10 May Corn Skiing Season Is On!!
This is a summary of snow conditions, the overall avalanche situation and road access in the Eastern Sierra at the beginning of May 2023.
Winter is on the retreat in the Sierra. The massive amount of snow we received is giving way to spring at lower elevations. All of us who lived and shoveled our way through this winter can’t deny a huge sense of relief! However, there is still a lot of snow above 9000ft. and we will be able to ski well into June this year. To give you a picture of the snow cover and skiing quality I have compiled some observations from my recent travels in the mountains.
● In the southern part of the range, Bishop and south of it, the snow line is moving uphill fast and currently hovers around 8500ft. In gullies, you will often find arms of snow extending down farther than on ridges or moraines, which are exposed to more direct solar radiation and wind. Basin or Birch Mountain for example, have several arms of snow still extending down farther in shallow gullies.
● North of Bishop the snow line hovers around 7500ft. Depending on the aspect, the cover is becoming more shallow and is very susceptible to solar warming. A good example of this is the Convict Lake area. The east aspect of Mono Jim clearly displays the impact of the intense solar radiation and high temperatures creating a more shallow snow cover that is riddled by Glide Cracks. A D2 Wet Slab was triggered by a Loose Wet slough that skiers set off up higher on the steep east facing slope. Later, during the same warm spell, some Glide Cracks failed spontaneously in an adjacent gully and took out the whole season’s snowpack to the ground along with a lot of dirt and rocks.
● The recent warming spells have caused several shedding cycles. Many steep and tight couloirs are filled with avalanche debris and the skiing quality is becoming quite poor. The Mendenhall Couloir and the Mayfield Couloir are examples for this.
● Last week we experienced a cooling trend with increased cloud cover, moderate to strong winds and light snowfall. The cloud cover and winds were cooling the snow surface enough to slow down the corn cycle and even prevent the snow surface from softening altogether. The few inches of new snow accumulated provided some localized spring powder skiing, mostly found in the Mammoth Lakes Basin and north and above 10500ft. on northerly aspects. Localized deeper accumulations resulted in Wind Slabs that caught several backcountry skiers off guard. We saw a couple of D1 to D1.5 Dry Loose sloughs and a couple of skier triggered shallow Wind Slabs that ran on the firm old snow surface. (See ESAC observations for Ship’s Prow and Matterhorn Peak)
● Today we are swinging back into a sunny period with temperatures of 48°F at 10,000ft. Clear skies will allow for intense solar radiation and put us back into a spring diurnal warming cycle that causes avalanche instability to rise throughout the day. The skier triggered Loose Wet Slough that triggered the Wet Slab on Mono Jim was a good illustration of this pattern of avalanche instability. Your best defense on warm and sunny days is to get a very early start and ski down when the top two to three inches of the snow surface are soft. That’s where you will find the sweet spot for perfect corn skiing. The window for good corn skiing on warm and clear days with intense solar radiation is pretty short. Both in how much time you have to ski good corn and what elevation bands and aspects will ski well. The snow deteriorates very quickly and becomes sticky or heavy and rotten. Use elevation bands and aspects to your advantage. I recently skied out through Horse Creek Canyon from an overnight trip in the Sawtooth. It was an overcast day with light winds gusting to moderate. After an early morning mission up high we packed up camp and skied out at 10:30. At that time the snow had turned to a bottomless mess below 9500ft. on all aspects.
● Understanding and tailoring your trip to the sun and temperatures will be important. Look for a solid overnight freeze to help keep the snow firm longer. High elevation east aspects are getting the first sunlight of the day. On warm days expect those slopes to be ready to be skied as early as 8:00 or 8:30 am. On April 28th I saw a Loose Wet avalanche run at 9:30 am hiking up Horse Creek out of Twin Lakes. It ran on a steep, rocky East facing slope with shallow snow cover. The slide entrained a lot of dirt and rocks and ran at least 1000ft.
● Use your ski boot and step on the snow every hour or so to measure the boot pen. If your boot sinks in to the top of the boot or deeper, you have stayed out too late. Now you are dealing with a substantial amount of loose wet snow that could form powerful loose wet sloughs.
● SW to W and especially NW high elevation slopes receive a lot of strong solar radiation in the later part of the day until the sun sets.
● North aspects in shaded and steep locations, can still hold dry, wintery snow, especially after last week’s new snow and cold temperatures. Look for these conditions above 10,500ft in the Mammoth area and in the northern part of the range. I skied Ski Dreams on my recent Sawtooth trip and the N facing center of the feature was still holding firm but edgeable, wintery snow. Swinging slightly to a different aspect on either side of the slope, the snow surface was a firm and sun affected crust.
● There is a wide range of variable snow surface textures to be found. These range from smooth panels of snow on planar and open northerly slopes to large corn flake texture on features exposed to more wind and strong solar radiation. E aspects are often highly featured with 3D water runnels. It helps to scope out your descent line and the smoothest looking snow on your way up.
● On early morning approaches expect very firm snow surfaces. Ski crampons are essential. For steeper slopes you will need boot crampons and an ice axe. Slide-for-life conditions exist if the snow surface doesn’t soften on cloudy days with winds and cooler temperatures or if you are too early in the day. Catching a classic Sierra couloir on the right day and in the right conditions will be well worth the patience it takes to wait for the right conditions.
● Many Creeks are starting to open up and most lower elevation Lakes, like Convict Lake, Lundy or Twin Lakes are no longer frozen. Creeks are running fast and deep, especially after a warm, sunny day. Be heads-up with creek crossings. Using hiking poles can help you be more stable. And it’s always a good idea to open up the waist buckle and chest strap on your backpack for a river or log crossing. This will allow you to free yourself from the heavy pack in case of a slip and fall.
Check for road status and closures
● Mono County:
https://monocounty.ca.gov/roads/page/county-road-closures
● Inyo County:
https://www.inyocounty.us/sites/default/files/2023-04/CURRENT%20ROAD%20UPDATE
%204.25.23%20%20REV.%20A%20_0.pdf
Author: SMG Guide Barbara Wanner