Eastern Sierra - Tue Mar 9 2010
Eastern Sierra avalanche advisory
Posted March 9, 2010 by Josh FeinbergUpdated March 9, 2010 - 10:46 am
The avalanche danger rating today for Bishop to June is MODERATE. New wind-slabs at low to high elevations are the main concern. Be especially cautious of these below ridge-lines on North to East facing slopes and on steep convex rollovers at mid to high elevations on a variety of aspects.
Strong winds at all elevations persisted from yesterday afternoon through last night. These winds were predominantly out of the South West, however swirling winds were observed at mid elevations, and observations made in the Convict Lake/Mini Morrison area yesterday afternoon revealed mostly easterly winds. 2-5" of new snow fell overnight, with the highest accumulation around the Mammoth area. Many areas of soft snow existed prior to last night/yesterday's new snow fall, meaning that even areas which did not receive much new snow were very susceptible to wind-slab formation. While touring around Mini Morrison yesterday afternoon some sensitive wind-slabs were already forming at all elevations. Even at lake level, a 6-8" crown resulted from triggering a slope failure on a small convexity at the edge of an aspen grove. Beware of new wind-load below ridge-lines (particularly on East to North facing slopes) and cross loaded slopes. Convex areas as well as areas at the edge of wind-slabs where the new snow load is thinner will be the easiest places to trigger slab avalanches today. Realize that these kinds of conditions have resulted in serious skier triggered avalanche accidents in the past in the Sierra. Please use good judgement!!
Expect partly sunny skies today, moderate winds predominating out of the North West which will be considerably calmer than yesterday, and continued cool temperatures.
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.
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