Unexplainable

Snow day!

March 11, 2026

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  • A snowflake's shape is a record of its unique path through the atmosphere, determined by temperature and water vapor content at different points. 
  • The crunching sound of snow occurs when walking breaks the fragile connections (sintering bridges) formed between snow crystals that are close to their melting point. 
  • Fresh, loosely packed snow absorbs sound because the air pockets between the crystals muffle sound waves that are not reflected back. 

Segments

Snowflake Formation and Shape
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(00:05:10)
  • Key Takeaway: Snowflake shape is a record of its atmospheric journey, influenced by temperature and vapor content.
  • Summary: Snowflakes form around a condensation nuclei, growing into shapes like dendrites or columns based on atmospheric temperature and water vapor content. The final shape reflects the varying conditions the crystal encountered as it moved up and down within the cloud. Hitting other snowflakes can cause aggregation, resulting in larger, messier structures.
Snow Crunching Science
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(00:07:26)
  • Key Takeaway: Snow crunches when walking breaks fragile connections formed by sintering between crystals.
  • Summary: Snow on the ground is a pile of crystals with air between them, similar to a feather pillow. Because snow is near its melting point, crystals undergo sintering, attaching to each other by forming fragile bridges. The crunching sound is the physical breaking of these sintered connections under pressure.
Sound Absorption by Snow
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(00:09:39)
  • Key Takeaway: Newly fallen snow absorbs sound due to loosely packed air pockets before sintering occurs.
  • Summary: Snow absorbs sound most effectively right after a new snowfall when crystals have not yet sintered. The structure consists of loosely lying snowflakes with significant amounts of trapped air between them. Sound is muffled as it enters these air pockets instead of being reflected back to the ear.
Factors Affecting Snow Texture
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(00:10:26)
  • Key Takeaway: Snow stickiness and fluffiness depend on storm temperature, with warmer snow being better for building.
  • Summary: The texture of snow varies based on the conditions during the storm, starting with how the crystals grew in the atmosphere. Colder storms produce dry snow unsuitable for snowballs, while warmer snow (above -3 degrees C) has more liquid water, making it sticky and ideal for building snowmen. Stickiness increases significantly as the temperature approaches 0 degrees C.
Snow Accumulation Physics
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(00:12:00)
  • Key Takeaway: Snow stacking height on surfaces like branches is maximized when snow is warm enough to sinter and stick.
  • Summary: The ability of snow to stack high on surfaces depends on the snow temperature, particularly when it is close to the melting point. Warmer snow allows snowflakes to sinter and adhere to each other and to surfaces like tree branches. Liquid meltwater refreezing also helps the snow structure adhere firmly to objects.
Environmental Benefits of Snowpack
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(00:13:39)
  • Key Takeaway: Snow acts as an excellent insulator, protecting soil, plants, and animals from extreme cold.
  • Summary: Snow’s trapped air pockets provide insulation, creating a significantly warmer environment beneath the snowpack than the air above it. Animals often use this insulation to hibernate or build dens, and plants with shallow roots are protected from root damage during severe cold. Years with less snow often result in colder conditions for hibernating life.
Water Resource Prediction Challenges
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(00:18:05)
  • Key Takeaway: Measuring mountain snowpack for water resource prediction is difficult due to terrain variability and spring water loss.
  • Summary: Snowmelt in the Western US is a crucial water source, making accurate measurement of mountain snowpack vital for water rights and agriculture. Snow pillows (SWE measurement devices) provide localized weight data, but terrain variability makes extrapolation difficult. Springtime warming causes plants to transpire water before it reaches streams, leading to streamflow being lower than snowpack surveys predict.
Snow vs. Rain Predictability
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(00:23:46)
  • Key Takeaway: Snow provides greater long-term water predictability than rain because it stores water until melt season.
  • Summary: Warmer temperatures cause more precipitation to fall as rain rather than snow, impacting predictability. Rain runs off immediately, offering no long-term storage for summer use. Snow, by storing water on the hillside, provides crucial predictability for summer water availability that rain forecasts lack.
Researcher’s Memorable Snow Encounter
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(00:24:47)
  • Key Takeaway: Ptarmigan birds were observed erupting from beneath light, fluffy snow where they were hiding.
  • Summary: The snow scientist recalled a project in Gothic, Colorado, where researchers accessed a remote mining town by skiing in. While leading a group through light snow, she disturbed a flock of ptarmigan that were buried underneath for insulation. The sudden eruption of white birds from the snow was described as a beautiful and magical event.