Spring is back, the snow is melting, and I’m thinking of the mountains waking up after a long cold winter. The April 1st snowpack at Tuolumne Meadows was pretty close to average for the second year in a row. The winter rangers measured 19.5 inches of snow-water-equivalent at the Tuolumne snow course at the end of March. So, once again I’ll use the past measurements of April 1st snowpack and the corresponding year’s Tioga Pass Road opening date to try and predict this year’s road opening based on current snowpack. This simple model predicts the road should open on May 23rd this year, with a 50% chance that the actual opening date will fall between May 17th and May 29th.
Looking back at how well this model has performed over the past 7 years is indicative of how a single measurement of snowpack doesn’t capture all the factors that go into the complex operation of clearing a high mountain road for public access. The closest I’ve been was 6 days off in 2018, my first prediction year. The furthest off was during the first wave of covid in 2020 when I missed by 37 days. Last year was second worst, off by 19 days.
Interestingly, in each of the past 7 years the actual opening day has been later than I’ve predicted, never earlier. This could just be chance, or it could indicate that plowing and prepping the road takes longer now than it did in the past, for reasons unrelated to the amount of snow. Excluding 2020, the Tioga Road has opened an average of 13 days later than my prediction.
So let’s just add that correction to the snow-only model prediction of May 23rd and guess that the road will actually open on June 4th, with a 50% interval from May 29th to June 10th.

*Note that the model changes every year to incorporate the newest data, so the current graph does not match up with previous years’ predictions. This is most apparent for 2023. Before that data point was established, the right side of the graph was empty. Now that we have some data there, the model can match it better.
Find raw data here: https://www.nps.gov/yose/planyourvisit/seasonal.htm and here: https://cdec.water.ca.gov/reportapp/javareports?name=COURSES