* WHAT...Heavy lake effect snow. Additional snow accumulations 1 to 2 feet, locally up to 3 feet. Snowfall rates of 3-5 inches per hour possible in the most intense part of the band, lessening to 1-2 inches per hour overnight. * WHERE...Oswego and Lewis Counties. For Lewis County, additional snowfall will be confined to the southern portion of the county with much lower snowfall totals. * WHEN...Until 7 PM EST Saturday. * IMPACTS...Whiteout conditions are expected and will make travel treacherous and potentially life-threatening. Travel will be very difficult to impossible. The hazardous conditions will impact travel through the week.