Avalanche Advisory: Friday - Jan 18, 2019

THIS AVALANCHE ADVISORY EXPIRED ON January 19, 2019 @ 6:46 am
Avalanche Advisory published on January 18, 2019 @ 6:46 am
Issued by Steve Mace - ESAC

Avalanche Danger will remain HIGH today at mid and upper elevations, and CONSIDERABLE at lower elevations.  Heavy snowfall and strong winds over the last few days have created a multitude of problems. Wind slab, storm slab, and persistent slab avalanches will be likely today. Hazardous conditions exist. With the high level of uncertainty, travel is NOT recommended in or below avalanche terrain. 

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Large wind slab avalanches will be likely today.  Strong southwest winds have accompanied the intense snowfall over the last few days. Resulting wind slabs will be large and very sensitive.  As the winds shift to the west today, expect fresh Slab development on more easterly terrain. While fresh wind slabs will primarily be a problem in exposed terrain at mid and upper elevations, extreme winds have distributed snow in unpredictable ways.   It will not be impossible to find wind slabs in more sheltered areas even at lower elevations.  Treat all leeward slopes as potentially loaded and sensitive.  Avoid being on or underneath slopes greater than 30°.

Avalanche Problem 2: Storm Slab
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While the intense snowfall from yesterday has eased off, the snowpack is still adjusting to the new load. Human triggered storm slab avalanches will be likely today.  In addition, fragile surface hoar has been confirmed in many areas buried under the new snow, increasing the sensitivity of storm slabs.  Shooting cracks, wumphing, and recent avalanche activity are all signs of instability.   Resulting avalanches are likely to be large, and caution should be taken in areas where the slope angle is greater than 30°.  

Avalanche Problem 3: Persistent Slab
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Prior to this past storm, multiple persistent issues have been noted in the snowpack.  Loose faceted snow continues to be found near the ground throughout the forecast area.  3-4' of new snow with a water equivalent of over 6" has been added to the snowpack this week. This is a considerable load to add to an already weak structure.  Resulting avalanches are likely to be very large and destructive, propagating long distances and traveling far into runout zones.  Even relatively small avalanches will have the potential to step down to these deeper layers creating a much larger avalanche.  Confidence in the sensitivity of these persistent slabs is low and care should be taken to stay far away from suspect slopes.

advisory discussion

As the holiday weekend approaches, we are entering a particularly dangerous time.   Mild weather and lots of fresh snow will make traveling into the backcountry enticing. However, the avalanche danger remains HIGH and avalanches today are likely to be very destructive and potentially unsurvivable.  Extreme weather has limited our ability to collect observations and forecaster confidence is low.  In times of high uncertainty, it is essential to increase your margins and limit your exposure.  When in doubt it is best to just avoid being in or under avalanche terrain

Weather and CURRENT CONDITIONS
weather summary

Expect to see cloudy skies and scattered showers today as more mild conditions return to the area. Temperatures are expected to reach into the mid 30's at upper elevations as the winds shift to the west and drop to moderate speeds, gusting to 60mph on ridge tops.   The clouds will begin to break this evening as the temperature drops into the teens, and the winds shift to the northwest.

 

We expect to see a brief spell of mild conditions tomorrow, marked by warm temperatures and light to moderate winds before another fast-moving storm moves into the area on Sunday. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%. Mostly cloudy then becoming partly cloudy. Partly cloudy then becoming sunny.
Temperatures: 30 to 40. deg. F. 24 to 29. deg. F. 35 to 45. deg. F.
Mid Slope Winds: West 10 to 20 mph. Gusts up to 40 mph. West 10 to 20 mph with gusts to 40 mph. Light winds.
Expected snowfall: up to 1" in. None in. None in.
Over 10,000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Slight chance of snow. Snow levels increasing to 7000 feet. Chance of precipitation is 15%. Mostly cloudy then becoming partly cloudy. Partly cloudy then becoming sunny.
Temperatures: 30 to 35. deg. F. 19 to 24. deg. F. 31 to 39. deg. F.
Ridge Top Winds: West 20 to 35 mph with gusts to 60 mph. Northwest 15 to 30 mph. Gusts up to 50 mph decreasing to 40 mph after midnight. West 15 to 20 mph with gusts to 35 mph.
Expected snowfall: Up to 1" in. None in. None 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 Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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