Glacier Point and Tioga Pass Roads Opening Dates 2017
Post date: Apr 08, 2017 4:11:48 AM
Drought buster. The winter we thought would come last year came in 2017 instead. Three quarters of CA are no longer classified as experiencing drought conditions (source) and nowhere is it 'extreme' or 'exceptional'. Across California the snow totals come to 148% in the north, 173% in the central, and 163% in the south for a state-wide total of 163% for 2017 (source). For Lassen Volcanic National Park, the amounts are similar at 172%. Yosemite is also similar at 168% and 177% for the Merced and Tuolumne drainages, respectively. However, new records were set at Tioga Pass (213%) and Vogelsang (217%). Similar April 1 amounts for Yosemite occurred in 2011, 2005, 1998, 1995, 1993, and 1983 (see table below; source).
Based on these past years, the Glacier Point Road should open sometime in late-May to early-June while the Tioga Pass Road should open between mid- to late-June. When I use the data from the nearest weather stations I get slightly different values. To the right is a graph of what 2017's snow accumulation looks like at Tenaya Lake (TNY). Again, I like looking at median (1999-present) values to compare what "average" looks like because the actual average or "mean" gets skewed by extreme values at the end of the season. The median represents a more realistic curve. According to the mean, this year's April 1 snowpack is at 235%. According to the median, it is 244%. The snow accumulation at Dana Meadows (DAN) is more similar to the overall Yosemite results with the snowpack at 171% of mean and 182% of median (1981-present). Tuolumne Meadows (TUM) snow accumulation is similar to that of TNY at 223% of mean and 250% of median (1980-present). Unfortunately, the sensor at Ostrander Lake (STR), the best predictor of opening dates, gave out in January. For the Glacier Point Road, TUM (59% of variability) predicts an opening date of July 1 and DAN (53% of variability) predicts June 16. Based on previous years, DAN appears to be a better predictor but both seem late. For the Tioga Pass Road, TNY (68% of variability) predicts an opening date of July 5 and DAN (48% of variability) predicts June 12. TNY shows better correlation but the DAN prediction correlates better with previous years with similar snowpack. Therefore, I'll use a mix of all of the stations and previous years to make my predictions. I estimate that the Glacier Point Road will open sometime between May 26 and June 3 and the Tioga Pass Road will open sometime between June 16 and 24. Should these predictions prove accurate, the roads will open somewhat later than an "average" year. Glacier Point Road may be open for Memorial Day weekend (logical target for the park) but the Tioga Pass Road is not likely to be. Yosemite Valley waterfall volume should be peaking around mid- to late-June. However, this will also depend on what the weather does from now until then. Check back in a couple of weeks when I update this post with April 15 numbers.
UPDATE (4/18):
The snowpack is continuing to accumulate, which is going to further push the opening dates back. Amazingly, a single lane has already been plowed to Glacier Point despite around 8 feet of snow there. Plowing on the Tioga Pass Road has not yet begun but crews are 'mobilizing'. The snowpack data is suggesting an even later opening date for the Glacier Point and Tioga Pass roads, but with a single lane already plowed to Glacier Point I'm hesitant to push the predictions back. This year's April 15 snow values suggest an opening date between early- and mid-June for the Glacier Point Road and late-June to early-July for the Tioga Pass Road. However, I'm tentatively going to keep my prediction for the Glacier Point Road but push the Tioga Pass Road opening back slightly. I estimate that the Glacier Point Road will open sometime between May 26 and June 3 and the Tioga Pass Road will open sometime between June 19 and 27.
