Eastern Sierra Avalanche Forecast - 3/19/14

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THIS AVALANCHE ADVISORY EXPIRED ON March 20, 2014 @ 7:05 am
Avalanche Advisory published on March 19, 2014 @ 7:05 am
Issued by Sue Burak - Inyo National Forest
bottom line

The avalanche danger is generally LOW for the Mammoth BAsin, the June Mtn backcountry and Rock Creek. Small patchy ares of wind drifts formed during Monday's wind event and are found below ridgetops and along rock ridges in the Mammoth Lakes Basin. As the sun warms the snow, it will change the snow properties and loose wet avalanches might occur in steep east to southeast facing slopes in alpine terrain. Even with the cool temperatures expected today, solar input and a lack of wind will soften the snow surface so watch out for small wet loose slides around rocks and below cliffbands.

The avalanche rose is filled out for alpine (above treeline) and mid elevations in the trees. Areas that are gray do not have snow or there is no snowpack information.

How to read the advisory


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

Bottom Line

The avalanche danger is generally LOW for the Mammoth BAsin, the June Mtn backcountry and Rock Creek. Small patchy ares of wind drifts formed during Monday's wind event and are found below ridgetops and along rock ridges in the Mammoth Lakes Basin. As the sun warms the snow, it will change the snow properties and loose wet avalanches might occur in steep east to southeast facing slopes in alpine terrain. Even with the cool temperatures expected today, solar input and a lack of wind will soften the snow surface so watch out for small wet loose slides around rocks and below cliffbands.

The avalanche rose is filled out for alpine (above treeline) and mid elevations in the trees. Areas that are gray do not have snow or there is no snowpack information.

  • 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

Monday's north winds stripped some north facing slopes in the Mammoth Basin and formed small wind drifts on other north facing slopes in alpine zones. Cross loading occurred on a few northeast and east facing slopes.  While these small drifts have a patchy distribution and don't pose much of an avalanche problem, watch for these areas in unusual places on slopes. 

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

As the sun warms the snow, it will change the snow properties and increase the potential for wet loose avalanches. Even with the cool temperatures expected today in alpine terrain, solar input and a lack of wind could increase loose wet snow activity.

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

Deep instability still lingers on steep north facing slopes in alpine areas. It would take a huge trigger like a cornice drop to activate this layer. The other potential trigger is snow melt trickling down through the pack.

recent observations

A snowpit dug in steep north facing terrain around 11,000 ft in the Rock Creek basin over the weekend revealed a 4 inches thick layer of huge depth hoar and chains of depth hoar up to an inch

long. This layer collapsed in ECT tests at 29 taps. Snow temperatures ranged from -4C at the snow surface to -10 C in the upper part of the snow pack.

This is a good reminder that weak snow still exists at the bottom of the snowpack- hard to trigger but a lyer to watch out for in the spring.

 

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 22 deg. F.
Max. temperature in the last 24 hours: 35 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: 20-25 mph
Maximum wind gust in the last 24 hours: 30 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 0 inches
weather

Sunny days and cold nights are expected for the week. Light southwest winds gusting to 30 mph are expected in alpine terrain while mid elevations will have light breezes 10-15 mph. 

A trough approaches the area next Tuesday with a chance of rain and snow. It's a week out and forecaster confidence will improve at the end of the week. March is typically a wet month so let's hope a normal March weather pattern prevails as spring approaches.

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: sun clear sun
Temperatures: 42-50 deg. F. 22-28 deg. F. 43-51 deg. F.
Wind direction: SW SW SW
Wind speed: 5-10 5-+10 15-20
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: sun clear sun
Temperatures: 32-37 deg. F. 22-25 deg. F. 32-38 deg. F.
Wind direction: SW SW SW
Wind speed: 10-20 20-25 20-25
Expected snowfall: 0 in. 0 in. 0 in.
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