Eastern Sierra - Sat Jan 2 2010
Eastern Sierra avalanche advisory
Posted January 2, 2010 by Sue Burak
Generally stable avalanche conditions. Natural and human-triggered avalanches unlikely. The avalanche danger rating is estimated to be LOW today. Small avalanches could occur in isolated areas or extreme terrain.
Conditions in the mountains will remain fairly constant for the next few days with no precipitation and air temperatures in the 40’s.
The warm temperatures and wind have created what one might generously call variable snow surface conditions – wind pack, damp powder and crusts. There is some cold dry snow on sheltered, mid- to upper-elevation slopes away from exposed ridgelines, but the snowpack is getting thin on most slopes below 9,000 ft.
The Bishop Creek and Rock Creek basins have snowpacks ranging from less than a foot to close to 2 feet in wind deposition zones. The shallow snowpacks are faceted and weak throughout and have thin suncrusts. The weak snow does not support skis around rocks and rocks are sprinkled generously on all slopes.
The sparkly small to medium snow crystals on the snow surface these days can be surface hoar or recrystallized snow. Some lines on north facing slopes in the trees make a hissing sound as skis or snowboards move through it. You will find this recrystallized snow on shady slopes or slopes with weak sun. It weakens the snow surface and can persist for a week or more. This surface layer could become a weak layer in steep trees once we get into a storm cycle. It might take more than a week, but snow is sure to come in January- isn’t it??
High clouds yesterday and building high pressure brought the warmest daytime temperatures in over a week. Most remote stations located above 9,600 ft, reached close to 40 degrees F yesterday.
Expect another cold morning in areas where cold air pools, like Rock Creek , Slide Canyon and McGee. Other locations from 8,000 to 11,000 ft will see morning lows in the mid 20’s.
For the next few days, there will be more sun and possibly very few clouds. Highs will be in the upper 30’s and low 40’s for higher elevations and the Mammoth and Aspendell elevations could reach the mid 40’s today and for the rest of the week. Winds will be light today and from the southeast at mid elevations from 8,000 to 10,000 ft. Higher elevations will see west winds with occasional gusts to 35 mph.
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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