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Post date: Apr 06, 2016 2:2:40 AM
There certainly was A LOT more snow on the ground this April 1 than last year's, however not as much as many hoped for. Across California the totals come to 95% in the north, 88% in the central, and 73% in the south for a state-wide total of 86% for 2016 (source). For Lassen Volcanic National Park, the amounts are much better at 122%. Yosemite is at the higher end at 91% and 89% for the Merced and Tuolumne drainages, respectively. Similar April 1 amounts for Yosemite occurred in 2009, 2004, 2002, 1989, and 1984 (see table below; source).
Based on these past years, the Glacier Point Road should open sometime in early- to mid-May while the Tioga Pass Road should open a little after mid-May. When I use the data from the nearest weather stations I get slightly different values. To the right is a graph of what 2016's snow accumulation looked like at Ostrander Lake (STR). I like looking at median (1989-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 101%. According to the median, it is 114%. The snow accumulation at Dana Meadows (DAN) is more similar to the overall Yosemite results with the snowpack at 93% of mean and 98% of median (1981-present). For the Glacier Point Road, STR (73% of variability) predicts an opening date of May 17 and DAN (57% of variability) predicts May 23. Based on previous years and the amount of variability accounted for, STR appears to be a better predictor. For the Tioga Pass Road, STR (74% of variability) predicts an opening date of May 28 and DAN (48% of variability) predicts May 23. STR shows better correlation but the DAN prediction correlates better with previous years with similar snowpack. Therefore, I'll use a mix of the two stations and previous years to make my predictions. I estimate that the Glacier Point Road will open sometime between May 9 and 17 and the Tioga Pass Road will open sometime between May 16 and 24; in time for Memorial Day weekend. Should these predictions prove accurate, the roads will open slightly earlier than an "average" year. Yosemite Valley waterfall volume should be peaking after mid-May and probably closer to the end of May. However, this will also depend on what the weather does from now until May. Check back in a couple of weeks when I update this post with April 15 numbers.
UPDATE (4/16):
Plowing is nearly complete on the Glacier Point Road, but currently there is no estimated opening date. Plowing on the Tioga Pass Road begins April 18. The snow around Yosemite has begun to melt from its peak depth between mid-March and early-April. With April 15 SWE values, STR (73% of variability) is a slightly better predictor for the Glacier Point Road than DAN and predicts an opening date of May 15. DAN (73% of variability) predicts May 16. However, since plowing is already almost complete, I believe these estimates are probably a little late. For the Tioga Pass Road, STR (78% of variability) is again better and predicts an opening date of May 24. DAN (59% of variability) agrees. Again, however, I believe these estimates to be on the late side. I'd like to move my Glacier Point Road estimate up based on the plowing update, but I already adjusted it for the April 1 estimates. Therefore, I'm only going to adjust the Glacier Point Road estimate slightly and keep the Tioga Pass Road estimate the same.
I estimate that the Glacier Point Road will open sometime between May 7 and 15 and the Tioga Pass Road will open sometime between May 16 and 24.
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