Eastern Sierra - Wed Apr 21 2010
Eastern Sierra avalanche advisory |
| MODERATE avalanche danger exists today on steep exposed wind loaded slopes at all elevations. Greatest concern exists for exposed convex slopes that face North to East, particularly below ridge lines at higher elevations. Also be wary of cross-loaded slopes and features such as gullies. |
8-12" of new snow fell throughout most of the forecast area yesterday and last night accompanied by strong winds out of the south west at low to high elevations.
Observations made in the Lakes Basin / Red Cone area of Mammoth yesterday evening revealed 1.5'wind drifts over the Tamarack cross country trails at 8500'. Ski cuts on the exposed upper portion of the North facing bowl produced limited small results, although there were areas with close to 2' of fresh wind load. 2small natural slab avalanches were observed mid-slope on east facing terrain on the skin up. Click here for more details.
Observations made in Rock Creek yesterday revealed 4-5" of new snow. Slabby conditions were found above tree line at the top of exposed gullies (10,800'). Ski cuts easily produced small 3-4" crowns which ran 75-100'.
Today snow is expected to continue in lighter amounts than yesterday. The winds are also expected to remain calmer with moderate gusts out of the West to West-North-West.
The Main avalanche concern for today is wind slabs. These will most likely be found and be most easily triggered on steep, exposed, convex slopes just below ridge lines that face North to East. Higher elevations are also of greater concern. As the day progresses and the winds shift out of the West-North-West,wind loading concern will develop on East-South-East facing slopes as well. Also be cautious of slopes that are cross-loaded.
Temperatures fell yesterday afternoon as the front moved in the region. Snow will continue in the mountain s of Mono and Inyo County today and tonight as the low shown here, http://squall.sfsu.edu/gif/sathts_pac_500_00.gif cuts off from the main flow and rotates bands of snow showers through the region today and tonight. By the time the low moves east on Thursday, the higher elevations in Mono and Inyo Counties could see 12-18” of new snow.
The higher elevations above 10,000 ft. will be cold. High temperatures might reach 20F today then warm a few degrees for a high of 28 on Thursday. Since the low is over us, ridgetop winds have dropped from Tuesday afternoon’s 50-80 mph to 20-40 mph for today. Winds have clocked around from the west southwest to the northwest as the low moves over us.
Mid elevations will be a little warmer with high temperatures reaching the mid to upper 20’s today. Expect gusty northwest winds up to 35 mph today.
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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