Module 1 | Scenario 2: Snow Water Content

  • Due Jan 12 at 11:59pm
  • Points 10
  • Questions 5
  • Available Jan 6 at 12am - Mar 26 at 11:59pm
  • Time Limit None
  • Allowed Attempts 2

Instructions

Overview

The density of snow depends on its water content — the percentage of the snow that is frozen or liquid water. What skiers call "light" or "dry" snow has a low water content, typically less than 7%, whereas "heavy" or "wet" snow has a high water content, typically 11% or greater.  

In this learning activity, you use observations from Alta Ski Area to determine the water content of freshly fallen snow and how it has evolved during a major storm cycle. After completing the learning activity you should be able to calculate the water content of snow from observations of new snow depth and snow water equivalent. You should also have a greater appreciation for the importance of these observations for avalanche hazard.

Instructions

Utilize the information located in the Scenario and Key Concepts to answer the questions located in this activity. You may refer to your textbook and notes to help you work through the assigned questions if desired. You will have two attempts to complete this activity. The highest grade will automatically be recorded. Once you have submitted your activity for a second time, you will be able to see the correct answers. Discuss with your instructor if you have questions about your answers or feedback.

  • Activity is due Sunday, by 11:59 p.m. MT

Submission and Assessment Guidelines

  • You will complete the quiz associated with this scenario within Canvas. For help on how to take a quiz in Canvas, review how do I take a quiz.
  • This learning activity is worth 10 points toward your final grade.

Scenario

From February 5-7, 2020, the Wasatch Range experienced heavy snowfall and strong winds that led to widespread natural avalanche activity. The excerpt below from the February 8, 2020, Utah Avalanche Center forecast for the Salt Lake Area Mountains highlights the severity of the situation, with many large avalanches crossing the highway in Little Cottonwood Canyon.  

Utah Avalanche Center Report excerpt: Dave Richards from the Alta Avalanche Office just recorded the longest period of sustained westerly winds in their history. Wind, combined with heavy snowfall created a massive natural and explosive triggered avalanche cycle in Little Cottonwood Canyon. Many large avalanches crossed the closed highway leaving behind huge debris piles with large trees. Tanners, Whitepine Chutes, Cottonwood Draw, Superior, and Toledo bowl we among the largest of the reported avalanches that crossed the closed highway. Alta also reported an explosive triggered avalanche that broke into old snow on a north facing slope at 10,700' in elevation. The crown was 6' deep. In the backcountry, observers still noted the upside down structure to the snowpack and many of them gave avalanche terrain a wide berth and stuck to low angled terrain.

The video below from the Utah Department of Transportation illustrates the severity of the avalanche cycle: 

During the storm, Alta Ski Patrol measured 9 inches of new snow with 0.86 inches of snow water equivalent on February 5, 19 inches of new snow with 3.54 inches of snow water equivalent on February 6, and 5 inches of new snow with 1.12 inches of water equivalent on February 7.  

Key Concepts

Snow water content is the ratio of the snow water equivalent to the snow depth expressed as a percentage. Recall that snow water equivalent is the depth of water you would have after the snow melts. To calculate snow water content we use:

snow water content = (snow water equivalent / snow depth) x 100

then add the percent sign (%).

Citations

Overview:

Alta

      • Citation: Alta. (n.d.). Alta. 

Scenario:

Forecast for the Salt Lake Area Mountains

      • Citation: Meisenheimer, T. (2020, February 8). Forecast for the Salt Lake area mountains. Utah Avalanche Center 

Little Cottonwood Canyon Avalanches - Feb 2020

      • Citation: Utah Department of Transportation. (2020, February 14). Little Cottonwood Canyon avalanches - Feb 2020 [Video].
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