Mammoth Basin Snowpack Summary - 2015-05-03 08:06

Avalanche Advisory published on May 3, 2015 @ 8:06 pm
Issued by Sue Burak - Inyo National Forest
Snowpack Discussion

Season Summary

The ongoing western U.S.. drought (2012-2015) presents a fine example of how variable the climate in this region of the world can be when compared with average or above average winters. Prolonged dry periods are not abnormal on geologic timescales and may be the rule rather than the exception, contrary to what we would prefer. The days of skiing  the many classic ski descents in the southern Sierra from summit to sagebrush may not happen very often.  

We have gotten a taste of what is possible in terms of dry winters. Most likely, a decent or even great snow year will occur in the next few years but there are no guarantees. In the nine years of  avalanche center operations, 4 winters were above average (2006, 2009, 2010,2011),  5 have been dry to very dry (2007, 2012, 2013, 2014, 2015) and one (2008) was just below average.  If climate scientists are right, the trend is for less snow to fall above 8,000 ft. with warmer storms and warmer winters.

Back to back dry winters have created a lot of consternation and many skiers and riders have  modified their recreational activities in response to low snow conditions. Perceptions of what most folks once considered a day of good skiing has evolved over the last several winters as we adapt to shallow snow coverage and the ever present threat of hitting rocks. Phrases such as “back when it used to snow” are more common in every day conversations.

Back in December, I had no idea the winter would be drier than last winter- surely we had hit bottom in 2014! But nature slapped us in the face again- this winter, 21 storms accounted for the season snowfall of 125 inches at the ski patrol study plot on Mammoth Mountain. In 1987, 195 inches was recorded at the study plot and 1987 was the driest year of the 7 year drought. The long term average snowfall from the winter of 1983 to 2015 is 357 inches, so this winter’s snowfall was 35% of the long term average.

The winter began with promise with 48 inches of snow and 6 inches of water content falling in December. We enjoyed the first turns of the season in TJ Bowl. Slope cuts produced small wind slab avalanches on wind loaded slopes. Of course there were a lot of rocks, but I thought surely the next couple of December storms would erase all signs of rocks.  









First ECT of the winter December 18, 2014. Hopes were high for a snowy winter.

January storms were moisture starved and only three storms reached the area; only 2.5 inches of snow fell in January in three storms! Psyche for skiing and riding began to wane as each forecasted storm never delivered the amount of snow promised. Nature’s New Year’s gift was a strong north wind event that created 2 to 3 foot high sastrugi on the San Joaquin Ridge. After the first week of January, temperatures reached the upper 50’s above 9,000 ft. What happened to our winter?

San Joaquin Ridge in mid-January 2015. Acres of sastrugi formed from relentless north winds.

In early February, weather forecasters identified an atmospheric river event that would bring heavy snow to the area. The storm brought the tropics instead of winter and more precipitation in the form of rain than snow. A rain/snow mix reached the 11,000 ft. summit of Mammoth Mountain. Icy glazed surfaces were everywhere- all aspects and elevations.

The rain and snow mix created a thick hard, impenetrable layer that became the prominent feature of the snowpack.  Digging snow pits became tedious and time consuming because the hard layer had to be cut into 12 inches squares before a shovel could get through. I posted many boring snowpit pictures of facet/crust combinations in February and March that looked the same no matter where the pit was dug.

Not everything was bad about the layer- new cold dry storm snow that fell at the end of February bonded well to the layer resulting in great skiing and mostly stable snow conditions in the Negatives and the Mammoth Crest into the first week of March.

Warm weather returned after the first week of March and cycles of crust/facet sandwiches created lousy snow conditions by mid-March though steep sheltered north facing slopes held settled powder, also known as near surface facets. Only three storms reached the area in March, dropping a depressing 7 inches of snow in a month that usually delivers many feet of snowfall.

The biggest storm of the season occurred in the first part of April when 21 inches fell in two days. We enjoyed great conditions on Mammoth Mountain and in the Mammoth Basin. It would have been nice if storms like this one occurred earlier and more often this winter, but unfortunately, winters that start in April might be the new norm.

One final April storm last week (April 25) dropped 8 to 12 inches in the Mammoth Basin. After a few days of widespread loose wet slides in north facing alpine terrain, good spring conditions can be reached after a short hike. Even in the driest winter since the 1930’s, there was enough snow that accumulated on north facing slopes in the Mammoth Basins to provide spring skiing in early May.

I know we are all hoping that next year will be memorable for heavy snowfalls and deep snowpacks. Thanks to all of you for reading the summaries this winter.










This snowpack summary applies only to backcountry areas outside established ski area boundaries. This snowpack summary only describes general avalanche conditions and local variations always occur. This snowpack summary expires 24 hours after the posted time unless otherwise noted. The information in this snowpack summary is provided by the USDA Forest Service who is solely responsible for its content.

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