Mammoth Basin Snowpack Summary - 2015-04-18 09:02

Avalanche Advisory published on April 18, 2015 @ 9:02 am
Issued by Sue Burak - Inyo National Forest
Avalanche Character 1: Loose Wet
Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.

Strong late April sun continues to heat the new snow that fell last week in the Mammoth Basin and Tioga Pass area/ Snow found at the high elevations and wide open terrain of the Tioga Pass area is slower to transform than in the Mammoth Basin due to night time cooling of the snowpack. East and southeast slopes are firm in the morning but by mid afternoon, are wet and shear easily under skis and snowboards.  Avoid steep slopes in the afternoon when rollers travel downslope from your tracks and wet ''surfing" snow conditions appear.

Snowpack Discussion

This snowpack summary covers the Tioga Pass area.

Snow conditions in the Tioga Pass area yesterday resembled eating at a buffet in a Nevada casino. Spring corn snow in the valley bottons; hard, icy north aspects that had been raked by last week's north winds, areas of scalloped soft settled powder in steep north facing terrain, lots of damp to wet snow in transition to spring conditions from snow that fell during last week's storm- also known as mank- and icy breakable crusts. Numerous wind slab avalanches that fell during and after last week's snowfall were evident in steep north and northeast facing cirques. Snow coverage is sparse and many gullies and couloirs that are usually filled in now end in short cliff bands, adding adventure to descent route selection.

By afternoon, southeast and east facing slopes were wet and numerous loose point releases were common. Snow that fell last week is getting wet and forms a 30 cm slab overlying a firm layer.  The possibility of wet snow avalanches on east and southeast facing slopes in the Tioga Pass area should be on your mind if traveling in the area.

The upcoming week of unsetttled, cloudy weather will impact all aspects with lots of energy coming from the sun and clouds. Southeast and east facing terrain is the primary area of wet snow avalanche concern.  




recent observations

Snow coverage in the Tioga Pass area is thin. The popular slope on False White is peppered with rocks. The thick February layer found about 30-50 cm from the snow surface was not observed in the areas we traveled yesterday but there is a wind layer formed in March that underlies recent storm snow. 

Snow depths above 10,500 ft. range from 80 to 150 cm on north facing slopes- some areas of soft settled, wind scalloped powder are found interspersed with large areas of north wind stripped icy surfaces.

Skiing condtions in Solstice and Ellery Bowl are reported to be variable.




CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 26 deg. F.
Max. temperature in the last 24 hours: 38 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: 25 mph
Maximum wind gust in the last 24 hours: 40 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 0-36 inches

Weather will be unsettled this next week with snow showers and thunderstorms possible through Friday.  Daytime highs above 10,000 ft. wil be in the mid 40's with overnight lows in the mid to upper 20's. Rain is also possible in the afternoons.

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: afternoon clouds cloudy chance rain or snow
Temperatures: 53 deg. F. 38 deg. F. 53 deg. F.
Wind direction: North NE calm
Wind speed: 5-10 5-10 calm
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Saturday Saturday Night Sunday
Weather: clouds afternoon cloudy clouds,chance of rain or snow
Temperatures: 44 deg. F. 32 deg. F. 45 deg. F.
Wind direction: North NE NE
Wind speed: 5-10 5-10 5
Expected snowfall: 0 in. 0 in. 0 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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