Measuring snow and ice can be tricky, especially if it is windy. However, with some background information and understanding, severe weather spotters can do a good job of measuring snow and ice.
Basically, as a minimum, the National Weather Service (NWS) measures snow and ice once every 6 hours. Some co-op observers measure snow once per day, usually sometime around 6 or 7 am local time. The NWS then adds up the snow that fell in each 6-hour period to arrive at the total 24-hour snowfall for a calendar day, or from 6 am to 6am. At the end of each 6-hour period the NWS then brushes the snow off the 6-hour snow board. In order for snow measurements to be considered for the record books, the NWS can't use time periods less than 6 hours.
Granted, one can measure snow accumulations on an hourly basis, but for the official record books, we measure once every 6-hours on the 6-hour snow board. Since snow settles as air is squeezed out due to the weight of new snow on top, the total of the hourly snow measurements during a 6-hour period will usually be greater that the "once per 6-hour" snow measurement. However, we do not add up the hourly snow measurements during a 6-hour period to arrive at the 6-hour snow accumulation - we measure only once every 6-hours on the 6-hour snow board to arrive at the 6-hour snow accumulation.
Ice and sleet accumulations are also measured on a 6-hour basis, and we measure the thickness of the ice on exposed surfaces and the depth of the sleet, both in tenths of an inch.
Here's an example:
12 am to 6 am......4.2 inches of snow. 6am to 12 pm.....3.8 inches 12 pm to 6 pm.....2.5 inches 6 pm to 12 am.....5.4 inches.
Total snowfall for the calendar day equals 15.9 inches.
Here are some links that give you more background information on how to measure snow:
If you have any questions about how to measure snow, please contact Rudy Schaar, our Data Acquisition Program Manager at:
Thanks for your interest in providing snow measurements to the NWS!
...Rusty Kapela, WCM