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Don’t get confused about snow level and freezing level

Anyone interested in winter recreation cares deeply whether they are in rain or snow, snow generally being preferred, of course. So it is important to know the current and future elevations of the snow level, the height separating snow from rain.

And there is another closely related term that is used in weather forecasts: the freezing level, the altitude at which the temperature drops to freezing.

Freezing level: The freezing level is the elevation at which the temperature drops to 0°C. As the snow falls from the colder upper atmosphere into the warmer air below, it often reaches a level at which temperature warms to freezing (0 degrees C), the freezing level.

Snow level: Snow levels is lower than freezing levels because snow can still fall at temperatures slightly above freezing. The elevation where the snow turns to rain is the snow level. It takes time for the snow to melt, and that is why we will often see precipitation falling as snow even when it is +1°C or +2°C (and sometimes even more) at the surface. If the snow level is above the ground, it will still be lower than the freezing level as snow often takes a few hundred metres to melt as it falls toward the ground.

Both the freezing level and snow level can change in time as precipitation falls, and the direction is usually down. The reason? Cooling due to evaporation and melting.

First, evaporation: The air below the cloud is often unsaturated, which means the relative humidity is less than 100%. As the snow falls into that layer there is evaporation (actually sublimation), which results in cooling. If the snow turns into rain there still can be evaporation and cooling. Such cooling continues until the air is saturated, and can cause the freezing and snow levels to drop quickly and substantially (hundreds to even thousands of feet).

And then there is melting: When snow falls into air warmer than freezing, it melts. But it takes energy to melt the snow, and thus as melting occurs the surrounding air cools. Heavier precipitation results in more melting and more cooling. Such cooling can occur even after evaporation has stopped (because the air becomes saturated). Melting thus causes the freezing and snow levels to fall. The good news about this: If you are up in the mountains and it starts to rain on you, there is a good chance, particularly if you are near the snow level, for the rain to turn into snow!

What is wind chill factor?

The Wind Chill Factor is commonly referenced in weather reports. However, few of us have a firm grasp on the meaning. Wind chill is the meteorological term used for explaining how the wind can make us feel even colder (chillier) than the actual temperature. Basically the Wind Chill Factor describes how cold you will feel when you step outside when the temperature is below 10°C and the wind speed is above 4.8kph. On a more scientific term the Wind Chill Factor is a measurement of the total conductive heat transferred from the skin due to a cold wind. The Wind Chill Factor is not an exact measurement as the actual Wind Chill Factor would truly be different for every body type and the specific clothing being worn.

On average, our bodies are 37°C and they go to great lengths to maintain that temperature. If our body temperature goes too far in either direction we can begin to show signs of hypothermia, heat exhaustion, or heat stroke.

The wind chill factor is a measurement of the wind’s affect on our bodies heat transfer during the winter. Unlike the summer, when our bodies are trying to release heat, during the winter our bodies desperately try to hold onto the heat.Higher wind speed combined with lower temperatures means more heat is removed from your body and the air around your body is replaced with colder air. The critical concept here is that the actual outdoor temperature does not change by an increased wind speed. Instead it is the amount of heat removed from your body that changes.

It is important not to think of the wind chill factor as something in your head. The wind chill factor is a physical process that can lead to a dangerous situation. For example, the removal of heat from your skin can result in an internal body heat loss. As the process continues and your internal temperatures drop, hypothermia can develop.

Wind Chill Temperature is used to measure the Wind Chill Factor. Wind Chill Temperature is then a summation of the outdoor temperature and the cooling effect of wind.

Wind Chill (°C) = 13.12 + 0.6215(Air Temperature °F) – 11.37x(Wind Speed in MPH*0.16) + 0.3965x(Air Temperature °F)x(Wind Speed in MPH*0.16

When you hear the wind chill factor, it is safest to assume that the wind chill temperature is the temperature for which you should prepare. Take steps to avoid heat removal by wearing several layers of dry clothes with layers of air in between. Aside from clothing there is always location and movement. Try to get in line with the warm rays of sunlight and take shelter from cold winds which will only remove the recently gained heat. Additionally, keep your body moving so more heat can be produced. You’ll notice how quickly you cool down when you stop moving after activity. Try eating high protein/energy foods such as nuts, energy bars, chocolate etc and drink hot drinks – even hot water with a dash of cayenne pepper is known to provide an instant heat spike that will help your body glow in the cold.

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