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No matter how hard it’s snowing, those flakes don’t count as “measurable” unless they pile up to at least 0.1 inch (0.25 centimeters) on the ground. Otherwise, they merely count as a “trace.” That’s one of the many little-known facets of snow measurement as practiced by the National Weather Service (NWS), along with thousands of U.S. volunteers. Another noteworthy fact: an inch of water can produce widely varying amounts of snow.
Find out what separates fluff from cement with the interactive graphic below.
For more on the challenges of measuring snow, see this feature story on How deep the snow? If you’ve got the urge to quantify and the taste for tromping in snow, consider volunteering as an observer with the NWS Cooperative Observer Program and/or CoCoRaHS (the Community Collaborative Rain, Hail and Snow Network).
Winter storms & snowpack (NCAR Research Applications Lab)
Student & teacher resources on snowstorms & more (Spark: UCAR Science Education)
Online training related to measuring snow (MetEd training from UCAR's COMET Program)
CoCoRaHS Snow Training Webinar (YouTube)
Click a button to see changes in accumulation