Mammoth Basin Snowpack Summary - 2015-02-25 07:01

THIS ADVISORY EXPIRED ON February 27, 2015 @ 7:01 am
Avalanche Advisory published on February 25, 2015 @ 7:01 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.

Small windslabs will be found below ridgetops in the Mammoth Basin. Isolated areas of wind slabs will also be found in the June Mountain area.

Snowpack Discussion

In the June Mountain area, winds blowing from the northeast over Mono Lake created 14-18+ inches of cold dry snow early Monday morning on June Mountain and the Negatives. On Monday, ski cuts on June Mountain produced small dry wind slabs that popped of the old rain surface and ran farther than usual. It’s important to remember that fracture character- the sudden planar and sudden collapse fracture qualities indicate unstable snow exists and should be considered at your decision point in determining whether to ski a particular slope.

Mammoth Mountain and the Mammoth Lakes Basin picked up only 8 to 10” of new snow on Monday morning and by Tuesday afternoon, snow had settled 2-4”. Northeast winds on Monday and yesterday were not strong enough to strip snow off of north facing slopes along the Mammoth Crest, though numerous snow devils formed on and below the Crest. There have been no reports or observations of natural or skier triggered avalanches.

On north to east facing slopes in the Red Cone area, areas of wind loading were observed on north facing slopes. During the storm, winds were from the southwest and west and the beginnings of small cornices were found along parts of the Mammoth Crest. Given moderate wind speeds, areas of wind loading to do not appear to be widespread. Reports from the Negatives indicate the entrances to gullies are wind affected but dry snow is found below the entrances. 

Wind pillows are easy to find- look for areas where the surface snow texture is rippled and the snow underfoot is thicker. There is enough new snow that skis do not reach the old crusts and layers from the early February storm. You should be thinking about what the danger is on the slope they plan to ski. Use non-digging field observations such as whumpfs, ski penetration, hand shear and ski pole probes.  

The next snowpack summary will be posted Friday morning, February 27.

recent observations

After a cold morning yesterday, air temperatures and strong end of February conspired to create irritating skin clogging conditions on all aspects in the Lakes Basin.  Funnels of snow, or snow devils spun up from the snow surface around Jaws and Blue Crag. The recent snow has bonded to the old snow surface at mid elevations. Snow is dry and cold above treeline.

Compression tests showed moderate results on the old snow/new snow layer but extended column tests did not propagate and did not confirm the weakness produced by the compression test. Depth hoar and facets and crusts exist at the bottom of the snowpack.

CURRENT CONDITIONS Weather Observations Between June (10,000 ft.) and Mammoth (11,000 ft.)
0600 temperature: 24 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: 40 mph
Maximum wind gust in the last 24 hours: 60 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 26 inches

This morning mountain temperatures are in the 20’s with northerly winds blowing 20-30 mph under mostly clear skies. Today will be sunny until later in the day when increasing clouds from an approaching cold front approaches the area. Today will be the warmest day of the week with daytime temperatures a degree or two higher than Tuesday.

By Thursday, clouds increase with increasing chances of snowfall occurring in the Friday and Saturday time period. By Saturday night, another upslope flow event is possible, bringing more dry snow to the June Mountain area.  

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: mostly sunny mostly clear chance of snow
Temperatures: 44-46 deg. F. 25 deg. F. 44 deg. F.
Wind direction: NW NW N
Wind speed: 10-15 10 10-15
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Wednesday Wednesday Night Thursday
Weather: mostly sunny partly cloudy chance of snow
Temperatures: 40-43 deg. F. 23-25 deg. F. 38-40 deg. F.
Wind direction: NW NW N
Wind speed: 15-25 10 10-15
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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