During skiing, we will face some weather hazards. Temperature and wind speed are the main factors to form these hazards.

Temperature:
For skiers, the typical skiing temperature should be approximate -8℃ to 3℃. In other ways, too warm or too cold weather that is caused by the frontal system is not suitable for skiing.

TOO cold temperature:

The cold front is always the main reason causing colder temperatures. When it passes, the temperature will decrease dramatically. Since the cold front is advancing when it meets the warm front, it is often accompanied by precipitation, snow, fog, and other weathers, which lead to bad visibility and thus influence skiers’ judgment on the direction. Colder temperatures can increase the risks for skiers to get wind chill or hypothermia, which is making it painful and harmful to your body. Therefore, when the temperature is below -50 degrees, you should be sure to cancel the ski trip.

What is wind chill?
The body temperature drop due to the flow of cooler air. Wind chill accelerates the rate of heat dissipation in your body. So, it will eventually induce frostnip, frostbite.

Frostnip:
Your skin may become pale or red and feel extremely cold or numb. Then, you may experience a warm feeling on your skin and it might look blotchy or purple, and appear fluid-filled blisters. 

Credited to Laurence D., accessed 2017

Frostbite 
During this stage of frostbite, your skin will begin to change from a light red color to a pale color. If you touch your skin, you may feel it is hard and cold. After a while, your skin will begin to feel warm, like frostnip, and swollen. 

Credited to Laurence D., accessed 2017

How to avoid or treat frostnip and frostbite?

Before skiing, you need to prepare cold, windproof, and waterproof clothes. Moreover, bringing a scarf, hat, and gloves is also significant since they can protect your extremities. Always change wet socks to keep your feet dry. If you are getting frostnip or frostbit, putting a cloth or towel between the ice pack and your skin. Furthermore, remember that drinking is not a good method to release frostnip or frostbite. Some people believe that drinking alcohol will warm their bodies. But it was scientifically proven that drinking in cold weather can cause you to lose heat more quickly.

 

Potential hazard---surface hoar

The extremely cold temperatures can cause avalanches due to the unstableness of the layer. When the air temperature falls below the frost point temperature, the water vapor above the snow surface will directly deposit into ice crystals on the snow surface and form a surface hoar. This phenomenon always happens with light wind at night but keeps forming into the daytime on a shady slope. It is beautiful but also is fatal to the skiers. When new snow layer forms above the surface hoar, a weakly bounded snowpack, the "sandwich form" snow layers will cause large-scale avalanches and thus put skiers in danger. It is mainly because the snow that falls on top is weakly bonded to the snowpack beneath over a widespread area.

 

More information about the cold front:

Although cold front always accompanies some bad weather and result in some potential hazards, it is not entirely disadvantageous to skiers. Right-side-up snow, which forms along with a cold front and under the colder temperature, is good for skiing because the vertical density gradient tends to lift your skis or snowboard. In other words, it has a lower-density snow layer of higher density snow layer, therefore is less tends to occur avalanche. Therefore, skiing in the right-side-up snow is favorable for the skiers.

 

Too Warm temperature

By contrast, the warm front can increase the temperature since its warm front is advancing. Unlike the cold front, temperature changes in a warm front are slower because the horizontal temperature gradient is weaker. Under the high temperature and strong insolation, skiers can suffer hypothermia, sunburn, and snow blindness.

How to avoid or treat hypothermia and sunburn?

In warmer temperatures, skiers should wear thin, loose, and long-sleeved clothes. In addition, skiers should apply as well as bring suncream. In terms of equipment, it is essential to wear glacier glasses or a hat to minimize the effect of snow blindness. Without them, you will feel a burning or gritty sensation in the eye due to strong sunray.

Credit to Elliott Gaynor, accessed July 16, 2017

The misconception about the warm front is that it always brings good weather and higher temperature. Unarguably, a warm front will heat the air; however, it does not always along with clean skies. In fact, the upside-down snow that appears along with the warm front has higher density snow overlying lower-density snow. Due to its structure, snow layers are unstable and easy to generate avalanches.

 

Wind

Wind direction is another vital factor that affects safety and ski conditions. Skiers need to consider pressure gradients since they are the main factors that determine the wind direction. Typically, clam wind is the optimal wind speed for skiing and appears in the high pressure system. The characteristics of high pressure system are associated with dry conditions, clear skies. But, it does not imply skiers are safe under the high pressure system. The wind direction of high pressure system rotates clockwise north of the equator and counterclockwise south of the equator. Under this anti-cyclone flow, the wind locks up the air mass, thus the weathers, such as fog, rain, and snow, are hard to form in the sky. On the contrary, a lower pressure system causes the presence of a frontal system and brings many bad weathers that are mentioned before. It will either influence skiers’ visibility or their health. Furthermore, the wind speed can also influence the ski trip. Skiers will get wind chill and be hypothermia if they ski under a high wind speed. The specific symptoms and treatment are mentioned above. To avoid this situation, you need to know where is the wind-exposed location. The wind speed is relevant to the altitude, the higher altitude has less friction slows down the wind. By contrast, slope and valley are awesome wind-sheltered location which is good for starting your ski trip.

Credited to wwhsta. com

 

Visibility

Fog and clouds in the valley are relevant to visibility, which is also vital to your safety. They are formed under high relative humidity and related to radiative cooling and high pressure system. Due to the high pressure system, the sky is clear at night which strengthens a temperature inversion and enhances the impact of cold-air pooling. The main hazard of fog and clouds in the valley is limiting visibility. It is not only difficult for you to recognize the ski track, but it's prone to losing your ways and getting separated from your friends.

Snow density

The snow density is inextricably linked to temperature and wind. Notably, the relationship between those two factors and snow density are both proportional. It indicates the higher temperature implies higher water composition and higher density of the snowpack. Therefore, the warmer the temperature is, the higher the snow density is, and versa vice. Similarly, the snow density will become higher if the wind speed is faster while the lower snow density often occurs under the slower wind. It is essential to learn the snow density because it possesses the potentiality of inducing avalanche danger. The presence of unstable snowpack is led by upside-down snow. As well as its name, simply, it illustrates that higher-density snow is overlying lower-density snow. Unarguably, the low-density snowpack is unable to withstand the pressure of the higher-density snowpack on top, thus avalanches are easier to occur. As a skier, right-side-up snow is a good condition for you to enjoy your skiing since a lower-density snow layer is on top of the higher-density snow layer. 

Avalanche

Undeniably, avalanches are the most dangerous weather hazards for skiers. They can be divided into two basic types, sluff avalanches, and slab avalanches. The sluff avalanches include wet sluff and dry sluff and are made up of surface or near-surface snow that is not well-bounded. Though the damage of this type of avalanche is small, it still processes the possibility to trap people. Another type is called slab avalanches( dry slab & wet slab). It occurs when a layer somewhere fails to beneath the surface layer and the cohesive layers above fracture a block and slide downhill. It generates a large scale of avalanches and people are easy to be buried by the snow.

Sluff avalanches, Credited to Boris Štupar, accessed November, 11th, 2008

Slab avalanches, Credited to SnowBrains. com, accessed November 12, 2014

A graph that might help you identify different types of avanches

Type	comprised of loose snow	comprised of cohesive blocks	Likely to knock you off your feet	Likely to bury you	Occurs due to layer failure	Layer failure due to melt or rainwater	Begins at a joint and fans out	Fracture propagates across slope
Dry sluff	✔		✔		✔		✔
Wet sluff	✔		✔		✔	✔	✔
Dry slab		✔	✔	✔	✔			✔
Wet slab		✔	✔	✔	✔	✔		✔

the information table is originated from 7f Stable & Unstable Snowpacks (ubc.ca)

 

Reference:

The above information is sourced from UBC ATSC 113 Snow Sports Weather Module, accessed 2021 Links to an external site.

Wind chill index - Canada.caLinks to an external site.

Frostnip: Definition, vs. Frostbite, Pictures, and Recovery Time (healthline.com)