Good evening, this is Sue Burak with the Inyo National Forest with an avalanche advisory update for Friday, January 23, 2009. MOUNTAIN WEATHER After a soggy day below 8,500 feet, mountain locations north and south of the Mammoth and June Mountain area will see scattered rain and snow showers Friday and increased precipitation by Friday afternoon. The Mammoth and June Mountain areas could see rain and snow all day Friday with snow levels above 8,500 ft. Expect another brief, short-lived storm Friday afternoon morning that could bring up to 8 inches of new snow to elevations above 10,000 ft. in the Mammoth area. June Mountain is expected to receive 4-6 inches of new snow with highs at the top of June Mountain in the mid 30s. Areas north and south of Mammoth and June could pick up 2-4 inches of new snow Friday afternoon. New snowfall will be wet and relative humilities will continue to be close to 100% in the Mammoth area while areas to the south and north of Mammoth will dry out Friday morning. Saturday will be mostly cloudy in Mono County with light southerly winds between 8,000 and 10,000 feet. Highs will be in the upper 30s at 8,000 ft with rain and snow likely on Mammoth Mountain and in the Mammoth Lakes Basin. Expect southwest winds in the 10-15 mph range with gusts up to 25 mph. These wind gusts have not able to transport much of the new wet snow around. For areas north and south of Mammoth in Mono County, Saturday will be partly cloudy with south and southwest winds blowing in the 10-20 mph range above 9,000 ft. The potential for heavier snowfall, as measured in feet rather than inches may arrive Sunday and Monday the potential of greater storm totals as measured in feet, approaches our area. This storm will arrive as a modified arctic air mass via British Columbia so expect highs to be in the upper teens and low 20s between 8,000 and 10,000 feet. Snow levels are predicted to be around 5000 ft. with this storm so snow may fall in the higher regions of the Owens Valley. SNOWPACK AND AVALANCHE DISCUSSION Although the rain and snow came in as the southern branch of the split flow, this did not translate into higher snowfall amounts and water contents in the southern Sierra. South Sierra locations above 9,500 feet picked up 3- 10 inches of new snow and an inch of rain in a heavy mixture of 12-15% snow density. The Bishop Creek drainage above 10,000 feet received about 6 inches of new snow with rain and snow water contents of 0.8 inches. It appears being at higher elevations did not mean lower density snowfall in the southern Sierra. Farther north in the Tuolumne Meadows and Rush Creek area, Dana Meadows picked up 10 inches of 15% density snow. Gem Pass at 10,700 feet in the Rush Creek drainage received 2 inches of water in the last 18 hours. Tioga Pass, always on the short end of the stick, picked up 6 inches of new snow. The Mammoth Mountain ski patrol study plot received 14-15 inches of new snow. Mammoth Pass on the south side of Mammoth Mountain at 9,300 ft received 0.8 inches of water and 14 inches of snow. If one believes the snow pillow data from this site, the top of Mammoth Pass received 14 inches of 6% density snow instead of the 12-18% density snow reported from Mammoth Mountain, June Mountain and Rock Creek. Reports from June Mountain indicate 10-12 inches of wet new snow accumulated at the top of June Mountain. Ski patrol reported hand charges released several medium sized avalanches releases on 35 degree slopes. These slides were big enough to bury or destroy a car or destroy a wood frame house. The patrol director told me these were wet slab avalanches that ran on the weak faceted snow in the pre existing snowpack. Touring today in the wet Mammoth Lakes Basin I found the new wet snow had bonded well with old snow surfaces. I was unable to get the new snow/old snow layer to fracture and propagate using the extended column test. I also used the stuffblock test to see if there was any weakness that could be detected in the snowpack. I did not get any results using the stuffblock test, even when dropping the 10 lb bag of snow stuff bag from a height of over 2 feet. This occurred from 9,000 to 10,000 feet in north facing glades. In shallow snowpack areas, the ice lens sandwiched within the depth hoar layer had lost some integrity. In places with 40-60 inches of snow, the weak layer and ice lens were seen at the base of the pack. This was also reported by the June Mountain ski patrol director. However, at the heavily instrumented meteorological station behind mid chalet on Mammoth Mountain, there is no sign that water moved through the 40 inch snowpack. Local variations always occur. For Friday, the avalanche danger is MODERATE. A MODERATE rating means there are locally unsafe conditions. These will be found on north facing slopes, 35 degrees and steeper that have accumulations of new snow greater than 8 inches. The MODERATE danger rating applies to the Mammoth and June Mountain/Negatives area. In areas receiving less than 6 inches of new snow, the avalanche danger rating is LOW with isolated pockets of MODERATE danger rating. These slopes will be steep (greater than 35 degrees) north facing slopes where more than 8 inches of new wet snow have accumulated. The avalanche danger will increase at the end of the weekend when a substantial, cold storm reaches the area. BOTTOM LINE For Friday, the avalanche danger is MODERATE. A MODERATE rating means there are locally unsafe conditions. These will be found on north facing slopes, 35 degrees and steeper that have accumulations of new snow greater than 8 inches. The MODERATE danger rating applies to the Mammoth and June Mountain/Negatives area. In areas receiving less than 6 inches of new snow, the avalanche danger rating is LOW with isolated pockets of MODERATE danger rating. These slopes will be steeper than 35 degrees) and north facing slopes where more than 8 inches of new wet snow have accumulated. Be aware that a weak layer is sitting at the base of the snowpack and a recent report told of whumping in a shallow snowpack on steep north facing slopes in the June Mountain area. 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. 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.