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National Weather Service Portland-Gray Maine



Find a location where the snow appears to be near its average depth. Avoid drifts or valleys. Look for a flat, somewhat open area away from buildings and trees. Some trees in the distance may be helpful in making a wind break, preventing drifting, and thus providing for a more even distribution of the snow. Measure the depth with the snow measuring stick (aka "the common household ruler") at several locations and use an average. Traditionally ten measurements are made and the average value is the snow depth. When snow has fallen between observation times and has been melting, measure its greatest depth on the ground while it is snowing, or estimate the greatest depth. During heavy snowfall some of the actual total may be lost due to compaction of the column by the weight of the snow, during these times it may be best to estimate a slightly higher value if snow has been falling at a heavy rate for several hours since the last actual measurement. If all snow melted as it fell, you can estimate a total if you think more than a half of inch fell before melting, or report a trace for the snowfall.


When fresh snow has fallen on old snow, it is necessary to measure the depth of the new snow (in tenths of inches) and the total snowdepth (whole inches). Snow boards provide the best method of taking measurements in this case. Sometimes if the old snow has settled or partially melted enough to develop a crust or to be noticeably denser than the new snow, it may be possible to insert the snow stick until it meets the greater resistance of the crust of old snow, and to use this depth as the amount of new snow having fallen.

Use of a Snow Board

Snow boards are laid on top of the old snow when there is any possibility of new snow falling. Push them into the snow just far enough that the top of the board is nearly level or just above the top of the old snow. After each observation, boards should be cleaned and placed in a new location. Because of evaporation or drifting, they may need adjusting daily to assure that the top of the board remains flush with the old snow. A clean sidewalk or open cement area where there is some protection from the wind and drifting is a good alternative to using a snow board. You still need to clean an area off before the snow starts and between measurements in order to accurately measure the newly fallen snow.

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Page last modified: December 10, 2002
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