Eastern Sierra - Sun Jan 10 2010
Eastern Sierra avalanche advisory
Posted January 10, 2010 by Sue Burak
In very isolated areas in extreme terrain, small avalanches are possible. The avalanche danger is LOW on slopes where there is enough snow for an avalanche to occur.
Yesterday morningÂ’'s fog gave way to very mild weather as temperatures climbed into the mid to upper 40's at most mountain locations. Winds were light and westerly, with mid level clouds moving in by mid morning.
Throughout the region, the cloudy weather and mild temperatures produced alot of snowmelt at the 7,000 to 8,000 ft elevations and compaction at higher elevations. Rocks are showing in bowls off the Mammoth Crest where none could be seen at the beginning of the week. The snowpack that is still around is strong, though faceted grains and new snow at the surface could be the weak layer for the next snowfall.
An inch or two of new snow and graupel fell in the Mammoth Lakes Basin Friday. Thin crusts formed below the new snow in some places while sheltered slopes had new snow over near surface facets. I expect recrystallization to occur on shady tree covered slopes until the Tuesday/Wednesday storm arrives. New snow will fall on a variety of weak old snow surfaces and will make for tricky avalanche conditions.
Another anemic weather system brought rain and less than an inch of new snow to the region Friday night and Saturday. The low level air mass is saturated and there is a freezing fog advisory until 10 AM this morning. Lee Vining never completely burned off yesterday.
Dry conditions will continue through Monday, then a wetter system moves into the forecast area later Monday night and early Tuesday morning. The Tuesday/Wednesday storm is expected to split with the storm track favoring southern California and the southern Sierra around Tehachipi and the Grapevine. The northern jet will put northern California in a favored position for snowfall and rain. We are no man's land between the branches of the jet.
The Tues/Wednesday storm will come in with snow levels around 8,000 ft. Rain could fall in Mammoth. By early Wednesday, the front moves in, temperatures will fall and snowlines will lower to 6,000 to 7,000 ft. Total precipitation is forecasted to be close to one inch for elevations above 9,000 ft which could mean a foot of new snow.
Temperatures today will reach the mid 40's at the 8,000 to 10,000 ft elevations. Higher terrain will be only slightly cooler with highs in the mid 30's to around 40.
Winds will be light today then increase Monday afternoon.
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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