Avalanche Climate
Knowing your region’s climate is important, particularly when forecasting for a new area, for it gives you an idea of the:
- Types of weather to expect
- Average winter temperatures
- Average kind of snow that falls
- Types of avalanches that may occur
The three major climate types are described below.
Maritime (coastal) avalanche climate
- Deep snowpack with settled mid-winter snow depths of 9 feet (3 m) or more
- Frequent storms produce moderate to heavy snowfall
- Relatively mild regime throughout winter, producing a denser snowpack
- Often rains on the snowpack throughout the winter
- Consistent and relatively mild air masses along with more frequent storms create more consistent snowpack compared to the other climates
- Usually has direct-action avalanches
Continental avalanche climate
- Relatively shallow snowpack with settled mid-winter snow depths less than 5 feet (1.5 m)
- Less frequent storms with lower-density snow than the maritime climate
- Long periods of drought with very cold temperatures during winter
- Temperatures variable throughout winter, leading to more varied layers within the snowpack
- Both direct action avalanches and delayed-action avalanches are common and often involve layers deep within the snowpack; the pack can remain unstable and avalanches may be triggered even weeks after last significant storm
Intermountain (transitional) avalanche climate
- Intermediate mid-winter settled snow depths ranging from 5 to 9 feet (1.5 to 3 m)
- Storms are more frequent and dry periods are not as prolonged as in continental climates
- Temperatures are closer to maritime climate but have less frequent rain events
- Both direct- and delayed-action avalanches can occur and sometimes involve deep layers
Note that interior ranges can assume the characteristics of a maritime climate during unusually warm and wet winters, while coastal ranges can have a continental-type climate during unusually dry and cold winters. In addition, avalanche climates can change with elevation within an individual mountain range, going from an intermountain climate at lower elevations to a continental climate much higher up. This is common when large disparities in elevation over short linear distances exist.
The highlighted row of the table summarizes the relationship between climate and avalanche potential.
Think back on the Glory Bowl Avalanche. What type of avalanche climate does this part of the Tetons in Wyoming have? (Choose all that apply.)
Both A and B are correct.
Generally, the area’s elevation and inland location give it an intermountain climate. However, the early season conditions and shallow snowpack give it characteristics of a continental climate.