This is the last Snowpack Summary for the 2017/18 season but there’s still plenty of snow in the higher elevations for the motivated skier. As the season moves deeper into Spring, keep in mind that the danger of Loose Wet avalanches will likely linger through May in the mid to upper elevations, especially on steep solar aspects and in rocky terrain. Generally, they’ll be relatively small (D1 most likely, natural and triggered) with a few D2 possible in isolated locations. Larger (D3) releases may be possible in favored locations but will likely require a large trigger (cornice fall, etc.) or heavy rain. The best way to limit the threat of Loose Wet avalanches is to plan your travels around early AM starts and completing your travels before mid-day. N-NE aspects will be slower to transition fully to corn snow and will likely lag behind the rest of the aspects in terms of improving stability until they have had an opportunity to cycle through a few good freeze thaw cycles.
Spring can bring fast moving storms that are accompanied by quick hit of new snow and strong winds, which can quickly form Wind Slabs on top of the firm spring snow. The firm corn snow can act as a good bed surface for Wind Slabs to slide on but they generally strengthen and bond fairly quickly. Use additional caution if going out into the backcountry during a strom or immediately after it clears.
Keep in mind the different hazards that spring skiing brings such as: Slide For Life conditions, rock fall, hazardous creek crossing, cornice fall or collapse, and occasional lightening.
Firm snow conditions are a major hazard should a fall occur in steep or complex terrain. Plan accordingly to either avoid these slopes until they begin to thaw or carry ski and/or boot crampons, ice axe, and a helmet are recommended. These tools can reduce the risk and consequences of a fall but you need to learn how to use them safely and practice self-arrest regularly to maintain proficiency.
Cornices – slopes with overhanging cornices should be avoided or approached with extreme caution. This is the time of year where they begin to sag and collapse without warning, and triggering an avalanche on the slope below. Also, be cautious while traveling along corniced ridgelines where cornices may fail without warning and often break much further back from the edge than anticipated.
Rock fall – can occur anytime but often picks up as the sun begins to heat rocky faces or as water begins to freeze in the cracks. Keep in mind couloirs are great way to ascend but they act as garbage chutes for rocks and potential cornice falls. A helmet can protect you from small rocks but timing and good route planning is your best defense.
Thunder Storms – not a frequent visitor to the eastern Sierra but not uncommon this time of year when the upper atmosphere is unstable. The weather service is quite good at identifying the conditions for thunderstorm development. Check the forecast to determine the likelihood prior to embarking for the backcountry. Generally, they begin to form over the high country mid-morning and become fully developed by mid afternoon. Plan to be out of the mountains early if thunderstorms are forecasted.
Creek crossings – most snow bridges have collapsed at this point or are on the verge. This may mean crossing creeks with fast moving water. Do not underestimate the power of swift water. Water approaching knee height is borderline for crossing without the aid of poles or partners. Beware of what’s down stream before any crossing. Avoid crossing with sweepers, dead snags in the water, or rapids down stream. Hypothermia is a real concern during the spring if a person becomes immersed for any length of time.
