It’s not just that Jack Frost is nipping on your nose, frost can be a deadly factor in the backcountry.
Frost is simply winter’s dew. Icy crystals form on exposed surfaces when the air temperature drops below freezing and water vapor in the air condenses.
Hoar frost is made up of large ice crystals that develop when surface temperatures are below freezing. These crystals cover the surface and can be found on top of old snow, on tree branches, or exposed rocks.
Surface hoar is the icy crystals that sparkle and shimmer on top of snow banks. You’ve probably seen this dozens of times on early morning ski trips. It is the most common type of hoar frost.
What has hoar frost got to do with outdoor adventures in the backcountry?
When surface hoar is buried by new snow, the hoar frost crystals may not bind strongly to the new snow layer. These crystals can also collapse and provide a good sliding surface for upper snow layers. On steep slopes, these weak layers are often responsible for avalanches. Buried surface hoar can remain unstable for up to several months.
What can you do about it?