Fresh new windslabs have formed as a result of new snowfall late yesterday afternoon and evening accompanied by very high winds out of the southwest. 2” - 10” of new snow has fallen since yesterday afternoon, once again with the greatest amounts being recorded around the Mammoth area, and significantly less both north and south. High winds at mid to upper elevations, blowing near 80mph over ridgetops, have formed fresh sensitive windslabs that are most likely to be found just below ridgetops, on the sidewalls of gullies, and across cross-loaded slopes that face NW-N-NE-E-SE. These windslabs will continue to form and be sensitive throughout the day today as moderate winds out of the southwest continue to transport snow. Natural avalanches could be possible, and human triggered avalanches likely on exposed slopes greater than 35 degrees, especially at mid to upper elevations. As snowfall begins once again and winds increase during the day on Sunday, this avalanche concern will become even greater. The size and consequence of these avalanches will be greater for areas in the region that received greater amounts of new snow, but realize that even small avalanches in steep terrain where obstacles or terrain traps are present can results in injury or death.
Storm slabs that could be sensitive to human triggering may be found on all aspects in wind-protected areas, especially where snowfall amounts were greater than 6”. Prior to this last snowfall, many mid and low elevation slopes, along with upper elevation slopes that have had sun-exposure (non-northerly aspects) have developed smooth melt-freeze crusts. On more northerly facing slopes at mid to upper elevations, smooth surfaces exist in many areas in the form of windcrusts. These various smooth snow surfaces that existed prior to this recent snow fall will make for good sliding surfaces for this new snow to fail and avalanche on. The concern over storm-slab instability will begin to diminish as they are given time to settle towards the end of the day today and into tomorrow morning, but will again become heightened as new snowfall begins during the day on Sunday,
In exposed, high elevation terrain (>11,500') that faces N to NE some areas of very faceted shallow snowpacks have been found to exist prior to last weekend's storm. It is likely that some of these weak areas avalanched naturally during this past storm, and it is also likely that some still exist that are now covered with windslab. This underlying weak faceted layer wont stabilize quickly. While a stiff thick overlying windslab may bridge over this weak layer effectively at many points, it is very possible that a human could trigger a failure where the slab is thinner. It is possilbe that such a failure could propagate above the trigger and result in a dangerous avalanche that a human would have a hard time getting out of. Be aware and on the lookout for this potential problem if you find yourself in this kind of high elevation terrain.
Heightened avalanche concern exists today in the form of fresh new windslabs that have formed as a result of new snowfall late yesterday afternoon and evening accompanied by very high winds out of the southwest. 2” - 10” of new snow has fallen since yesterday afternoon, once again with the greatest amounts being recorded around the Mammoth area, and significantly less both north and south. High winds at mid to upper elevations, blowing near 80mph over ridgetops, have formed fresh sensitive windslabs that are most likely to be found just below ridgetops, on the sidewalls of gullies, and across cross-loaded slopes that face NW-N-NE-E-SE. These windslabs will continue to form and be sensitive throughout the day today as moderate winds out of the southwest continue to transport snow. Natural avalanches could be possible, and human triggered avalanches likely on exposed slopes greater than 35 degrees, especially at mid to upper elevations. As snowfall begins once again and winds increase during the day on Sunday, this avalanche concern will become even greater. The size and consequence of these avalanches will be greater for areas in the region that received greater amounts of new snow, but realize that even small avalanches in steep terrain where obstacles or terrain traps are present can results in injury or death.
There is also some avalanche concern over storm slabs that could be sensitive to human triggering on all aspects in wind-protected areas, especially where snowfall amounts were greater than 6”. Prior to this last snowfall, many mid and low elevation slopes, along with upper elevation slopes that have had sun-exposure (non-northerly aspects) have developed smooth melt-freeze crusts. On more northerly facing slopes at mid to upper elevations, smooth surfaces exist in many areas in the form of windcrusts. These various smooth snow surfaces that existed prior to this recent snow fall will make for good sliding surfaces for this new snow to fail and avalanche on. The concern over storm-slab instability will begin to diminish as they are given time to settle towards the end of the day today and into tomorrow morning, but will again become heightened as new snowfall begins during the day on Sunday,
Overnight snowfall from remote weather stations:
VA Lakes Ridge(9443’): 4” new snow / 0.2”H2O
GEM Pass(10750’): 4.5” new snow / 0.3” H2O
June Mtn(9148’): 4” new snow / 0.4” H2O
Mammoth Mtn(9014’): 10” new snow / 1.2” H2O
Mammoth Pass(9500’): 10” new snow / 1.2” H2O
Rock Creek(9800'): 2" new snow
Big Pine Creek(10000'): 2" new snow
Observations made in the Mammoth area, June area and Rock creek over the past several days are showing a mostly stable underlying snowpack with very variable surface conditions including many firm surfaces that are either melt-freeze crusts or wind crusts that could make for good sliding layers for new snowfall to fail on.
We are in the middle of another series of winter storms that are bringing high winds and periods of heavy snowfall to our region. The bulk of the storms will be centered north of our area toward Tahoe and north, however we will still see impacts. Today (Saturday) we are in a break between last night’s storm and the one that is expected to move in during the day on Sunday. Expect mostly cloudy skies, temperatures in the low to upper 30s, and moderate winds out of the southwest at 25-40mph, with 60mph gusts over ridgetops. Tomorrow (Sunday), precipitation will begin as the moisture plume dips south during the day. Higher snow amounts are expected towards the north parts of our region, with potentially 1-1.5ft along the crest. Strong high winds out of the southwest will persist through much of the day in the 40-60mph range, with gusts in the 90s over ridgetops. Temperatures should be several degrees cooler than Saturday.
Snow showers should taper off by early Monday morning, strong winds are expected to continue through the day, and temperatures should be a few degrees warmer.
For Tuesday through the rest of next week, a high-pressure ridge near the coast will keep conditions dry, winds light, and temperatures near or slightly above average.
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This snowpack summary applies only to backcountry areas outside established ski area boundaries. This snowpack summary only describes general avalanche conditions and local variations always occur. This snowpack summary expires 24 hours after the posted time unless otherwise noted. The information in this snowpack summary is provided by the Eastern Sierra Avalanche Center who is solely responsible for its content.
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