In the winter, many hope for a winter wonderland every time a storm approaches. Obviously, we don’t get snow every time a storm rolls through, but when we do, you may hear two terms: snowfall & snow depth.
Normally for Northwest Arkansas and the River valley, the two are synonymous, but what if we have a storm where we start with snow but end with sleet, freezing rain, or rain? What if we get multiple winter storms back to back? Now, you may have a difference in the two measurements.
Snowfall is used for a single snowstorm or length of time. For example, a daily or monthly snowfall total. When measuring snowfall, you need to do the following:
- You need a dry, flat surface away from any buildings, trees, or anything that could disturb the snow as it falls.
- If there is snow on the ground already, you need to know what the snow depth is already and subtract that original amount from the total.
Snow depth is exactly the way it sounds. It is the cumulative amount of snow currently on the ground.
It is possible to get a snowfall that is greater than the snow depth in a storm! If we get a storm that begins with snow and then changes to another form of precipitation (sleet, freezing rain, or rain), the observer needs to take the snowfall measurement at the start of the transition according the National Weather Service guidelines for snow measurement.
Since the precipitation could compress or melt some of the snow, your snow depth measurement could be less at the end of the storm. For example, if Fayetteville received 3.0″ of snow and then the snow transitions to rain, the snow depth may decrease to 2.5″. When the observer takes a weather observation after the storm, they would report a snowfall of 3″ with a current snow depth of 2.5″.
So if you want to make sure you get an accurate snowfall measurement in the next snow storm, remember these things:
- Make sure you have a wide, open space that will not be impacted by the wind moving around buildings, trees, and other obstructions. The NWS recommends at least a distance of twice the height of the tallest structure (if you have a 10-foot tree near by, you should measure at least 20-feet away).
- If the snow changes to another form of precipitation, be sure to grab the snow measurement at the start of the transition to avoid compaction.
Learn more about the NWS’s snow measurement guidelines here: shorturl.at/rzPW2. While the Gaylord NWS office is located in northern Michigan, the guidelines are the same across the country.
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