Avalanche Advisory: Saturday - Feb 6, 2021

THIS AVALANCHE ADVISORY EXPIRED ON February 7, 2021 @ 6:06 am
Avalanche Advisory published on February 6, 2021 @ 6:06 am
Issued by Steve Mace - ESAC

MODERATE avalanche danger exists at all elevations today due to the potential for a large a destructive persistent slab avalanche on northerly and easterly terrain. Wind slabs of varying size and sensitivity will also be possible to find on all aspects near and above treeline. Evaluate snow and terrain carefully and use terrain choice to mitigate your exposure to potential avalanches.

Thank you to everyone who was able to make it to our second virtual education event on the evening of February 3rd, focusing on Avalanche awareness, How to use the advisory, and a discussion about the current state of the snowpack. This event was recorded and is available to view on our YouTube page!

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.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    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 ?
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    Large
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A robust slab has been gaining strength and, in many areas throughout the range, resting on a weak and unconsolidated base. This is particularly true in the northern part of the forecast area. Managing this problem requires extensive evaluation and deliberate terrain choice. As the slab gains strength, it is becoming harder for humans to trigger persistent slab avalanches but it is important to remember that avalanches breaking on these lower weak layers have the potential to be large and destructive.  Northerly and easterly aspects are of greatest concern however we are not ruling out the broader distribution range of W-N-E-SE. Persistent Slab problems challenge our patience. Don’t be afraid to dig in and get a look at the lower layers of the snowpack to see if old snow is present in the areas you want to travel. Be wary of unsupported slopes and steep and shallow terrain where shallowly buried rocks may act as trigger points. Remember that persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities such as wind or storm slab and in some cases persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazards that may reside above you, and use terrain choice to limit your exposure.

Avalanche Problem 2: Wind Slab
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
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Wind slabs will vary in size and sensitivity today and may be present on all aspects near and above treeline.  Decreasing wind speeds may limit the potential for fresh slab development today, however, you can still expect to find fresh and sensitive wind slabs on southerly and westerly terrain, particularly in the high alpine. Lingering wind slabs on northerly and easterly terrain have been gaining strength and will be difficult for a human to trigger but they may have the potential to be quite large. Exposed areas and leeward catchment zones near and above treeline deserve elevated caution. Large drifts, recent cornice growth, and uneven snow surfaces are all clues that indicate nearby wind deposits. Be particularly suspect of unsupported and extreme terrain and be aware that warming temperatures and direct sun could loosen cornice features and small panels of wind slab.  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.

advisory discussion

Our current weather pattern will be a powerful draw to the backcountry enthusiast as we enter the weekend. It remains important to consider the complex nature of our snowpack if you decide to venture into the backcountry. Our persistent slab problem fits squarely into the category of “low likelihood and high consequence”, making it particularly hard to manage and predict. Variable and challenging surface conditions are also worth considering when evaluating your trip options today.

Check out our Observation Page for more detailed information on recent avalanche activity and snow conditions, and please consider posting your own field observations if you see anything interesting out there!

recent observations
Submit Snowpack Observations
Submit Avalanche Observations

02/05- Lee Vining Area- Wind effects in Lee Vining canyon

02/05- June Lake Area- Snow conditions on San Joaquin Mountain

02/05- June Lake Area- Snow conditions in the JMR backcountry

02/05- Mammoth Area- Wind affects, weak structure in the Lakes basin

02/05- Mammoth Area – Snow conditions and a Large natural avalanche, Hollywood bowl

02/05- Mammoth Area- Snow pit and poor structure, Panorama dome

02/05- Bishop Area- Recent avalanche activity and snow conditions on Mt Tom.

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2/04 – Mammoth area- Large avalanche, Hollywood bowl

2/04 – Mammoth area- Sherwin ridge, cornice collapse

2/04 – Mammoth area- Sherwin ridge, snowpack conditions

2/04 – Mammoth area- Sherwin ridge, variable surface conditions

2/04 – Mammoth area- Snow structure, MMSA backcountry

2/04 –Mammoth Area- Snow conditions, No name peak

2/04 – Mammoth area- Large avalanche, Bloody mtn

2/04 –Convict area- natural wind slab avalanche, Mono Jim Peak

2/04- Convict to McGee- Snow conditions

2/04- June Lake area- Snow conditions in the June Backcountry

2/04 -Rock creek- Snow conditions

2/04- Bishop area- Variable surface conditions, Habeggers

Weather and CURRENT CONDITIONS
weather summary

Expect Sunny skies and warm temperatures today. Highs in the mid 40°f are expected at lower elevations with temperatures approaching the mid to upper 30° f in the alpine.  Expect winds to continue out of the N today, maintaining light-moderate speeds with ridgetop gusts expected around 40 mph.

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. Sunny.
Temperatures: 40 to 46. deg. F. 25 to 31. deg. F. 38 to 46. deg. F.
Mid Slope Winds: North to northeast 5 to 15 mph. West around 15 mph with gusts to 25 mph. West around 15 mph with gusts to 30 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny. Clear. Sunny.
Temperatures: 33 to 39. deg. F. 25 to 31. deg. F. 31 to 37. deg. F.
Ridge Top Winds: Northwest to north 15 to 30 mph with gusts up to 40 mph. West 15 to 25 mph. West 15 to 25 mph with gusts to 35 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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