Eastern Sierra - Sat Mar 13 2010
Eastern Sierra avalanche advisory |
The avalanche danger rating for the Mammoth and June Mountain areas today is CONSIDERABLE in all steep wind loaded north facing terrain between 30 and 35 degrees. Over a foot of new snow has fallen in the higher elevations and strong west to southwest winds continue to blow. Dangerous avalanche conditions exist and human triggered avalanches are possible today. For areas south of Mammoth that received 6” of snow or less, the avalanche danger rating today is MODERATE in wind loaded terrain steeper than about 30 degrees. |
June Mountain picked up 15” of new snow over night and Mammoth Mountain picked up 11”. Snow banners off the ridges are a sure sign that dangerous wind slabs await the over eager skier and rider today. The warm weather and clear skies on Thursday and Friday created surface crusts on exposed west and south to southeast slopes from 8,000 to 10,000 ft. Cold new, wind drifted snow will take some time to bond well to these icy surfaces.
In north facing terrain, dangerous wind slabs have formed, especially near the top of ridgecrests and on terrain features like cross loaded gullies. With the strong winds that have continued for over 15 hours, it is likely loading has occurred in the middle of slopes especially when cross loaded. Choose conservative terrain on this sunnyday after the overnight storm- small, well supported slopes, forestedareas, and low angle slopes not threatened from above. Avoid large, open slopes at treeline and above; steep,open slopes and gladesbelow treeline. If you want steeps today, it’s the resorts.
As promised, the storm dropped over a foot of snow at the higher elevations in the Mammoth and June Mountain areas. For today, partly cloudy to sunny skies are expected as the storm has moved east and southeast. The winds are the main weather story with strong winds blowing 30 mph at the 8,000 to 9,000 ft elevations with gusts up to 60 mph. The higher terrain along the Crest this morning is getting hammered with 40-60 mph southwest to west winds.
Wind direction will clock around to the north by mid day and expect gusts to 45 mph over the ridgetops by the afternoon.
It will be cold and windy today with temperatures with daytime highs barely reaching 30F at the 8500 ft elevation. Higher terrain will be cold with highs around 20F.
Tomorrow will be a dramatic change from today- temperatures increase 10-15F but the north winds will continue to blow in the higher terrain.
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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