Here are some ideas about how to have fun and be safe on spring snow! Understand ‘melt-freeze cycles’ and have fun with spring snow!
When cold dry snow melts in the sun/heat during the day and then freezes at night that is a melt-freeze cycle. Once that occurs several times in succession, the top snow layer begins to form a crust that gets deeper and stronger after each melt allows free water to drip down and re-freeze during the night. Any given ‘melt-freeze’ layer becomes stronger with each cycle of melting and freezing due to the deeper penetration of each melt during the day, which then adds more depth to the potential frozen layer at night.
If untouched, the top of this frozen layer is smooth and solid first thing in the morning, then it becomes progressively softer as the warm sun and increased temperatures melt it as the day goes by. This process starts on east faces because they get the sun first thing in the morning, then south, then west (north faces at/above 2500 in the metres in the Alps don’t normally get a melt freeze layer on them until late April due to lack of heating from the sun. But once they do, you can ski well into the afternoon after a good freeze at night).
For good spring skiing!
The trick is, after a couple of good melt-freeze cycles have created a solid layer on a slope, you need to get on that slope when the snow surface is smooth and solid with only 2 or 3 cm’s of soft melted snow on top (these are generally slopes that have been in the direct sunlight only for an hour or two e.g. an East facing slope at 9 or 10 am).
Then you need to get off those slopes when the snow surface begins to get too soft and mushy or you’ll start breaking through, which is dangerous for your knees. AND the slope may be unstable due to all the melting – then avalanches can be a problem on these sunny slopes from the lack of stability due to melting of the bonds between snow crystals and snow layers.
After a solid melt-freeze layer has formed and there has been a good melt during the day, it needs to freeze well the next night in order for it to be right for the next day – the ideal is a cool clear night; for example: minimums of –2 degrees (or lower) at 2000 m if your going to be skiing at 2000m and above. This will allow the melted parts of the layer to freeze solid again from that altitude up and that will pretty much guarantee that it will support your weight the next day.
Then, in the morning, you look to get on the east facing slopes first thing, 9 AM, because the sun rises in the east and therefore those slopes get the sun first. Then you move to south facing slopes, then west. Do this right and get some of the best skiing of the season.
Aside from a night that is not cool enough, the only thing that gets in the way of great spring skiing is the nasty ruts in the snow that people leave behind because they either ski spring snow slopes (slopes that get lots of sun in spring: E,S and W) before the melt-freeze layer has formed (too soon after a snowfall) or they ski the slopes too late when they are too soft and mushy.