its transient path into the second and possibly third week of August.
NZ, We Need to Talk
In recent weeks, New Zealand has been basking in a considerable stretch of fine weather thanks to recent ridging, bookended by occasional snow in the main Otago and Canterbury resorts - while some of the club fields are still yet to open for the season.
The question remains, will August mark a change in this pattern? The above long range outlook suggests NZ may kick off August with a quick couple of large systems (possibly tied in with a negative SAM phase) however the seasonal models indicate a tricky time for NZ as it sits on the end of the peaking storm track, possibly leading to warm-advected systems, later in the month (seasonal model outlook below).
Copernicus (EC Seasonals) August Outlook
