Mammoth Basin Snowpack Summary - 2015-04-29 07:31

THIS ADVISORY EXPIRED ON May 2, 2015 @ 5:31 am
Avalanche Advisory published on April 29, 2015 @ 7:31 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 sun and warm temperatures today could trigger a rash of loose avalanches as the snowpack surface warms.

Snowpack Discussion

Over the next week, above freezing temperatures and strong late April sun will quickly spike the avalanche danger as the snow surface gets wet.

For the last three days the new snow that fell on Saturday has become warmer and wetter each day. Warm skies last night put a dampening effect on radiational cooling, and low temperatures that barely reached 32 degrees froze the upper layers but probably did not provide enough cooling for a deep, solid refreeze.  This thin crust should melt quickly and stability will rapidly deteriorate because the snow underneath did not freeze and remains weak and wet.

The best places to ski and ride today are north facing slopes at the highest elevations with dry snow. Pick your terrain carefully- steep confined gullies could turn into terrain traps if a wet slide starts above you. Point release slides from cliffs, rocks out crops have the potential to knock you down and drag you into terrain traps. To get there and back, avoid avalanche runout zones especially if you see any pinwheels of snow rolling downhill. More wet avalanches expected today.

The last snowpack summary will be posted on Saturday morning, May 2.

recent observations

The strong north winds after the storm stripped snow from the top of the Red Cone but left deposits of wind drifted snow in the bowl below the ridgetop.  To the east in the Hammil Bowl area, 6 to 8 inches of wet new snow showed little sign of wind stripping on northwest to northeast slopes from 10,000 to 11,000 ft. Instead, a fairly uniform 6 to 8 inch layer of wet snow from the recent storm was found above 10,000 ft.

Many point release loose wet slides had occurred on Monday and point releases were rolling down the high elevation slopes in the Hammil Bowl area.

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 33 deg. F.
Max. temperature in the last 24 hours: 50 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 40 mph
Maximum wind gust in the last 24 hours: 60 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 0-12 inches

This morning’s overnight low temperatures are a degree or two above freezing at Mammoth Pass and even warmer at 36 degrees at the 10,700 ft. elevation on Gem Pass. Southwest winds are blowing steady at 35-40 mph at the summit of Mammoth Mountain.  

Daytime highs will reach the low 60’s today at the 9,000 to 10,000 ft. elevations with gusty southwest winds. High elevation terrain will be warm with highs reaching the mid 50’s with southwest wind gusts reaching 40 mph. Skies become partly cloudy tomorrow with a chance of thunderstorms occurring in the afternoon.   

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: sunny clear sun with afternoon clouds
Temperatures: 60 deg. F. 40 deg. F. 60 deg. F.
Wind direction: SW SW N
Wind speed: 15-20 10-15 20-30
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: clear clear partly cloudy
Temperatures: 45-50 deg. F. 30-35 deg. F. 45-57 deg. F.
Wind direction: SW N N
Wind speed: 25-30 20 20-35
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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