Eastern Sierra Avalanche Forecast - 2/2/14

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THIS AVALANCHE ADVISORY EXPIRED ON February 3, 2014 @ 7:10 am
Avalanche Advisory published on February 2, 2014 @ 7:10 am
Issued by Sue Burak - Inyo National Forest
bottom line

The avalanche danger is moderate at middle and upper elevations in the Mammoth Lakes Basin. Human triggered avalanches are possible on steep terrain where storm snow and wind drifts  exist above crusts and weak faceted snow. You can also trigger avalanches on steep shaded slopes at and below treeline where weak faceted snow comprises the lower half of the snowpack. Avoid consequential terrain and slopes steeper than 35 degrees.  

How to read the advisory


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

Bottom Line

The avalanche danger is moderate at middle and upper elevations in the Mammoth Lakes Basin. Human triggered avalanches are possible on steep terrain where storm snow and wind drifts  exist above crusts and weak faceted snow. You can also trigger avalanches on steep shaded slopes at and below treeline where weak faceted snow comprises the lower half of the snowpack. Avoid consequential terrain and slopes steeper than 35 degrees.  

  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Persistent Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Trend ?
    Same

Over a foot of new snow is sitting on weak faceted snow 12 to 18” below the surface. Reports of whumpfing and collapse in the Mammoth, Rock Creek and June Lake area confirm that this layer is weak and susceptible to collapsing several days after the storm. Below normal temperatures ensure the change in temperature from the snow surface exposed to cold air to the warm ground will continue and will continue to drive the faceting process. This layer needs to be treated with respect because human triggered avalanches are still possible, especially in areas where shallow snow at the edges of gullies blends into “deeper” snow- well at least for this winter, anything over 12 inches is “deep”.

advisory discussion

Avalanche forecasting relies on collecting diverse data, including but not limited to, snowpack data. The data we look for tells us about the state of the snowpack- the best data does not have to be interpreted. Things like recent avalanches, whumpfing and cracking are clear signs of instability.  Whumpfing and collapsing today is a clear sign that in some areas, the snow is unstable. Since whumpfing is occurring on flat ground, low angle slopes and in some cases, slopes steeper than 30 degrees, avoid steep north facing slopes at and above treeline.

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 1 deg. F.
Max. temperature in the last 24 hours: 11 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 20-25 mph
Maximum wind gust in the last 24 hours: 27 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 24 inches
weather

Below normal temperatures keep daytime highs in the 20’s through the middle of this week. Night time temperatures will reach 0 F and below this week. Today will be cloudy with scattered snow showers but little accumulation is expected. There is a good chance that measurable snow will return next weekend.

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: clouds clouds clouds
Temperatures: 22 deg. F. 10 deg. F. 24 deg. F.
Wind direction: SW N W
Wind speed: 5-10 5 15
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Sunday Sunday Night Monday
Weather: clouds clouds clouds
Temperatures: 21 deg. F. 12 deg. F. 23 deg. F.
Wind direction: sw n w
Wind speed: 5 5 10-15
Expected snowfall: 0 in. 0 in. 0 in.
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