Snowfall Measuring Procedures
Photo courtesy of Grant Goodge
Measuring snowfall accurately and precisely is important but surprisingly hard sometimes. We at the National Weather Service rely heavily on volunteers and the general public to provide snowfall measurements during winter weather events. We ask that you follow the procedures below as closely as possible when measuring snowfall and then forward the report on to us. Methods for forwarding those snowfall reports on to us will follow at the bottom of the page.
For the most accurate snowfall measurements, it is suggested that a snowboard be used. A piece of wood, painted white about 16" by 16" will work well. Other good alternatives include a spot on a wooden deck approximately 20 to 30 feet away from the house or a picnic table in an open, unobstructed part of the yard. It is not a good practice to measure the snow directly in the grass as the snow amount will be inflated by the blades of grass.
The snowboard is used to measure new snowfall and will need to be cleaned off after each measurement. To measure snow depth, you can place a second snowboard near the first one. This snowboard will not be cleaned off after each measurement and will allow for natural settling and melting to take place, allowing for a more representative measurement of snow depth. A ruler or yardstick can also be staked out in your yard to facilitate easy snow depth measuring.
Taking the Observation
Now that the snow has fallen, the following steps should be taken to get an accurate measurement. The two measurements that we need most from observers are new snowfall and total snow depth at time of observation.
Photo courtesy of Tony Edwards
New Snowfall: This is the amount of snow that has fallen since your last measurement, or since the first flakes began to fall. You don't want to include any snowfall left on the ground from a previous event with this measurement. The snow should be measured to the nearest tenth of an inch on the snowboard or other collecting surface. If there has been a lot of wind blowing and drifting the snow, it may be necessary to take more than one measurement on the snow board or collecting surface and average the measurements together to get a more representative total. Once you've recorded the new snowfall, clean off your snowboard or measuring surface.
Snow Depth: This is the amount of all snow on the ground and may include snowfall that has fallen in previous events. On your second snowboard, or on a flat piece of ground, measure the total snowfall to the nearest inch. Again, more than one measurement may be needed if there's been a lot of wind or some melting has taken place and the snow is not evenly distributed across your measuring surface. If more than one measurement is needed, average all the measurements and record the snow depth to the nearest inch.
Sending Your Report
Once you've measured the snowfall, we encourage you to send us your report. There are a couple of ways to do so:
- If you're one of our storm spotters, please give us a call on the 1-800 number provided to you during your training or send your report via e-Spotter.
- Otherwise, send us your report via Facebook or Twitter. Don't forget to include your location in your report.
That was just the basics. If you would like more information on how to accurately measure snowfall or information on the other types of useful snowfall and winter precipitation measurements, then please see the following resources:
The Snow Booklet: A Guide to the Science, Climatology, and Measurement of Snow in the United States