This is how I came up with the target date of 1-18,starting with monday 1-11,and ending with sunday 1-17,I added the daytime highs with the nightime lows,then divided by 2 for the avg. temp.Then added those temps. together,and divided by 7,and came up with 21 deg.Then applied that temp.to the ice growth chart.How will snowfall affect this theory,I dont know,but guessing it should be close to accurate,time will tell.