Many of us look forward to the first snowfall of winter and are eager to see our area’s totals tallied. However, measuring snowfall isn’t as simple as sticking a ruler into the snow and getting a number. Observers who report snowfall to the NWS follow strict guidelines for consistent and accurate measurements.
The main tool an observer needs is a snow board, also known as a “ruler stick.” The snow board is a square piece of plywood 16 inches on each side, painted white to prevent it from absorbing solar heat and melting the snow. The board should be set in an open area away from buildings, trees and fences.
Ideally, the snow board should be placed at a distance twice as far from any obstruction as it is tall. This ensures that the greatest amount of snow can be measured. Measurements should be taken at least once per day (no more than four times a day) as soon as the snow begins to fall, and at a time of the day that minimizes the impact of settling and drifting.
Observers will use the board to determine snowfall, which is reported as inches and tenths (for example, 3") or, in metric, grams (for example, 10.9 cm). It is also possible for a wintry mix event to occur wherein snow changes to rain. In these cases, the highest amount of snow recorded prior to the transition is reported. Any snow accumulations of less than a tenth of an inch are reported as traces.