Good morning, this is Sue Burak with the Inyo National Forest Eastern Sierra Avalanche Center with an avalanche advisory for Friday, January 30, 2009. MOUNTAIN WEATHER The weather will continue to be clear and dry for another week. Temperatures at the 8,000 ft elevation will be in the mid 40 degree range with a possibility of reaching 50 F today. Elevations above 9,000 ft will continue to be in the mid to upper 30s and the high elevations will have highs right around freezing, 32 F. Night time lows will be in the low to mid teens. Some locations with cold air pooling will continue to see lows in the single digits. Temperatures will cool off a few degrees on Saturday with gustier winds. The northeast winds continue today and with a system moving across northern California, the upper elevation winds will probably switch to the southeast later today. 8,000 to 10,000 ft wind speeds will be 10-15 mph with gusts in the 25 mph range. Above 10,000 ft, stronger northeast wind speeds of 20-30 in the morning will become lighter and from the southwest in the afternoon. Expect west winds on Saturday and northwest on Sunday. Temperature inversions increase on Sunday with valley locations colder than the mountains. SNOWPACK AND AVALANCHE DISCUSSION The snow quality is quite good in the Mammoth and June Mountain regions. There is some wind affected snow off the ridgetops, especially in the Negatives, parts of the Sherwin Bowl Ridge and off the Mammoth Crest. All of the Negatives chutes show crown faces from avalanches that occurred during the storm- some of these avalanches released in the old snow layer. The snowpack is shallow and it is not possible to ski farther north than Yost Meadow. Snow stability/instability tests show some weakness in the new snow, though test results show increasing stability the last two days. There is a definite boundary between the old and new snow in most locations below 10,000 ft- this is easily seen in a snowpit or feels like a solid layer with a ski pole probe. The layer is a high integrity, hard ice lens about an inch thick. The change in temperature between the ice lens and the ground is quite large and the old snow is losing strength rather than gaining strength. Continued daytime temperatures in the low to upper 30s and high energy losses during clear and cold nights will support the strong temperature gradient. The snow above the lens is also cold but warms to -3 and -4C in the upper 10-15 cm in the early afternoon. The instability within the new snow is a small density and grain size/type change about half way down in the new and well settled snow. In both shallow and deep areas, large faceted grains and depth hoar at the base of the snowpack are out of sight, out of most peoples minds, but remains weak. Because of this variability in the weak base layer, maintain good travel practices one at a time, always keep your partner in sight even on slopes where you dont find evidence of wind slabs. Today the avalanche danger is estimated to be MODERATE on steep, high elevation, wind affected slopes from the eastern end of the Sherwins north to June Lake. These are slopes 35 degrees and steeper and range from southeast to northwest aspects. Shallow and easily triggered wind slabs are found below ridgetops on southeast to north facing slopes right above tree line. On other slopes, the avalanche danger is estimated to be LOW. The gusty nature of the winds means some mid-slope features have been windloaded and some gullies are cross-loaded. While winds have been from the northeast, there has been minimal to moderate wind transport off the north facing slopes and new snow remains dry with some wind affected snow off the tops of ridges. The Tuolumne Rangers sent this report Wednesday night. Weather: (January 22 through January 28) High temp: 48° (Jan 27) Low temp: -7° (Jan 26, 27) New Snow: 25 (Jan 22 through Jan 25) Total settled snow depth: 29 as of January 28 Ski Conditions and Weather: We had a little of everything this past week; rain, snow, slush, sunshine. It started out as a rain/snow mix, then turned to all snow once the temperatures dropped. We ended up with 25 inches of new snow with a water equivalent of 2.67 inches. We are now under high pressure again with intense sunshine and east winds. We saw one natural avalanche up near Tioga Pass on an east facing slope and some wet slides on the granite domes. Not sure what the bonding of these two distinct layers are going to be, so caution is advised on the steeper slopes. Above 9500 feet there is more snow since our rain event didnt extend that far up. We are seeing in excess of 60 inches of snow at that elevation compared with just 30 inches 1000 feet lower. Trail breaking is still difficult as the snow just collapses under our weight. The amount of water in the snowpack at Mammoth Pass is 40% of what it is supposed to be on April 1. The snowpack would have to pick up 26 inches of snow water equivalent in February and April which is more water than is contained in the snowpack today. Estimates are we would need upwards of 25 feet of snow to fall between the end of January and the end of March; that gets less and less probable with each passing day. South of Mammoth the snowpack averages between 20-35 inches in depth which is less than half the depth of the snowpack in the Mammoth Lakes Basin. BOTTOM LINE Today the avalanche danger is estimated to be MODERATE on steep, high elevation, wind affected slopes from the eastern end of the Sherwins north to June Lake. These are slopes 35 degrees and steeper and range from southeast to northwest aspects. Shallow and easily triggered wind slabs are found below ridgetops on southeast to north facing slopes right above tree line. On other slopes, the avalanche danger is estimated to be LOW. The gusty nature of the winds means some mid-slope features have been windloaded and some gullies are cross-loaded. While winds have been from the northeast, there has been minimal to moderate wind transport off the north facing slopes and new snow remains dry with some wind affected snow off the tops of ridges. The avalanche danger rating is only a starting point. YOU CONTROL YOUR OWN RISK by choosing where and when you travel. Please note that the avalanche danger rating in this advisory expires in 24 hours. 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.