Every year the opening of Highway 20 through the North Cascades National Park heralds a phase transition in the population density of the Methow Valley. From our home in Seattle to Winthrop this is the difference between 247 miles and 202 miles. For beautiful pictures of this years plowing of the road, see the WSDOT’s flickr page. Since the opening of the pass brings business, and busyness, locales like to try to predict the date it will open. So when will it open this year?
Here is a plot of the day of the year the road opened, and snow depth at the Swamp Creek snotel station on 3/1 of that year:
I’ve also calculated a least squares fit and plotted value of this fit for the given snow depth. Using this fit, and the fact that on 3/1 of this year there was 73 inches of snow, I can therefore predict, with absolute certainty (ha!) that Highway 20 will open on day 132 of this year, or May 12. A very late opening.