Eastern Sierra - Wed Feb 22 2012
Eastern Sierra avalanche advisory |
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The avalanche danger rating continues to be LOW today in the Mammoth Lakes Basin and the June Mountain sidecountry. Generally safe avalanche conditions exist. Natural and human triggered avalanches are unlikely except in isolated terrain features. Look for small areas of wet snow point releases and rollers this afternoon on east to southeast slopes. |
Morning temperatures are 5 degrees warmer than yesterday. The mid level clouds that heated the snowpack yesterday are mostly gone. Clear skies, light winds and warmer temperatures today will lead to some wet snow rollers and point releases around and below rocks and ridges on east to southeast facing slopes.
Our thin snowpack varies widely over the Mammoth Basin and Mammoth Rock. At high subalpine elevations on Duck Pass, an observer reported whumpfing in settled powder on Duck Pass and on steep side hills above Mammoth Creek. In contrast, in the Minaret Summit area on Monday, elevation 9,300 ft., a buried graupel layer showed up as the weak layer between last weeks storms and the old January snow in both compression and Rutschblock tests.
And to top it off, in the Mammoth Rock area, the storm slab from last week failed on facets above a crust on the January snow. There were very loose well developed facets below the crust. There were facets on the ground but not the large depth hoar previously observed in this area.
There were quite a few people out over the holiday weekend and no skier triggered avalanches were reported. It appears the variety of facets, graupel and whumpfing sounds are found in isolated terrain features which fits in the LOW danger level. Small avalanches might occur in isolated areas or in extreme terrain but generally safe avalanche conditions exist.
The strong ridge of high pressure will keep dry and mild weather in place over the region through Friday. Today will be the warmest day of the week with clear skies and 10,000 ft elevation temperatures warming to 30 to 36 degrees F. Lower elevations will reach the mid 40’s to low 50’s today. Clear cool nights are expected for the next few days, with lows in the mid to upper 20’s. North winds will continue to blow in the 30-40 mph range over the ridgetops today.
By Thursday, north winds pick up and temperatures drop about 10 degrees. A change to cold winter temperatures will begin this weekend as the ridge off the coast shifts north to the Gulf of Alaska and a trough digs down the West Coast.
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Please note that the avalanche danger rating in this advisory expires in 24 hours. This advisory is our best interpretation of snow pack conditions and NWS forecasts issued today. Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone exists between upper and lower elevations. Avalanches do not happen by accident and most human involvement is a matter of choice not chance. Most avalanche accidents are caused by slab avalanches that are triggered by the victim of member of the victim's party. Even small slides can be dangerous. Always practice route finding skills and carry avalanche rescue gear. Remember that avalanche danger ratings are only general guidelines. Distinctions between geographic areas, elevations, slope aspects and slope angles should be made.
