Good morning, this is Sue Burak with the Eastern Sierra Avalanche Center with an avalanche advisory posted for Saturday, January 26, 2008. MOUNTAIN WEATHER Warm air advection pushed in by southerly winds, along with cloudy skies and high relative humidity brought yesterdays highs up about 8-10F. Today, highs will be around 30 F at the 8,000 ft elevation. Higher elevations will see high temperatures in the mid 20s, similar to Fridays temperatures. Lows will be in the mid 20 to upper teens. Southerly winds will be breezy today in the 15-25 mph range. Southerly winds will increase tonight and continue through Sunday. 40 to 60 mph winds will move a lot of snow on Sunday. Skies will be mostly cloudy today with a few snow showers. A winter storm watch has been posted for Mono and Inyo counties for tonight through Sunday night. Heavy snowfall is expected from Mt Whitney to the Tahoe area. The incoming low pressure system kicks the nuisance cutoff low to the east and should bring 1-2 feet of snow to elevations above 9,000 feet. Look for more typical snow densities in the 10% range for Saturday night. The Sunday night storm track favors Tahoe but the trend has been for lows to dig farther south than expected. In any event, Sundays snowfall will be drier and will be accompanied by strong winds. SNOWPACK AND AVALANCHE DISCUSSION Over the last week, 4 to 30 inches of snow has fallen above 9,000 feet from Virginia Lakes to Bishop Creek. Gem Pass picked up 3.5 inches of water, while Bishop Pass and Rock Creek picked up 4 inches of snow with 0.6 of water. Mammoth Pass picked up one inch of water while Cottonwood Pass picked up 17 inches of new and 1.5 inches of water. Erratic snow accumulation patterns make forecasting a real challenge. However, the common thread is the south wind of the last two days. Its all about the wind here in the eastern Sierra. The snowpack along the Sherwin Ridge produced significant avalanche activity yesterday. The powder clouds from avalanches in the Tele Bowls and on the Perch were reported Friday afternoon. Parties skiing out from June Mountain reported some slope settlement, as did a party skiing Chicken Wing. Settlement and collapsing were also reported from the Tioga Pass area on Thursday. With possible heavy snowfall on the way, remember that this weeks snow fell on suncrusts, wind board and settled powder. Snow was dry and light in all but wind exposed terrain, at least up until today when the upper 10 cm settled to form another density change in the pack. If one to two feet of heavy snow fall on the layer cake, something is going to give. The signs of instability are loud and clear- natural avalanche activity, slope settlement, collapses and cracking, then add continuing wind loading on a variety of aspects. The avalanche danger rating has gone from Considerable to HIGH in steep wind loaded terrain above tree line. The HIGH avalanche danger rating means natural and human triggered avalanches are likely. Unstable slabs are likely on a variety of aspects and slope angles. Given the unusual snow accumulation patterns, make sure you evaluate each slope you travel on. Avalanches may be triggered by a light load on any slope greater than 35 degrees. Since slope settlement, natural activity and collapsing is occurring in lower elevation terrain, the avalanche danger rating is CONSIDERABLE on steep wind loaded slopes from 8,000 to 9,500 feet. The snowpack along the Sherwin Ridge produced significant avalanche activity yesterday. The powder clouds from avalanches in the Tele Bowls and on the Perch were reported Friday afternoon. Parties skiing out from June Mountain reported some slope settlement, as did a party skiing Chicken Wing. Settlement and collapsing were also reported from the Tioga Pass area on Thursday. With possible heavy snowfall on the way, remember that this weeks snow fell on suncrusts, wind board and settled powder. Snow was dry and light in all but wind exposed terrain, at least up until today when the upper 10 cm settled to form another density change in the pack. If one to two feet of heavy snow fall on the layer cake, something is going to give. The signs of instability are loud and clear- natural avalanche activity, slope settlement, collapses and cracking, then add continuing wind loading on a variety of aspects. The avalanche danger rating has gone from Considerable to HIGH in steep wind loaded terrain above tree line. The HIGH avalanche danger rating means natural and human triggered avalanches are likely. Unstable slabs are likely on a variety of aspects and slope angles. BOTTOM LINE Given the unusual snow accumulation patterns, make sure you evaluate each slope you travel on. Avalanches may be triggered by a light load on any slope greater than 35 degrees. Since slope settlement, natural activity and collapsing is occurring in lower elevation terrain, the avalanche danger rating is CONSIDERABLE on steep wind loaded slopes from 8,000 to 9,500 feet. 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.