For decades, snowfall forecasts have typically involved the issuance of a range of accumulation amounts, typically (but not always) based on a factor of two. For example, 3-6 inches, 4-8 inches, etc.
I have no idea why. Perhaps it is a convenience thing. Maybe people like it that way. I don’t know what that range even means. Does it represent the middle 50% of possible outcomes, with a 25% chance of more and a 25% chance of less? Does it represent the middle 80%? Why always use a factor of two? Sometimes the range needs to be bigger, especially in longer range forecasts.
And then there is my favorite, “higher amounts in favored locations.” What the hell does that really mean and how do you verify it?
There was a time when snowfall forecasting was truly guesswork, but things are changing. Computer models are now capable or will soon be capable of simulating smaller storm details, what meteorologists call “cloud scale.” Ensembles can be used to better estimate the future outcomes. There remains much work to do, but there is great potential to dramatically improve snowfall forecasting.