Weather Talk: Good snow measurement takes time
During last Saturday's heavy snowstorm, many people were complaining on social media about the absence of "official" Fargo-Moorhead snowfall updates during the storm. It wasn't negligence on the part of the media; there are rules about measuring snow.
It begins with a white board of specific dimensions that is kept clean in between measurements. As snow falls over a long period of time like last Saturday, the weight of the snow causes the crystals to break, allowing the snow to settle. If a snow observer were to measure the snow every hour, sweeping the board clean with each measure, the result would be ridiculously high. On the other hand, if the observer were to wait until after a long snowfall, wind and weight-settling would yield an amount too low.
The rule is to measure no more than four times in 24 hours with at least four hours between each measure. This process makes for the most accurate snowfall recordings, but it means sometimes waiting for results.