Eastern Sierra avalanche advisory

Posted December 26, 2009 by Sue Burak

Updated December 26, 2009 - 11:43 pm

The avalanche danger rating for today is estimated to be LOW. There are generally safe avalanche conditions but watch for pockets of unstable snow in very steep or windloaded terrain. Natural and human triggered avalanches are unlikely.

 

On Saturday, temperatures fell 10-15 degrees F from Christmas Day. Mid and low level clouds and an increase in relative humidity to over 60% transformed the snow surface in many places from the nice dry recrystallized powder of Christmas Day to a slightly moist snow surface on Saturday. A trace to about an inch of new snow fell in the Mammoth Basin and bonded well to the old snow surface. Skiing and riding conditions remain good in sheltered north facing terrain. Dense wind affected snow is found along north and south sides of ridges but these areas are not big enough in size for continuous slabs to develop despite the strong winds of December 23. The weather forecast calls for clouds and light snow showers for the next few days. This will inhibit surface hoar formation but the colder air temperatures result in more of a difference between the ground and the snow surface. Shallow snowpacks with a large change in snow temperature from the ground to the surface are the perfect candidate for faceted snow grains to form, even if the weather is cloudy and a little snowfall occurs. With no new snow, relatively calm winds and no change in stability test results, the avalanche danger rating remains LOW.

As a low pressure system moves across California today, isolated snow showers are expected at times for the next few days. The low pressure system is disorganized and can be seen undercutting the high pressure centered over British Columbia (http://squall.sfsu.edu/gif/sathts_pac500_00.gif). A few inches of snow could fall today. Temperatures will remain cold for the next few days with highs around freezing for the 8,000 to 10,000 ft elevation and the mid 20's for higher terrain. With cloud cover, low temperatures will not be as cold and lows in the upper teens and low 20's are expected. MJO activity is picking up in the Indian Ocean. It is possible the West Coast could see significant precipitation by mid to the end of January.