The measurement of rainfall is fairly straightforward, but snowfall presents problems that make measurements somewhat arbitrary.
For rain, the meteorology department at Pennsylvania State uses a simple cylindrical tube to catch it.
The amount that falls in a given period is poured into a smaller cylindrical tube that is carefully gradated and measured with something like a dipstick.
Many things can affect the depth of snow, especially wind and how frequently it is measured, both during and after a storm.
Because the weight of the falling snow packs down what is underneath, it might compact from 10 inches to 8 inches as air holes fill in.
The National Weather Service guidelines call for using a snowboard, a board exposed to catch snow, with the accumulation measured every hour through the storm and then brushed off, a time-consuming method.
Meteorologists at Penn State seek an average reading from ten different points after the snow stops.