How this map was made:

Since exact dates, rather than months, delimit the snow accumulation season, the technique to generate these statistics incorporated whole month and partial-month snowfall totals. Whole month snowfall totals (Dec., Jan., Feb.) could be used for all stations, however a weighted fraction of the monthly snowfall was used when the onset and/or end date fell within a month. This fraction was based on the number of days in a particular month that was included in the snow accumulation season. Therefore, since the snow accumulation season is variable throughout the state, snowfall totals must be compiled from unequal time periods for each station.

For each season, one gridded map was generated based on the individual station observations using a kriging technique. From this, a software procedure extracted the 25th percentile snowfall statistic for each gridpoint, based on the entire distribution for the given number of seasons. The units represent an annual snowfall total (inches) in which 25% of the observation are below the given value.