Snow Today updates daily images on snow conditions and relevant data, and also provides monthly scientific analyses from January to May, or more frequently as conditions warrant.

About Snow Today

Goals & audience

Snow Today, a scientific analysis website, provides a snapshot and interpretation of snow conditions in near-real time across the Western United States, told with a unique combination of satellite data and surface observations. Whether you are part of the Earth Science community, a natural resources manager, or just someone wondering how much snow that last storm dropped in your neck of the woods or in your favorite mountains, this website speaks to you. Snow Today examines where snow is present, where it has snowed recently, and how much water is in the snow, while also comparing between snow today, snow yesterday, snow last year, and snow over the last few decades.

How do we do this?

Snow Today relies on satellite data collected hundreds of miles above Earth and data from snow monitoring stations in remote mountain areas. To map snow cover, our team takes daily satellite data and applies physically-based techniques, which have been refined to produce accurate snow cover maps and to map snow hidden from satellites, such as beneath clouds and forest canopies. While the satellite data show snow location, it does not provide direct information on snow depth or snow water equivalent (SWE), which is a measure of how much water is stored within snow. To complement the snow cover data, our team also analyzes SWE measured at hundreds of snow monitoring stations, many of which have records dating back to the 1980s. Snow Today uses SWE data to determine changes in snow quantity from new snowstorms that add water and from snowmelt events that drain melted snow from the snowpack. For stations with multiple decades of SWE data, Snow Today also compares recent SWE and snowstorm events to average conditions for that time of year. 

Resources

Moderate Resolution Imaging Spectroradiometer (MODIS) data: The MODIS Snow Covered Area and Grain-size (MODSCAG) data are provided by Snow Data System (SnowDS) at the Jet Propulsion Laboratory (JPL). The reflectance data are from NASA MODIS.

Snow station data: Snow station data are sourced from the Snow Telemetry (SNOTEL) network by the Natural Resources Conservation Service (NRCS), United States Department of Agriculture (USDA) and the California Department of Water Resources. The data are publicly accessed at www.wcc.nrcs.usda.gov/snow.

Computing: This work utilizes resources from the University of Colorado Boulder Research Computing Group, which is supported by the National Science Foundation (awards ACI-1532235 and ACI-1532236), the University of Colorado Boulder, and Colorado State University.

Acknowledgements

The Snow Today website is a collaborative effort of many team members at several institutions at the University of Colorado Boulder, including the Institute of Arctic and Alpine Research (INSTAAR), the National Snow and Ice Data Center (NSIDC), and the Cooperative Institute for Research in Environmental Sciences (CIRES). These analyses build upon the legacy of a similar website formerly maintained at NSIDC by the late Drew Slater. 

We would like to specifically acknowledge contributions from the following: Karl Rittger, Mark Raleigh, Mary Jo Brodzik, Mark Serreze, Agnieszka Gautier, Suzanne Craig, Daniel Crumley, Audrey Payne, Lisa Booker, Ted Scambos, Jeff Deems, Andrew Barrett, Donna Scott, Doug Young, Chris Torrence, Kate Heightley, Joni Reeves, and Jennifer Walton.

References

Rittger, K., M. S. Raleigh, J. Dozier, A. F. Hill, J. A. Lutz, and T. H. Painter. 2019. Canopy Adjustment and Improved Cloud Detection for Remotely Sensed Snow Cover Mapping. Water Resources Research 24 August 2019. doi:10.1029/2019WR024914.

Raleigh, M. S., K. Rittger, C. E. Moore, B. Henn, J. A. Lutz, and J. D. Lundquist. 2013. Ground-based testing of MODIS fractional snow cover in subalpine meadows and forests of the Sierra Nevada. Remote Sensing of Environment 128: 44–57. doi:10.1016/j.rse.2012.09.016.

Painter, T. H., K. Rittger, C. McKenzie, P. Slaughter, R. E. Davis, and J. Dozier. 2009. Retrieval of subpixel snow covered area, grain size, and albedo from MODIS. Remote Sensing of Environment 113(4): 868–879. doi.org:10.1016/j.rse.2009.01.001.

Dozier, J., T. H. Painter, K. Rittger, and J. Frew. 2008. Time–space continuity of daily maps of fractional snow cover and albedo from MODIS. Advances in Water Resources 31(11): 1515–1526. doi:10.1016/j.advwatres.2008.08.011.