Measured precipitation

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In order to compute the accumulation of the snow cover with reasonable accuracy, unbiased estimates of both the form and amount of precipitation are needed.

The precipitation data, used as input to the snow model, are based on point measurements of precipitation from one or more gages.
The catch of a precipitation gage can be deficient by a considerable amount during snowfall periods, especially if the gage is not shielded or if the gage is exposed to high winds.
Thus, it is likely that the precipitation input data are biased estimates of the true precipitation during periods of snowfall.
The snow model uses a mean gage catch correction factor to remove this bias.
This snowfall correction factor is a model parameter referred to as SCF.
Precipitation which is classified as snow is adjusted by SCF and added to the existing snow cover.
Rain which falls on bare ground immediately enters the soil-moisture accounting model.
Rain falling on the snow cover is added to the computed surface melt water.