Eastern Sierra Avalanche Forecast - 4/9/14

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THIS AVALANCHE ADVISORY EXPIRED ON April 10, 2014 @ 7:20 am
Avalanche Advisory published on April 9, 2014 @ 7:20 am
Issued by Sue Burak - Inyo National Forest
bottom line

Clouds moved in overnight and morning temperatures above 9,000 ft range from 32 to 39 degrees. The snow did not get a good refreeze overnight and with get a chance to freeze. High clouds combined with April sun will make wet loose and wet slab avalanche possible today. Natural and human triggered wet avalanches are possible today.  Avoid being in or above terrain traps in steep northerly to southeasterly mid to high-elevation terrain. A MODERATE danger exists today for wet loose avalanches in northwest through southeast facing terrain above 8,500'. 

 

How to read the advisory


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

Bottom Line

Clouds moved in overnight and morning temperatures above 9,000 ft range from 32 to 39 degrees. The snow did not get a good refreeze overnight and with get a chance to freeze. High clouds combined with April sun will make wet loose and wet slab avalanche possible today. Natural and human triggered wet avalanches are possible today.  Avoid being in or above terrain traps in steep northerly to southeasterly mid to high-elevation terrain. A MODERATE danger exists today for wet loose avalanches in northwest through southeast facing terrain above 8,500'. 

 

  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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Poor overnight refreeze and high clouds will increase the amount of energy to melt the upper layers of the snowpack.The sun's warming effects will reach into steep high elevation north facing couloirs.  A poor overnight freeze, high clouds followed by sunny skies later today will continue the cycle of wet loose avalanches. 

Today avalanches will occur in suface snow and possibly at the new snow/ old snow interface. Small wet loose snow slides may step down into deeper layers and create a more serios avalanche that could knock a person off their feet or carry them over a cliff or into rocks. 

Increased winds forecasted for today will probably cool the snow surface in alpine terrain. Move to cooler or shaded slopes if you see pin wheels or rollers or the snow turns wet and sloppy. 

Avalanche Problem 2: Wet Slab
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Nights have been close to or above freezing the last three days. In Rock Creek, nights have been colder but I am concerned that several days of intense sun and warm temperatures will soon affect the depth hoar layer that is only 2 feet down from the snow surface. Wet slabs often occur when the snow surface melts and infiltrating water reaches the weak layer. When water comes in contact with weak faceted snow, the buried weak layer can be lose all strength and a wet slab avalanche can occur.  

The possiblity of wet slab avalanches exist in the Rock Creek area mostly on north facing slopes above 10,000 ft. 

advisory discussion

Warm weather and strong April sun resulted in a wet avalanche cycle on Sunday. Although most of the slides were small wet loose snow avalanches, there were several reports of large wet loose avalanches in the Pine Creek area. Some avalanches are stepping down into deeper layers of the end of March storm, creating much larger and potentially dangerous avalanches. Loose wet slides can start a thousand feet or more above you so avoid skiing or traveling under snowy/rocky cliff bands and terrain traps where a small loose wet slide could pile up many feet of dense avalanche debris. 

recent observations

Numerous loose wet snow slides were observed Sunday on east and southeast facing high elevation terrain in Rock Creek on Mt Starr and Pointless Peak. Isolated wet loose slides occurred on southeast slopes in the Negatives. 

A party reported wet loose avalanches on southeast slopes in the Pine Creek area. 

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 39 deg. F.
Max. temperature in the last 24 hours: 55 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 36 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 42 inches
weather

Clouds moved in overnight and morning lows are in the mid to upper 30's. Daytime temperatures will reach the 50's today and tomorrow before a slight cooling trend and a chance of snow reach the area Friday and Saturday. Breezy southwest winds in the 15-25 mph range are expected today at the 9,000 ft. elevations. Moderate winds are expected for terrain above 10,000 ft. with southwest wind 20-30 mph, gusting to 40. 

 

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: partly cloudy partly cloudy clear
Temperatures: 52-59 deg. F. 31-37 deg. F. 50-58 deg. F.
Wind direction: SW W W
Wind speed: 10-20 10-15 15-20
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: partly cloudy partly cloudy sun
Temperatures: 46-56 deg. F. 28-34 deg. F. 45-55 deg. F.
Wind direction: SW W SW
Wind speed: 20-30 20-25 10-20
Expected snowfall: 0 in. 0 in. 0 in.
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