Central Sierra Nevada
Avalanche danger
Highlights
While triggering an avalanche has become unlikely for today, it is not impossible especially in areas where firm wind slabs may linger. The avalanche danger will increase as more snow and wind impact the forecast area tonight. Widespread icy surfaces, variable snow conditions, and strong winds present additional hazards today including long sliding falls. LOW avalanche danger exists for all elevations. Travel using normal caution and be willing to step back into safer terrain if conditions warrant.
Avalanche Discussion
Triggering an avalanche has become unlikely on a regional scale for today. Some areas of drifted snow may form today, but these should remain small and shallow since the forecast only calls for up to 2 inches of new snow in some places. Unlikely does not mean impossible. Unstable snow could still lurk on some isolated slope in the forecast area especially high in the Mt. Rose backcountry where firm and hard to trigger wind slabs may exist. Wind slabs will come back as a problem tomorrow if the forecasted snow materializes tonight. If more snow falls today than the up to 2 inches forecasted, wind slabs could come back sooner.
While triggering an avalanche may be unlikely, variable snow conditions have made backcountry travel challenging. A high-elevation rain event combined with strong winds has left firm icy surfaces on many slopes. A fall on one of these could easily result in a long uncontrollable slide. In areas where the crust is thinner, breakable crust conditions exist. Wind-hammered, variable, uneven, and firm surfaces exist in the few places where the rain crust is absent. Strong winds will add to the challenge of over the snow travel today.
Today's travel plans should account for challenging snow conditions and strong winds. Monitoring the snow conditions and talking about them with your group can help avoid ending up in an area where conditions exceed your group's abilities or comfort levels. Even though the avalanche danger is LOW, stay alert, and don't ignore signs of instability or unforeseen changes in weather or snow conditions.
Recent Observations:
* Yesterday we found firm icy rain crusts on the exposed areas up to the summit of Mt. Lincoln and Mt. Judah (Donner Summit). In a few spots, some ribbons of windblown snow existed. Once we got into more sheltered areas a mix of breakable rain crust and dust on breakable rain crust existed.
* The rain crust has been reported all along the summits of the Sierra Crest and up to 10,800 ft on Freel Peak. Variable conditions ranging from firm and icy to breakable crusts to dust on breakable crust are widespread. The one exception so far is an observation from Tamarack Peak (Mt Rose backcountry) where a dense layer of supportable snow existed at or near the surface but the rain crust did not. Widespread wind effects existed in the Tamarack Peak area. Snow surfaces varied ranging from firm wind-buffed snow to breakable wind crusts to shallow soft snow on top of supportable snow in the most sheltered areas.