Getting accurate snow measurements no simple chore

January is normally the snowiest month of the year. After a December that went down in the record books as the fourth snowiest, it looks like we’re getting a running start to posting exceptional totals for January as well. As of Jan. 9, Coeur d’ Alene had received a seasonal total of 72.8 inches of snow, with nearly a foot coming from the storm last Tuesday and Wednesday. Normal snowfall for the month of January is 21.2 inches, which we should easily exceed before the first half of the month is over.

Much media hype is based on snowfall measurements, and National Weather Service forecasters like to get as many measurements as possible in order to verify that particular snow advisories or winter storm warnings panned out as forecasts. Getting accurate snowfall measurements is not as simple as it may sound, though. There is more to it than just sticking a ruler out on your back porch. Wind, water content of the snow, and the location where snowfall measurements are taken (i.e., on your back porch, up against a fence, on the grass, or on asphalt) can greatly impact the number of inches you will end up with. How do you know if you have taken an accurate measurement?

Official snowfall measurements are taken on what is called a snowboard. Ideally, it is a 16-by-16-inch piece of wood, painted white, that is located away from any buildings in an unobstructed area. The board is wiped off after each measurement. It is painted white, because darker colors will absorb more heat, potentially contributing to melting of some snow as it collects. The size, allows one to take multiple measurements, in situations where the snowfall may not be uniform (i.e. due to windy conditions). If you want to get accurate measurements where you live, and don’t have a snowboard, a wooden deck or picnic table located away from the house, or really any flat, bare, surface will do. It is best not to measure snow in the grass, as the snow amount will be inflated by the blades of grass.

Several factors can make it difficult to get an accurate snowfall measurement. Melting is one problem, compaction is another if the snow is particularly wet and coming down hard. In my opinion, however, the most difficult situation occurs when the snow is very powdery and there have also been strong winds. During many such events, my backyard will have patches of bare grass, alongside drifts of snow several inches deep. The best solution to the latter problem is to take as many as 10 measurements in different locations and take the average.

In addition to the official procedure for measuring snow, there are also procedures for coming up with the total liquid equivalent. Liquid equivalent is just the amount of water you would have if all the snow melted. If you have a weather station, or just like to keep a running tally of your annual precipitation, you will have to melt all frozen precipitation to get its liquid equivalent. Those in the Cooperative Observer Program who report to the National Weather Service use a special type of rain gauge to collect snow and later determine the liquid equivalent. Snow collects in a large 8-inch cylinder which also has a smaller inner cylinder which measures only rainfall. Observers must take the gauge inside, pour a measured amount of warm water into the snow to melt it, pour the liquid into the inner cylinder, then measure the total of amount of liquid – minus the water added – to get the liquid equivalent of the snowfall.

Who ever thought weather observing could be such hard work?