I tend to check sites like weather.com, weatherbug.com etc and look at what they project the winds to be throughout the day. If it's out of the South less than 10mph, the lake should be flat as glass. If they show out of the south less than 10, building 10-20mph, then it should be nice in 100fow or less and really rough out deep. If it's N, NW, W greater than 10mph, it's going to be bumpy! But make sure to check the hour by hour detail, as it may be calm in the morning and rough later or vice versa. The wave forecasts say what it will be like at some point during the day and often are right for about 5 mins
Nick