June Mountain Area, Mammoth Basin Snowpack Summary - 2015-02-28 09:43

THIS ADVISORY EXPIRED ON March 2, 2015 @ 9:43 am
Avalanche Advisory published on February 28, 2015 @ 9:43 am
Issued by Sue Burak - Inyo National Forest
Avalanche Character 1: Wind Slab
Wind Slab avalanches release naturally during wind events and can be triggered for up to a week after a wind event. They form in lee and cross-loaded terrain features. Avoid them by sticking to wind sheltered or wind scoured areas.

Avalanche danger exists on slopes 35 degrees or steeper in exposed high elevation terrain on north facing slopes today. Human triggered avalanches are possible today.




Snowpack Discussion

This snowpack summary is for the June Mountain and Mammoth Lakes Basin. This summary will be updated tomorrow morning, March 1.

Last night, 4 to 6" of snow fell in the Mammoth area while a couple of inches fell on June Mountain. Winds were strong enough yesterday to blow a rider off his feet and down the Hourglass in the Negatives area. An observer from the Mammoth Lakes Basin reported wind transport of new snow along the ridge of the Red Cone Bowl along with numerous small thin wind slabs .

Another round of snowfall is expected by mid day with accumulations up to 6-8" in the high elevations of the Mammoth Basin and June Mountain by Sunday morning. Winds at the top of Mammoth Mountain are blowing around 40 mph. This is prime wind speed for wind slab formation in exposed terrain and in small features of complex terrain (see photo in Observations). Last night's snow has not had enough time to bond to itself and the old snow underneath. Additional snowfall today will increase the avalanche danger and human triggered avalanches are possible. Southwest and west winds will easily transport today's low density snow and form wind slabs that will be easy to trigger.

recent observations

This photo is from the Sawtooth Avalanche Center and is a excellent example of the distribution of wind slabs in complex alpine terrain. Expect similar conditions and wind slab distribution when skies clear tomorrow afternoon or Monday.

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: 20 deg. F.
Average wind direction during the last 24 hours: WSW
Average wind speed during the last 24 hours: 40 mph
Maximum wind gust in the last 24 hours: 67 mph
New snowfall in the last 24 hours: 5 inches
Total snow depth: 28 inches

Snow showers continue today with strong west and southwesterly winds blowing 30 to 40 mph range along the high ridges. Temperatures will reach the mid 20's today. Snowfall totals of  6 to 8" are expected by tomorrow morning.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Saturday Saturday Night Sunday
Weather: Clouds, snow showers showers scattered snow showers
Temperatures: 26 deg. F. 12-19 deg. F. 26-32 deg. F.
Wind direction: W N N
Wind speed: 10-15 10-15 20
Expected snowfall: 3 in. 5 in. 1 in.
Over 10,000 ft.
  Saturday Saturday Night Sunday
Weather: clouds and snow clouds and snow scattered snow showers
Temperatures: 17-25 deg. F. 9-15 deg. F. 18-26 deg. F.
Wind direction: W NE NE
Wind speed: 30-40 10-20 15-25
Expected snowfall: 3 in. 6 in. 4 in.

This snowpack summary applies only to backcountry areas outside established ski area boundaries. This snowpack summary only describes general avalanche conditions and local variations always occur. This snowpack summary expires 24 hours after the posted time unless otherwise noted. The information in this snowpack summary is provided by the USDA Forest Service who is solely responsible for its content.

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