Avalanche Advisory: Friday - Dec 27, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 28, 2019 @ 7:00 am
Avalanche Advisory published on December 27, 2019 @ 7:00 am
Issued by Steve Mace - ESAC

The Avalanche danger will be CONSIDERABLE at mid and upper elevations today, and MODERATE at lower elevations. A variety of wind slabs ranging from fresh and sensitive to old and stubborn will be the primary concern today on all aspects at mid and upper elevations. Storm instabilities will be less concerning, however still possible to find in more sheltered areas and at lower elevations. Particularly in areas north of June Lake.  Cautious route-finding and conservative decision making will be essential as you travel into the backcountry today.  

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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While the size and sensitivity will vary today, wind slabs sensitive to human triggers are likely on ALL ASPECTS at mid and upper elevations today. Fresh, sensitive wind slabs will be most prevalent on more southerly aspects while northerly and easterly aspects are harboring older, more stubborn wind slabs.  Expect continued slab development to occur on leeward slopes throughout the day today as moderate northerly winds continue to impact the area.  Do your own localized assessments and be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.   Surface clues such as blowing snow, dense drum-like snow, recent cornice growth, and uneven snow surfaces can help you identify and avoid areas of recent wind deposits.

Avalanche Problem 2: Loose Dry
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Loose-dry avalanches are likely on steep terrain today even in higher elevation areas that are typically more affected by the wind. Expect the size and distribution of Loose-dry avalanches to increase in areas north of June Lake where 12”+  of new snow fell over the last 48hrs.  Be particularly cautious in areas where terrain features increase the consequence of an avalanche. Steep confined gullies, creek beds, and mid-slope benches all pose an increased hazard.  While we typically think of sloughing as a relatively easy problem to manage, storm totals in some areas are over 2ft deep, and a resulting loose-dry avalanche in the wrong place today could certainly be large enough to bury a skier. 

Avalanche Problem 3: Storm Slab
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Storm slabs may be possible in areas that received a healthy dose of new snow over the last 48 hrs. While observations yesterday identified very loose and unconsolidated surface conditions, relatively warmer temperatures today may lead to settlement in the upper snowpack. Be on the lookout for signs of storm slab instability such as shooting cracks, wumphing, and recent avalanche activity, and be aware that even relatively small avalanche could entrain quite a bit of loose snow and potentially carry a skier through some unpleasant terrain. Heightened awareness is recommended in sheltered areas over 35°. 

 

advisory discussion

This week has brought ample new snow with storm totals ranging from 8-24” since Sunday the 22nd.  Also, the combination of colder than average temperatures and relatively light winds have helped to persevere the loose, low density, surface conditions throughout the range. While this has led to favorable ski conditions, it will be essential to remember that a variety of avalanche problems are present at all elevations and on all aspects today. Furthermore, the distribution of new snow is vastly different from the southern reaches of the range to the northern end. Do your own localized assessments, and don’t let the promise of soft snow and favorable weather today lure you into making bad decisions.  

Shifting winds and new snow may hide the typical surface clues, but it will be imperative to remember that dangerous wind slabs exist on all aspects. It is also important to keep in mind that the significant loose surface snow poses its own hazards.  Storm instabilities are on a healing trend. However, loose sloughing is continuing to pose a hazard, particularly in the northern reaches of the zone where storm totals are significantly higher. 

Low coverage is also a real concern today, particularly at lower elevations. In many areas, new snow has hidden otherwise obvious obstacles. Slow down and be cautious of lightly buried rocks, trees, and other sharks.

recent observations
Submit Snowpack Observations
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12/26- Virginia Lakes- New snow, light winds

12/26 - June Lake area - New Snow, Surface instabilities 

12/26 - June Lake area - Snow conditions on Chicken Wing

12/26 - Mammoth areea - Snow conditions on Mammoth crest

12/26 - Mammoth area - Snow conditions in the Sherwins

Weather and CURRENT CONDITIONS
weather summary

Expect Sunny skies and light to moderate northerly winds today as we get a break from the unsettled weather.  Colder than average temperatures will continue through the new year, with highs expected in the mid-20s at mid-elevations. Northerly winds may increase throughout the day with afternoon gusts expected around 50 mph on ridge tops.

 

Favorable weather will continue into the weekend, with a weak low-pressure system expected to impact the area late 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: Sunny. Clear. Sunny.
Temperatures: 25 to 31. deg. F. 11 to 16. deg. F. 30 to 36. deg. F.
Mid Slope Winds: North around 15 mph. Gusts up to 30 mph increasing to 40 mph in the afternoon. Northwest around 15 mph with gusts to 40 mph. Northwest 15 to 20 mph with gusts to 40 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Friday Friday Night Saturday
Weather: Sunny. Clear. Sunny.
Temperatures: 19 to 25. deg. F. 9 to 14. deg. F. 23 to 29. deg. F.
Ridge Top Winds: North 15 to 30 mph increasing to 25 to 35 mph in the afternoon. Gusts up to 50 mph. North 25 to 35 mph with gusts to 55 mph shifting to the northwest 15 to 30 mph with gusts to 45 mph after midnight. North 20 to 30 mph with gusts to 45 mph.
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 Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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