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The following procedures were developed from previous National Weather Service procedures and input from a broad array of expertise from climatologists, snow specialists, weather observers, and data users. Some of the materials have been extracted from "The Snow Booklet" by Nolan J. Doesken and Arthur Judson, CSU, 1996).
It is essential for all observers to understand the importance of taking standard measurements in the prescribed consistent manner. Inconsistent observing and reporting methods result in incompatible data which can result in profoundly incorrect differences between stations and observers.
Each season before the first snows come: Review these instructions for measuring snow. It is sometimes easy to forget what needs to be measured.
At the beginning of each snowfall/freezing season, remove the funnel and inner measuring tube of the eight-inch manual rain gauge to expose the 8-inch diameter overflow can so that it can more accurately catch frozen precipitation.
Put your snowboard(s) out and mark their location with a flag or some other indicator so they can be found after a new snowfall. They should be located in the vicinity of your station in an open location (not under trees, obstructions, or on the north side of structures in the shadows).
Check your gauge to make sure there are no leaks. If there are leaks, take appropriate action.
Once your equipment has been readied for winter, you are prepared for taking snowfall measurements.
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Observers should determine three values when reporting solid precipitation. They are:
Measure and record the snowfall ( snow, ice pellets) since the previous snowfall observation.
Determine the depth of snow on the ground at the normal observation time,
Measure and record the water equivalent of snowfall since the previous day's observation.
Measure and record the greatest amount of snowfall that has accumulated on your snowboard (wooden deck or ground if board is not avail
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able) since the previous snowfall observation.
This measurement should be taken minimally once-a-day (but can be taken up to four times a day, see note on the next page) and should reflect the greatest accumulation of new snow observed (in inches and tenths, for example, 3.9 inches) since
the last snowfall observation. If you are not available to watch snow accumulation at all times of the day and night, use your best estimate, based on a measurement of snowfall at the scheduled time of observation along with knowledge of what took place during the past 24 hours. If you are not present to witness the greatest snow accumulation, input may be obtained from other people who were near the station during the snow event. If your observation is not based on a measurement, record in your remarks that the "snow amount based on estimate".
Remember, you want to report the greatest accumulation since the last observation. If snowfall occurred several times during the period, and each snowfall melted either completely or in part before the next snowfall, record the total of the greatest snowdepths of each event and enter in your remarks "snowfall melted during the OBS period". For example, three separate snow squalls affect your station during your 24-hour reporting day, say 3.0, 2.2, and 1.5 inches. The snow from each event melts off before the next accumulation and no snow is on the ground at your scheduled time of observation. The total snowfall for that reporting 24-hour day is the sum of the three separate snow squalls, 6.7 inches, even though the snow depth on your board at observation time was zero. Snow often melts as it lands. If snow continually melts as it lands, and the accumulation never reaches 0.1 inches on your measuring surface, snowfall should be recorded as a trace (T) and record in your remarks that the "snow melted as it landed".
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