Eastern Sierra Avalanche Advisory - 1/14/18

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THIS AVALANCHE ADVISORY EXPIRED ON January 15, 2018 @ 6:19 am
Avalanche Advisory published on January 14, 2018 @ 6:19 am
Issued by Doug Lewis - Eastern Sierra Avalanche Center

The primary avalanche concern for Sunday (1/14) will continue to focus on Persistent Slabs due to several layers of weak faceted sugar snow within the snowpack.  Natural avalanches are unlikely, triggered avalanches are possible today, especially on northerly aspects near and above treeline where the snow remains 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
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The primary concern during the forecast period continues to focus on the Persistent Slab problem created by the wind event (1/10) with the associated Wind Slabs and recent storm snow (1/9) resting on a foundation of faceted sugar snow. The potential for failure is evidenced by recent reports of Whumphing on northerly aspects in the mid-elevations. If a failure occurs, it may propagate across the slope and possibly stepping down or eroding into the snowpack. Sudden collapsing is strong sign of instability. 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

High-pressure continues to bath the region in unseasonably warm temperatures and with the sun continuing to climb higher into the winter sky, the solar radiation is now strong enough to add some heat to the snowpack. The snow at lower elevations is receding and thinning in response to the recent warm spell while mid and upper elevations solar aspects have developed a melt/freeze crust that varies in maturity and supportiveness depending aspect, elevation, and solar exposure. The last snowfall we received was on 1/9, which 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 and Wind Slabs 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 melt/freeze crusts and faceted sugar snow, which are poorly bonded and can be found below the new snow in the snowpack. The recent reports of Whumphing near Duck Pass illustrate the complexity of the snowpack and the varied spatial distribution of the Persistent Slab problem. 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

Sun thru Monday - Mild and dry weather will continue through Monday with high pressure across the region. Temperatures will remain well above average with highs in the mid to upper 50s across western Nevada and Sierra valleys and relatively light winds.

Tuesday thru Wednesday - A trough off the west coast will weaken the high pressure ridge and allow the first in a series of storms to impact the region early Tuesday morning with upper level winds increasing by afternoon. Precipitation will begin to push into the northern Sierra by early Tuesday morning with the fast-moving cold front. Precipitation amounts remain meager with this storm (T-2”) from Mammoth north. The storm quickly pushes out of the Sierra and opens the storm door for the rest of the week. Wednesday will be a short break in between storms, along with a brief warm-up and breezy conditions. Winds will increase significantly late Wednesday night ahead of the next colder, stronger storm as a strong Pacific jet pushes into far northern CA. Sierra Crest gusts will easily reach 100+ mph with gusty surface winds.  

 

 

 

 

 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy. Partly cloudy then becoming mostly cloudy. Mostly cloudy.
Temperatures: 49 to 55 deg. F. 29 to 35 deg. F. 46 to 54 deg. F.
Wind Direction: Light winds. Light winds. Southwest
Wind Speed: Gusts up to 30 mph after midnight. 10 to 15 mph with gusts to 35 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy. Partly cloudy then becoming mostly cloudy. Mostly cloudy.
Temperatures: 43 to 49 deg. F. 29 to 34 deg. F. 40 to 46 deg. F.
Wind Direction: Light winds. Southwest Southwest
Wind Speed: 10 to 15 mph. Gusts up to 35 mph after midnight. 15 to 25 mph. Gusts up to 50 mph decreasing to 40 mph in the afternoon.
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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