Eastern Sierra - Fri Feb 19 2010
Eastern Sierra avalanche advisory |
| The avalanche danger rating for the entire region is estimated to be LOW. Over a week of dry weather and mild temperatures have continued to increase the stability of the snow pack. Mostly cloudy skies today will inhibit the surface melting concerns we’ve had over the past few days. The moderate winds yesterday and today may lead to very isolated pockets of wind-load at higher elevations, but due to the lack of available loose snow for transport, these will be hard to find. None the less, continue to use caution, especially near ridges in steep rocky areas where the snowpack is shallow. |
The main instability concern over the past few days has been surface snow warming and melting on East to South aspects. We observed mostly small natural wet point releases and roller-balls on these aspects on our tours in the Rock Creek area and Convict lake area. These tended to originate from shallow rocky areas. Reports from others are consistent with these observations in other areas as well.
Yesterday the winds picked up, and today the clouds have moved in, both of which will act together to inhibit this surface warming concern for the next several days. Even though the winds have picked up, due to the lack of loose snow available for transport, new wind-loading concerns will be minimal. While touring in the Mammoth Crest area yesterday almost no snow was observed to be blowing over ridges despite the moderate winds. However, this doesn’t mean that small isolated wind slabs will be impossible to find. Presently the snow surface is extremely variable, from areas of shelter soft snow, areas of smooth wind board, to melt-freeze crusts on solar aspects. When new snow does arrive, avalanche danger will increase, and will vary depending on the underlying old snow surface.
By: Sue Burak
The short term forecast for the next few days is coming together and we are expected to miss out on the precip party. The low pressure system off the West Coast will literally head south to Los Angeles and San Diego. The area will see scattered snow showers with little accumulation expected. The best chance for more than a couple of inches of snow will be Sunday night from a small weak system moving west from Idaho and dropping south over the area. The Owens Valley could see rain over the weekend and possible snow over the higher elevations of the southern Sierra.
Higher elevations cooled off a few degrees yesterday and mid elevations begin their cooling trend today. High temperatures in Mammoth and Aspendell will reach 40F today with lows tonight and Saturday night in the low 20’s. Temperatures fall on Saturday with highs only to reach 32F.
Elevations above 9500 ft will fall from the mid 30’s yesterday to the mid to upper 20’s today.
Skies will be cloudy with light southwest winds from 10-15 mph. Gusts up to 25 mph are expected over the ridgetops.
Look for a more active weather pattern to develop by the end of next week as the blocking ridge breaks down and opens the storm door.
Scattered small wet point releases and roller balls observed on east to south aspects.
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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