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The next major weather system arrives in alpine areas on Monday to Wednesday or Thursday.
It will not begin well for the alps.
The atmosphere warms too much in the days prior, so the beginning of this is most definitely rain. And the colder air may not arrive until we've had a lot of that rain.
On Monday, gusty northwesterly winds bring above freezing conditions, as rain slowly develops. That rain increases during the afternoon and evening, coming in from the northwest. It may turn quite heavy in the early hours of Tuesday.
On Tuesday it continues raining.. as colder air approaches from the west. The timing of this colder air will be the big question with this weather system. If it speeds up then we get more snow while the falls are heavy. If it comes in slowly we only see the change over to snow at the end of this first period of precipitation.
That's just the first bit, and things look much better when we get to the second and (potentially) third waves of precipitation.
The snow should increase later on Tuesday in this second wave, continuing into Wednesday.
Some models then also have a third wave on Wednesday, with a big burst of snow lingering into Thursday.
-> So there is snow on the way, but we have a lot of rain to get through first. The changeover looks to be on Tuesday afternoon or evening.
A common practice is to look at the daily weather charts, that show how much precipitation is likely over a 24 hour period from 10pm to 10pm - ie the chart for Tuesday is the 24 hours up until 10pm on Tuesday. (Why 10pm? 10pm AEST is midday in UTC time, a key model timestep, and that's what the global models all work from for consistency)
On this map, we layer over the thickness line, the infamous '540 line', to see how cold the air is.
Cold air + precipitation = snow!
Remember that the thickness pattern is not for the duration of the rainfall - but rather it is for a static period in time at the end of the forecast period, in. this case 10pm on Tuesday.
That's why this first map looks fantastic (as it stands at 5pm on Thursday 19th June) ...
... but in reality it may not be. The cold air doesn't arrive until later on Tuesday, which may not be while most of the precipitation is falling.
