Eastern Sierra Avalanche Advisory - 1/13/18

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THIS AVALANCHE ADVISORY EXPIRED ON January 14, 2018 @ 6:35 am
Avalanche Advisory published on January 13, 2018 @ 6:35 am
Issued by Doug Lewis - Eastern Sierra Avalanche Center

The primary avalanche concern for Saturday (1/13) continues to focus on the threat of Persistent Slabs where recent Wind Slabs and recent snowfall rests on foundation of weak faceted sugar snow. Triggered avalanches will remain possible today, especially on northerly aspects near and above treeline where the snow remains and cold are the areas of greatest concern.  

Below ~9,000’, natural and triggered releases are unlikely due to thin snow coverage (below threshold).​

 

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Persistent Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The primary concern during the forecast period remains the persistent slab problem created by the recent Wind Slabs (1/10) and snowfall (1/9) resting on a foundation of faceted sugar snow. Stability tests continue to show the potential for failure as well as reports of Whumphing on northerly aspects in the mid elevations. If a failure occurs, it has the potential to propagate across the slope and possibly eroding or step down into the snowpack. Sudden collapsing (Whumphing) is strong sign of instability and best not ignored. You will be most likely encounter this problem near, and above treeline on northerly aspects, especially on recently wind loaded slopes.

Below ~9,000’- below threshold, natural and triggered releases are unlikely due to low snow coverage.​ 

 

advisory discussion

The snowfall we received on 1/9 was a nice respite from the dry and dusty conditions that has dominated the recent weather across the west. Post storm winds increased Wednesday (1/10) forming stubborn Wind Slabs throughout the eastern Sierra, resulting in a small skier triggered release reported on the 11th near Crystal Lake and numerous naturals along the Crest and Virginia Lakes. Thursday, light snow showers moved into the region briefly along with moderate to strong Southwest winds leaving a dusting of snow in middle and upper elevations and a thin wind crust in its wake. Since then, unseasonably warm temperatures have helped settle the recent storm snow. The recent snowfall adds to the complexity of the snowpack, especially on cooler northerly slopes. The deeper early season snowpack consists of alternating layers of decompossing melt/freeze crusts and faceted sugar snow, which are poorly bonded and can be found below the new snow in the snowpack. In areas where the snowpack is exceptionally thin, large facet crystals can be found near ground. The persistent slab problem will likely continue for a while. With that in mind, it is important to assess the snow stability of the terrain before committing to ride. Evaluate the snow and terrain carefully and identify areas of concern.

Weather and CURRENT CONDITIONS
weather summary

Saturday thru Sunday - Dry conditions and above average temperatures are expected through the weekend with high pressure over northeast California and western Nevada.

Mon thru Tuesday - High pressure will begin to weaken late Monday as a shortwave passes north of the region. Ridge winds will increase Monday as the shortwave skirts across far northeastern CA with breezy surface winds. The main portion of the system pushes in Monday night through Tuesday with a cold front dropping through on Tuesday afternoon/evening. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny. Clear then becoming partly cloudy. Partly cloudy.
Temperatures: 47 to 53 deg. F. 27 to 35 deg. F. 49 to 55 deg. F.
Wind Direction: Light winds. Light winds. Light winds.
Wind Speed: Gusts up to 35 mph in the morning.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny. Partly cloudy. Partly cloudy.
Temperatures: 41 to 46 deg. F. 29 to 34 deg. F. 43 to 49 deg. F.
Wind Direction: Southeast Light winds becoming southwest Light winds
Wind Speed: 15 to 25 mph with gusts to 35 mph in the morning becoming light. 10 to 15 mph after midnight.
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer
This Avalanche Advisory is designed to generally describe avalanche conditions where local variations always occur. This product only applies to backcountry areas located outside established ski area boundaries. The information in this Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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