Eastern Sierra Avalanche Forecast - 3/5/14

The backcountry is more accessible than it has been in years. Please help!  ... Click Here to Find Out How

THIS AVALANCHE ADVISORY EXPIRED ON March 6, 2014 @ 7:05 am
Avalanche Advisory published on March 5, 2014 @ 7:05 am
Issued by Sue Burak - Inyo National Forest
bottom line

The possibility of human triggered avalanches has diminished, however, people will still be able to trigger very isolated areas of wind drifted snow in steep alpine terrain where the snowpack is shallow. These isolated drifts vary over short distances. There is a pockety MODERATE avalanche danger today on slopes steeper than 35 degrees in the Mammoth and June Mountain areas. The avalanche danger is LOW in non windloded terrain and at mid-elevations in the trees. Wet snow slides are becoming larger and easily triggered with mild temperatures and warm nights.  

How to read the advisory


  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Bottom Line

The possibility of human triggered avalanches has diminished, however, people will still be able to trigger very isolated areas of wind drifted snow in steep alpine terrain where the snowpack is shallow. These isolated drifts vary over short distances. There is a pockety MODERATE avalanche danger today on slopes steeper than 35 degrees in the Mammoth and June Mountain areas. The avalanche danger is LOW in non windloded terrain and at mid-elevations in the trees. Wet snow slides are becoming larger and easily triggered with mild temperatures and warm nights.  

  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small
  • Trend ?
    Decreasing Danger

Normal caution is advised in the backcountry today. There has been no new avalanche activity for the past 4 to 5 days. The latest activity was on Saturday and Sunday, March 1 and 2 when heavy snowfall and high precipitation rates triggered many slab avalanches in the June Mountain area, the Mammoth Basin and Rock Creek.

Steep shaded slopes on north facing terrain hold dry snow and ECT tests resulted in fractures within the storm snow but no propagation in the Dry Creek area today. Watch for obvious signs of loading such as cornices, rounded drifts and rippled texture of the snow surface.  Avoiding slopes where these signs are present will be a simple way to stay out of trouble. 

Avalanche Problem 2: Loose Wet
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small
  • Trend ?
    Same

Thin high clouds over the last few days and strong March sun increases the energy reaching the snow surface, creating the snow surface to melt and warming the upper 1-4 inches of the snowpack. Night time temperatures are warming to close to freezing.  Many wet snow sluffs at mid- elevations are gouging into deeper layers or the ground where the snowpack is shallow. Wet snow sluffs have been occurring on steep north to south aspects at mid-elevations. Today, cloud cover will limit wet snow instability but if the sun comes out, instability will increase.

Avalanche Problem 3: Deep Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Trend ?
    Decreasing Danger

Deep slab avalanches are becoming more unlikely in the Mammoth Basin. In the Hourglass, an observer reported 200 cm of snow with facets at the base and multiple crusts throughout the old snow.  In places where the snowpack is shallow, the facets and depth hoar are rounding but still are reactive in tests, especially Rock Creek and the Punta Bardini area (http://esavalanche.org/content/punta-bardini-old-growth)

In the Rock Creek area, the total snowpack depth is a little over 2 feet compared to 6 feet in the Mammoth Basin. Half of the snowpack in Rock Creek from the ground up is well developed depth hoar that has been recently reactive in propagation tests. The persistent weak layer is an avalanche concern in gullies that have enough snow to ski. 

advisory discussion

Riding and skiing conditions remain good above 9,500 to 10,000 ft. in alpine terrain where wind and cooler temperatures are keeping the snow surface temperatures below freezing. However, even sun exposed slopes at high elevations especially around rocks, are susceptible to wet point release slides. With deep new snow, a small wet slide could dig down into weaker storm snow and potentially create larger avalanche. 

recent observations

An avalanche class reported a Rutschblock score of 3-4 on the layer between the storm snow and the old surface on Sunday above 9,700 ft in Rock Creek.

Steep shaded slopes on north facing terrain hold dry snow and ECT tests resulted in fractures within the storm snow but no propagation in the Dry Creek area today. 

On Monday, riders reported ECTN results at 10,400 ft in the lower T.J. Bowl area. The layer of concern was within the storm snow about 12 inches down from the surface. 

Riders in the Negatives reported 200 cmof snow in the Hourglass with facets at the bottom and multiple crusts under the storm snow. Rollers observed on high elevation east and southeast facing slopes.

 

Depth hoar and facets at bottom of 180 cm pit in the Earthquake Dome area.

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 35 deg. F.
Max. temperature in the last 24 hours: 44 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: 10 mph
Maximum wind gust in the last 24 hours: 50 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 58 inches
weather

After a nice mild sunny day on Tuesday, today will be cloudy and warm with southwest winds picking up this afternoon. Winds become stronger tonight, gusting to 45 mph.  A few inches of snow are expected to fall Thursday only aboe 10,000 ft. Light rain may fall at mid and low elevations tonight and tomorrow. There is the possibility of another storm reaching the area on Monday and Tuesday of next week. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: mostly cloudy clouds cloudy
Temperatures: 44-54 deg. F. 30-34 deg. F. 40 deg. F.
Wind direction: SW SW SW
Wind speed: 15-20 30-40 30-40
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: cloudy cloudy cloudy, possible snow
Temperatures: 40 deg. F. 28 deg. F. 40 deg. F.
Wind direction: SW SW SW
Wind speed: 25-30 45-50 50-60
Expected snowfall: 0 in. 0 in. 1-3 in.
Disclaimer

ESAC receives support from ...