Eastern Sierra Avalanche Forecast - 4/1/14

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THIS AVALANCHE ADVISORY EXPIRED ON April 2, 2014 @ 10:11 pm
Avalanche Advisory published on April 1, 2014 @ 10:11 pm
Issued by Sue Burak - Inyo National Forest
bottom line

The avalanche danger is MODERATE on steep north and east facing slopes. Small human-triggered soft slabs, wind slabs and sluffing of the new snow are possible today in both exposed and sheltered steep terrain. Natural slides are unlikely.

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 on steep north and east facing slopes. Small human-triggered soft slabs, wind slabs and sluffing of the new snow are possible today in both exposed and sheltered steep terrain. Natural slides are unlikely.

  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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Moderate southwest to west winds formed wind drifts and soft slabs below ridgetops yesterday.  Winds were unusually calm last night and the snow that fell may have formed additional pillows of wind drifted snow. I expect last night's snow and yesterday's wind drifts and soft slabs will still be sensitive to human triggers today. With all the new snow, fresh wind deposits may be more difficult to identify- look for rounded, pillowy drifts. All upper elevation slopes have the potential to be wind drifted and cross loaded and will be found on north through east facing slopes, downslope from the ridgelines and above breaks in the slope.   

Avalanche Problem 2: Loose Dry
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Dry light snow that has not been wind hammered is a rare event each winter. Yesterday, observers reported easily triggered small to medium size loose snow sluffs in steep trees in the Sherwins. Cold temperatures last night and today will help keep the new snow dry and loose snow avalanches are possible today on slopes steeper than 335 degrees. A sizeable sluff could carry you into trees, rocks or over a cliff so pay attention to the terrain you are riding in.  

advisory discussion

Yesterday morning there was 15-18” of new snow above 9,000 ft in Rock Creek, the Mammoth Lakes Basin and the June Mountain area. Winds were light during the storm and with deep new snow, the most common avalanche observations were loose snow sluffs. June Mtn ski patrol reported a few soft slabs but mostly small sluffs. There was a slab avalanche reported in Solar Bowl in the Negatives and numerous long running loose snow slides that released during the storm.

The local mountains picked up 2” of water content over the last week, adding much needed water to the large existing deficit. The 2014 snow accumulation season  has ended up tied with the 2007 winter for the second driest since 1949 at Mammoth Pass. Storm totals for the last week of March range from 26” of snow with 2.4” water content at Mammoth Pass, 17-20”  at the Sesame Street study plot and 20 inches at 9,600 ft in Rock Creek.

The Monday night/Tuesday storm was a powerful spring storm and created a few avalanche problems.  Wind slabs will be an issue on exposed steep, upper elevation slopes. Control work on Mammoth Mountain produced some of medium sized soft slabs 12" deep.

Due to the deep amount of new snow, slopes do not need to be wind loaded in order to produce avalanches. A loose snow avalanche can carry you into rocks, trees or over cliff bands. As backcountry users it’s important to note that we are in the realm of human triggering today- there may be a lack of obvious signs of instability such as recent avalanches and cracking or whumpfing. Investigate each slope carefully before committing to steep terrain and always be thinking about the consequences of an avalanche.  

recent observations

Natural avalanche activity was reported yesterday morning on Mammoth Mountain. Ski patrol reported some 12" wind slabs were triggered off the top of Mammoth. June Mountain reported sensitive wind sluffs running long distances. Long running loose snow avalanches were reported in the Negatives and a slab avalanche occurred in the Solar Bowl. Loose snow sluffs were observed on north to northeast facing slopes below the Mammoth Crest.

Yesterday, stability tests done within the ski area on north facing slopes and in Rock Creek had similar results- the new snow fell apart under the shovel. Slabs were very soft and more like a sluff than a slab. Tests were done on slopes that were protected from the wind.  There was no whumpfing or cracking observed. Mountain slopes were obscured so it was hard to see if natural avalanche activity had occurred.

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 14 deg. F.
Max. temperature in the last 24 hours: 21 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: WSW mph
Maximum wind gust in the last 24 hours: 70 mph
New snowfall in the last 24 hours: 2 inches
Total snow depth: 60 inches
weather

Overnight, the mountains around Mammoth and June Mountains picked up another  2-3” of snow. This morning, light snow is falling and another inch or two could accumulate. Winds are breezy at the top of Mammoth Mountain, blowing from the southwest at 15-20 mph. By the afternoon, instability decreases as the storm moves east. Unsettled weather with occasional snow showers and below normal temperatures are expected Thursday and Friday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Tuesday Tuesday Night Wednesday
Weather: scattered snow showers snow showers mostly sunny
Temperatures: 27 deg. F. 18 deg. F. 32 deg. F.
Wind direction: SW N SE
Wind speed: 5-10 10-15 5-10
Expected snowfall: 1 in. 0 in. 0 in.
Over 10,000 ft.
  Tuesday Tuesday Night Wednesday
Weather: snow scattered snow mostly sunny
Temperatures: 27 deg. F. 14 deg. F. 32 deg. F.
Wind direction: S N SE
Wind speed: 10-15 10-15 5-10
Expected snowfall: 1-2 in. 0 in. 0 in.
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