Avalanche forecast

Central Sierra Nevada

Issued Apr 11, 2018valid to Apr 12, 2018Sierra Avalanche Center

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Avalanche danger

Alpine

3 · Considerable

Treeline

3 · Considerable

Below

2 · Moderate

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Out of date — this forecast expired 8 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The avalanche danger may rise to MODERATE during the day if enough warming occurs for loose wet avalanches to become possible. Once the storm arrives over the forecast area this evening the avalanche danger will quickly rise to CONSIDERABLE during the night due to newly formed wind slabs and storm slabs. Slab avalanche activity will be an issue tonight and slab instabilities will linger into tomorrow.

Avalanche problems

Loose Wet
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Possible
Size
1
Some refreeze should have occurred last night due to temperatures near freezing but partly cloudy skies may have kept the snowpack from experiencing a strong overnight refreeze. Enough warming may occur on some slopes today for loose wet instabilities to become possible on any aspect if slopes get enough sun exposure. If cloud cover becomes more widespread, it may limit the amount of warming that happens today. If loose wet instabilities do form today, they could manifest as roller balls, pinwheels, or loose wet avalanches. If the surface refreeze does melt today, deep wet snow exists below it and larger loose wet instabilities could occur.

Step off your equipment regularly to test how supportable the refreeze is. Once you start stepping into deep wet snow it is time to call it a day.
Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Likely
Size
2
New wind slabs will form on leeward aspects tonight as new snow and strong winds impact the forecast area. These wind slabs will likely form faster than they can bond to the existing snow and wind slab avalanches will become a problem during the night. Some natural wind slab avalanches may become possible and if a person happens to be traveling in the backcountry tonight, expect human triggered wind slabs to become likely. Wind slabs will form on wind-loaded N-NE-E aspects and cross-loaded NW and SE aspects in near and above treeline terrain. Depending on the amount of snow that accumulates, some wind slabs could grow large enough to bury or injure a person or maybe even a car by tomorrow morning in heavily wind-loaded areas. Wind slab instability will likely linger into tomorrow.
Loose Dry
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Possible
Size
1
Storm slabs may also become a problem tonight during the storm. Changing conditions and periods of rapid snow accumulation tonight may create and overload weaknesses that form during the storm. Human triggered storm slab avalanches may become possible tonight on steep slopes loaded with new snow. Some of these could grow large enough to bury or injure a person after midnight.