The Snow Booklet

A guide to the science, climatology, and measurement of snow in the United States

Nolan J. Doesken
Arthur Judson

ISBN #0-9651056-2-8 (2nd Edition)

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Colorado Climate Center
Department of Atmospheric Science
Colorado State University
Fort Collins, CO 80523-1371

• US Department of Interior, Bureau of Reclamation, Flood Hydrology Group
• NOAA, National Climatic Data Center
• USDA, Natural Resources Conservation Service, Snow Survey and Water Supply Forecasting Program
• CSU Agricultural Experiment Station

Nolan Doesken:

Nolan Doesken's love for snow developed at an early age. As a child, he could not sleep at night if snow was falling or predicted. Much of Doesken's appreciation for snow came from his years as a paperboy in a small town in central Illinois. "I particularly remember a Sunday morning in March or April when I awoke to an unexpected four inches of snow. The temperature was close to 32 degrees Fahrenheit, so I figured the snow would be heavy and wet. But, to my amazement, it was like goose down. As I loaded my papers, a car drove past the house at a low speed. A cloud of fluff lifted into the air and when the car was gone, the street had been blown clear. That's when I learned that the ten to one 'rule' didn't always apply." Since 1977, Doesken has been the Assistant State Climatologist at the Colorado Climate Center at Colorado State University. He also is a National Weather Service cooperative observer. Doesken closely works with National Weather Service personnel to improve the quality of weather data for climatic applications.

Arthur Judson:

Snowbursts that frequented his father's logging camps on Tug Hill, New York, fascinated Art Judson. As a young Marine, he chased snowstorms in California's San Bernadino mountains, then found deeper snows in the Rockies and Cascades. After obtaining a B.S. in Forestry from Oregon State University in 1960, he started chasing avalanches as a Forest Service snow ranger in Colorado. He later became a career avalanche forecaster and snow scientist with the Forest Service Avalanche Project. "Jud," as he is known to his friends, organized a special network to provide weather, snow, and avalanche data for avalanche forecasting and warning across the mountainous West. He founded Colorado's Avalanche Warning Program, developed an avalanche forecasting model, and worked to establish a warning service in Alaska. Currently, Jud lives in Steamboat Springs, Colorado (average annual snowfall 171 inches with 300-600 inches falling on the nearby mountains), where he continues to enjoy snow greatly.

• Preface
• The Power and Beauty of Snow
• The Science of Snow
  • What is snow?
  • Characteristics of fresh snow
  • Snow on the ground
  • Melting snow
  • Brief primer on avalanches
• Climatology of Snow in the United States
  • Storm tracks
  • Snow frequency
  • Snowiest U.S. weather stations
  • Snowfall duration and intensity
  • Snowfall seasonality
  • National snowfall patterns
  • Snowfall variability
  • Snow hydrology and snowloads
  • Record snowstorms
• Measuring Snow
  • Historical perspective
  • Elements of snow observations
  • Instruments for measuring snow
• Problems and Challenges in Measuring Snow
  • Impact of inconsistent data collection
• Procedures for Measuring Snow
  • Basic preparations
  • Taking observations
  • Snowfall
  • Depth of snow on the ground
  • Precipitation
  • Water content of freshly fallen snow
  • Water content of snow on the ground
• Dealing With Adversity
  • The big blizzard
  • The day the snow wouldn't stick
• Common Questions About Snow
• Bibliography
  • Other suggested readings
• Data Sources
• Snow Glossary
• Credits and Acknowledgements
• Snow Memories

• Based on 1961-1990 National Weather Service records, Rochester, New York, is the snowiest large city in the United States (population greater than 200,000) averaging 94 inches of snowfall annually. Buffalo, New York, is a very close second.

• Approximately 70 percent of the annual snowfall in the United States falls during December, January and February. However, for areas near the eastern slopes of the Rocky Mountains, March and April are often their snowiest months.

• On average, 105 snow producing storm systems hit the lower 48 United States annually.

• The old saying that ten inches of fresh snow contains one inch of water is only occasionally true. In reality, ten inches of new snow can contain as little as 0.10 inches of water to nearly four inches.

Three properties of snow are responsible for most of the difficulties in making accurate and consistent measurements.

1. Snow often melts as it lands or as it lies on the ground, both from warm soil below or from warm air, wind, or sunshine above. As a result, the observer may be in a dilemma. The observer may wonder, "It snowed for three hours, but there is nothin g on the ground. Do I report zero or a trace, or do I make something up?"
2. Snow settles as it lies on the ground. Depending on the initial density of fresh snowfall and on other coincident weather conditions, the snow may settle rapidly or very gradually. This can have profound effects on observations. Observers who me asure more often than once each day may report much more snowfall than a once-daily observer.
3. Snow is easily blown and redistributed. It tends not to land or lie uniformly on the ground, but instead forms deep drifts in some areas while exposed areas may be blown completely clear. A related problem is precipitation gauge catch. Even at r elatively low wind speeds, snow is easily deflected around the top of precipitation gauges. Most winter precipitation measurements using standard precipitation gauges underestimate the precipitation that actually fell and sometimes by large amounts.

Two crucial issues in measuring snowfall accurately are:

1. determining a representative location for measuring snow, and
2. establishing a consistent time interval between measurements of the depth of freshly fallen snow.

For example, an observer who measures new snow accumulation very frequently, and each time clears the snowboard to begin a new accumulation, will report snowfall totals that exceed what has actually accumulated on the ground. Frequent observations (hourly or every few hours) may be very useful for evaluating the intensity of snowfall, but these incremental measurements cannot be added together to give a meaningful snow accumulation.

For purposes of climatological comparison, what is reported as snowfall should be the maximum measured accumulation of new snow since the previous day.

1. Measure the amount of snowfall for the previous 24 hours from a snowboard in a representative location or from an average of several measurements.
2. Measure the total combined depth of old and new snow on the ground.
3. Measure the precipitation that has accumulated during the past 24 hours in a properly exposed precipitation gauge.
4. Measure the water content of new snow that has accumulated on the snowboard (if representative) during the previous 24 hours.
5. Measure the total water content of both old and new snow on the ground.
6. Record all data using consistent and documented units.

National Weather Service Snow Measurement Guidelines

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