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What Backcountry Users should know about SNOTEL

What Backcountry Users should know about SNOTEL. Jeff Anderson Hydrologist NRCS Snow Survey Boise, ID. jeff.anderson@id.usda.gov 208-378-5740. Outline. What is a SNOTEL? Snow Survey Background SNOTEL Data Accessing Data Tips for Interpreting Data What’s up with those -99.9’s?.

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What Backcountry Users should know about SNOTEL

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  1. What Backcountry Usersshould know about SNOTEL Jeff Anderson Hydrologist NRCS Snow Survey Boise, ID jeff.anderson@id.usda.gov 208-378-5740

  2. Outline • What is a SNOTEL? • Snow Survey Background • SNOTEL Data • Accessing Data • Tips for Interpreting Data • What’s up with those -99.9’s?

  3. Typical SNOTEL in Summer

  4. Same SNOTEL in Winter 16 ft gage April 22, 2011 Crater Meadows SNOTEL, Clearwater Basin, Idaho

  5. Why is the government interested in measuring snow? In 1935, as a result of the dust bowl, Congress told the Department of Agriculture to… “Conduct snow surveys for the purpose of forecasting irrigation water supplies, and to develop uniform equipment and methods for snow surveying and water supply forecasting.”

  6. Glory Days… Until the late 1970’s snow measurements were done by hand once a month at 1,600 snow courses across the West.

  7. In the 1980s SNOTEL started collecting data automatically using Meteor Burst Communication 50 miles above the ground

  8. Today, hourly SNOTEL data is on the internet but... Just Seems in reality most days we sit in a cubical looking at a computer just like everybody else.

  9. That’s not true every day though…

  10. Snow Water Equivalent (SWE or WTEQ) Weight of frozen water(Snow & Ice) Take Home 0.1” new SWE = 1” snowfall Weight of liquid water

  11. SWE doesn’t change as the snowpack settles

  12. Where would you put a Avy Weather Station? Ideal Avy Weather Location North Aspect High Elevation Exposed to wind Close to ski terrain 7800ft 1 Best Avy Weather Locations 2 3 7800ft Green & Yellow = ski slopes Red = skin tracks

  13. 1 Pilots Peak January 22, 2011 Site 1 shown in previous map

  14. Ideal SNOTEL Location North Aspect Mid-Elevation Not exposed Vehicle access 7800ft 7800ft Mores Ck Summit SNOTEL (6100ft)

  15. SNOTEL dataSWE, Snow Depth, Precipitation, Temperature, Wind

  16. http://www.wcc.nrcs.usda.gov/snow/

  17. Daily Data

  18. -99.9 = Full Scale = it’s probably snowing Full Scale Values Anything that stops the sound pulse from making a return trip from sensor to the ground (snow) and back can cause a full scale value. Examples include: Wind, new light powder, falling or blowing snow, fog, rime on sensor, etc…

  19. -99.9 = Full Scale = it’s probably snowing Full Scale Values The snow depth sensor uses a sound pulse to measure the distance to the ground (or snow). Anything that stops that sound pulse from making a return trip from sensor to the ground (snow) and back can cause a full scale value which is replaced by a -99.9 in SNOTEL reports. Wind, new low density snow, falling or blowing snow, fog, rime on sensor, etc… are common reasons the sensor fails to make a reading.

  20. FAQ http://www.id.nrcs.usda.gov/snow/faq/

  21. Hourly Data

  22. Daily vs Hourly

  23. Daily data

  24. “Flutter” makes hourly data confusing Hourly “flutter”

  25. My watch says 7:20am why is current SNOTEL data from 6:00am? All SNOTEL time stamps are Pacific Standard Time. That means… During most of winter Southern Idaho is 1 hour behind and Oregon is OK. During daylight savings time Southern Idaho is 2 hours behind and Oregon is 1 hour behind. Some SNOTEL sites aren’t good reporters and can be multiple hours behind.

  26. Other ReportsWindRate of ChangeOther hourly report

  27. Other products SNOTEL Wind Data* Ideal SNOTEL Location North Aspect Mid-Elevation Not exposed Vehicle access Vienna Mine SNOTEL Sawtooths (above Smiley Creek Lodge) In cirque 8960ft

  28. SNOTEL Wind Data* Vienna Mine SNOTEL Sawtooths (above Smiley Creek Lodge) In cirque 8960ft Even Light winds here will mean wind slabs at ridges

  29. Wind Products Drifting Snow occurs when BFF (BeauFort Force) > 4 or windspeed >15mph

  30. http://www.id.nrcs.usda.gov/snow

  31. Rate of Change Reports

  32. Regional Hourly Reports

  33. Conclusions • SNOTEL is largest mountain weather monitoring system in the world • SNOTEL network set up for water resource needs, not avalanche forecasting • Daily data gets human QC, often less confusing • SWE data often more reliable than snow depth data, or can be used in lieu of snow depth data • Use SWE, Prec, Depth and Temp data together for more information. • Beware of sensor “flutter” • The good news is -99.9 probably means its snowing • SNOTEL wind data is not measuring ridge top wind There are no face-shots on the internet. Go ski!

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