Eastern Sierra - Thu Dec 31 2009
Eastern Sierra avalanche advisory
Posted December 31, 2009 by Sue BurakUpdated December 31, 2009 - 11:45 am
The avalanche danger for Thursday is estimated to be MODERATE in wind loaded terrain in the Mammoth Lakes Basin. Expect pockets of MODERATE avalanche danger off the north facing ridgetops in the June Lake backcountry and wind loaded terrain in the Rock Creek and Bishop Creek areas.
The Mammoth Lakes Basin picked up over a foot of snow in the last two days, and June Mountain received only a few inches. Rock Creek picked up 6 inches, South Lake 2 inches and Bishop Pass picked up over a foot of snow.
With the new storm snow and strong winds, firm, hollow feeling, styro-foam snow formed on lee aspects in alpine and open treeline zones along the Mammoth Crest. Several observers reported thin wind slabs from Tuesday night's wind events released with ski cuts on wind loaded terrain on the Mammoth Crest. Watch out for fat deposits of snow down the slope off ridgetops- this is where the slab is the thickest and easiest to trigger.
Thursday will be partly cloudy at the 8,000 to mountain top elevations. High temperatures will reach 40F in Mammoth and the mid 20’s at the higher elevations. Low temperatures are warmer by about 10-15F than lows a few days ago. Lows around the Mammothand June Mountain areas will be in the low to mid 20’s with colder temperatures from 8-15 F at the higher elevations.
The fast moving short wave trough that brought snow to the Mammoth area and the southern Sierra, moved east yesterday. Partly cloudy skies will prevail today in all locations.
Another shortwave trough will blaze across the northern Sierra on New Year’s Day, bringing a slight chance of snow to the Mammoth area. This drive by pattern of shortwave troughs bringing snow to areas north of Reno will continue through next week. The necessary ingredients for heavy snow in our area are not coming together at this point.
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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