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Everybody likes to ski in the sunshine; it makes you feel good, and you can clearly see where you’re going. However, as the skiing season progresses the temperature gradually rises as spring approaches. But how warm does it have to get until you run into problems? And can it be too warm to ski?
As the weather warms up going into the spring months the higher temperatures affect the snow and the condition of the runs. The typical crystal structure of snowflakes changes to make a variety of different snows, meaning it can be slushy depending on the temperature. Most northern hemisphere resorts end in April or May, but a few continue summer skiing courtesy of glaciers that provide year-round skiing.
While this spring weather means you don’t have to wear so many layers and you can enjoy your lunch out on a terrace, the downside is that the snow may not be ideal to ski on.
What Happens To Snow When The Weather Starts To Warm Up?
Resorts vary considerably in how late during spring they close. Usually, the altitude of the resort is a major factor. For every 1,000 feet, you climb the temperature drops by 5.4 deg F° (For every 1,000 m you climb the temperature drops by 9.8 deg C°).
So, put simply, higher resorts can stay open later in the spring because they experience lower temperatures because of the altitude. Other factors affect spring resort closure too such as microclimates, the prevailing weather, and how shaded the runs are.
Typically, as spring approaches, daytime temperatures can rise well above freezing during the daytime, where the warmth is enough to start thawing the snow. Generally, the thaw is a slow process, partly because the lying snow holds a lot of stored latent energy, which will require a considerable amount of sunlight to melt it.
Additionally, by its nature snow is brilliant white, which means sunlight is reflected off it rather than being absorbed, which slows the thaw of the snow. During the night in these early days of spring, the temperature still falls below freezing regularly, meaning the part melted snow from the daytime is frozen into ice during the night.
For new snow that falls during the spring months, the atmospheric temperature needs to be below 0°C (32°F), while the ground temperature needs to be below 5°C (41°F). The atmosphere must also contain enough moisture to start precipitation.
This process continues day after day and is called freeze-thaw. For skiers, this repeated cycle of temperature changes affects the texture and structure of the snow crystals into distinct forms:
1. Slushy and Wet Snow
When snow repeatedly melts and refreezes the tiny crystals that make up snowflakes melt and form into larger ice crystals during the freezing temperatures of the night. The following day these larger ice crystals break up and float, surrounded by water.
Slushy, wet snow is most often found at the bottom of the lower lifts in spring, where the higher temperatures and high footfall have contributed to pulverizing the wet snow. Slushy and wet snow is very difficult to ski in, partly because the ski isn’t well supported and so tends to sink in, and partly because it’s just physically difficult to maneuver the skis through the wet, heavy slush.
Another physical problem associated with skiing through slush is that the liquid water tends to adhere to the base of the ski, making them feel heavy to use and difficult to make progress with them. If you fall over in slush, you’re in for a thorough soaking and even a few minor abrasions from the ice crystals.
2. Sticky Snow
Sometimes, as the warmer months approach snow falls through the higher up freezing air, but then falls to ground level, where the air is above freezing. This causes the snowflakes to partly melt before landing on the snow layer. These partially melted snowflakes are very sticky and will coat anything they land on.
Sticky snow is about two or three times as dense as normal snow, with its higher water content, making it very difficult to ski over. In a similar way as slushy snow, sticky snow can also adhere to the base of the ski with its fine wet texture. This excludes all air and creates a high coefficient of friction, meaning it is difficult to push the ski over the snow surface, while progress down runs feels like it’s in slow motion.
While sticky snow is great for snowballs and snowmen it can cause real danger when it falls on power lines, large branches, and even flat rooftops, which have been known to collapse from the weight.
3. Freeze-Thaw on Icy Runs
Another symptom of warmer spring weather is the arrival of freeze-thaw on icy runs. This isn’t too bad on groomed runs, where the snow is flattened out and broken up. However, an ungroomed run, which has partly melted during the afternoon and then refrozen overnight is very difficult to negotiate.
The snow will be hardpacked already, after being compacted by the previous day’s skiers but then thawing and refreezing will additionally have frozen the surface solid. During the morning it will slowly thaw and create a covering of small balls, which look like corn kernels and hence its slang name, corn. Generally, runs like this are best left till later in the morning when the snow has softened.
The freeze-thaw cycle can also generate patches of ice on runs. Typically, these patches are made of really compacted snow rather than clear ice, however, they are just as difficult to negotiate as the real thing.
Most skiers don’t like ice, as it is difficult to control and very unpredictable. Trying to get your ski edges to bite into the icy surface is usually very difficult.
If you experience a patch of ice and find it impossible to get your edges to bite, then often the best advice is to just get across the patch of ice anyway you can, and then when you reach snow again take control once more.
Alternatively, if you see negotiating ice as a challenge to be conquered find a wide-open, smooth patch, where you can practice your technique safely.
What Happens When The Weather Generally Warms Up in Spring?
As the winter season gradually comes to an end in April and May resorts manage the change in the weather by closing runs, which have the poorest spring snow. Allowing skiers to concentrate on the runs, which still have quality spring snow.
This process of shutting down enables resorts to save costs on lifts, staffing, and grooming, which is vital as the number of skiers rapidly diminishes.
As the weather warms the snow thaws eventually leaving ribbons of snow to ski down, while the snow will become more and more granular and slushy, as a product of freeze-thaw conditions. Some skiers are enthusiastic about skiing in late spring when the sunny weather, heavily discounted accommodation, and lift tickets more than makeup for the lack of powder.
It’s Never Too Warm for Skiing in a Few Resorts
By a quirk of geological fate, a few ski resorts around the world are linked to glaciers, which with their thick layer of ice can support the snow layer which lies on top. The frozen thermal energy of the glacier ice ensures that even during the warmest sunny day the impact on the snow will be minimal.
Even so, it’s not unusual to find snowbanks, collected by snowploughs, which are then covered with thermal sheets to reflect the heat of the sun. If runs then need a top-up this snow can be ploughed where it’s needed.
Timberline Lodge has the longest ski season in North America with some great summer glacier skiing close to Mount Hood. It has a dedicated chairlift which only operates during the summer, as it is too snowy and windy during the winter.
In Europe, the Matterhorn Glacier Paradise is part of Zermatt in Switzerland, while the Hintertux Glacier is close to the resort of Mayrhofen in Austria. These are now the only two year-round summer skiing destinations in Europe. It’s not unusual to bump into Olympic athletes as they train at altitude.