Eastern Sierra - Tue Jan 19 2010
Eastern Sierra avalanche advisory
Posted January 19, 2010 by Sue Burak
The avalanche danger rating is estimated to be HIGH today. Yesterday's intense southerly flow has created widespread areas of windslab susceptible to human-triggering in alpine and treeline locations. Natural avalanches and human triggered slides are likely in steep, windloaded, north facing terrain.
Over a foot of new snow fell yesterday in a short period of time and high snowfall rates came with strong to extreme southwest winds. Avalanche conditions are very dangerous and large avalanches could occur in many areas. Travel in avalanche terrain is not recommended today.
Another 8-16" of new snow is expected by this evening. Over a foot of new snow fell yesterday in a short period of time. Snowfall rates of 2-3 " per hour came with strong to extreme southwest winds. Avalanche conditions are very dangerous and large avalanches could occur in many areas. Travel in avalanche terrain is not recommended today.
The first in a long series of systems impacting our region moved across the Sierra yesterday. The equal opportunity storm dumped 12-17inches of new snow, with the Sierra south of Rock Creek receiving the greatest snowfall and water content.
The jetstream is racing across the Pacific in a zonal pattern from east Asia to northern Baja. Wind speeds are peaking around 220 mph. Several more storms are lined up and strengthening along the jet stream. This afternoon, our region will sit under a favorable location for orographic precipitation with southerly flow at the surface and aloft and 8-16" is expected to fall in the mountains from the Southern Sierra north to the Sonora Pass area.
For today, about 6-8 inches of new snow is expected above 9000 ft in Mammoth and June and above 8500 ft in the southern Sierra. Another brief break in precipitation is expected Tuesday night through Wednesday. High temperatures will be in the low 20's at all elevations. Southerly winds will blow 15-25 mph at mid elevations with gusts to 65-75 mph by afternoon.
Higher elevations will be windy with average winds speeds around 40 mph and gusts to 80 mph.
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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