Eastern Sierra - Sun Mar 7 2010
Eastern Sierra avalanche advisory |
Human triggered avalanches are possible in steep terrain, and remember, it’s the small slabs that could get you today. Use extra caution on slopes steeper than 35 degrees with shallow, rocky areas or steep rollovers. |
An observer reported north winds stripping the north facing slopes on Red Cone yesterday. This experienced guide avoided the wind loaded starting zones off the top of Red Cone despite the stripping action of the north winds. He did not trust the rounded pillows off the ridge and all parties venturing into alpine terrain should also be suspicious of rounded, convex pillows of dense snow below ridgelines today.
North winds strip high elevation bowls in the Mammoth Basin. In the June Mountain backcountry, north winds load southeast facing slopes in the Negatives.Loading from north winds was the trigger for a large avalanche south of Solar Bowl in the Negatives this week.
Become familiar with the terrain and different slope aspects and slope angles before going out. This gives you an alternative plan in case your objective has fat rounded pillows off the ridge or at the top of the gully you plan to ski or ride.
Evaluate snow and terrain carefully today. For today, we expect touchy windslabs along exposed ridges and well as some crossloading on open bowls and in gullies.
The primary avalanche concern for today is windloading for all regions. Wind slabs are less sensitive to skier triggering than a few days ago, but it is still possible to trigger a slide today if you venture into steep terrain.
The secondary avalanche concern is weak snow at the bottom of the snowpack in areas south of Mammoth. There are no reports from the Rock Creek or Bishop area which could mean the layer has strengthened after the rapid loading from last weekend’s storm- or it could mean there are only a handful of people going out and tweaking only a few points in the snowpack. Watch out for possible trigger points - shallow, rocky areas, steep breakovers or wind-loaded areas where avalanches are commonly triggered.
A Pacific storm moved into the area last night and shifts east today. A brief
drying trend will be seen Monday before another storm moves into the area
on Tuesday. This system will split and redevelop over the Great Basin, giving
us a good chance of upslope snow showers. Temperatures will remain below
normal into the first part of the week. North winds will be light over the
ridgetops.
High temperatures at the 8,000 to 9500 ft elevation for the next two days remain cool, reaching 30-32 F. Higher elevations will be cold with highs in the upper teens. Lows will be in the mid to low teens for all elevations. Ridgetop winds will gust up to 35 mph this afternoon.
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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