Eastern Sierra Avalanche Advisory

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Avalanche Advisory published on March 1, 2017 @ 6:25 am
This Avalanche Advisory expires in 1 day, 20 hours, 24 minutes
This advisory is valid for 48 hours
Issued by Clancy Nelson - Eastern Sierra Avalanche Center
bottom line

Wind slabs will remain the primary avalanche concern for Wednesday. Though unlikely, it will not be out of the question for a backcountry traveler to trigger these recently deposited slabs on isolated terrain features at mid and upper elevations today. Loose wet avalanches will also become a problem around rocks and on steep slopes at lower and middle elevations. Natural avalanches will be unlikely, human triggered avalanches will be possible. Watch for unstable snow on isolated features such as around rock outcrops and on the leeward side of ridges.

For Thursday, as temperatures rise at all elevations, so will the concern for loose wet avalanches. Heightened avalanche conditions will exist near specific terrain features such as rock outcrops and cliff bands, and on steep slopes where solar radiation is the most intense. There will most likely be small point releases in specific areas and maybe large avalanches in isolated areas. Evaluate snow and terrain carefully.

How to read the advisory

Bottom Line

Wind slabs will remain the primary avalanche concern for Wednesday. Though unlikely, it will not be out of the question for a backcountry traveler to trigger these recently deposited slabs on isolated terrain features at mid and upper elevations today. Loose wet avalanches will also become a problem around rocks and on steep slopes at lower and middle elevations. Natural avalanches will be unlikely, human triggered avalanches will be possible. Watch for unstable snow on isolated features such as around rock outcrops and on the leeward side of ridges.

For Thursday, as temperatures rise at all elevations, so will the concern for loose wet avalanches. Heightened avalanche conditions will exist near specific terrain features such as rock outcrops and cliff bands, and on steep slopes where solar radiation is the most intense. There will most likely be small point releases in specific areas and maybe large avalanches in isolated areas. Evaluate snow and terrain carefully.

Avalanche Problem 1: Wind Slab
  • Character ?
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    Very Likely
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  • Size ?
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  • Trend ?
    Decreasing Danger

Several days of SW winds and a few inches of new snow, primarily around the Mammoth and June areas, have left some isolated wind slabs at mid and upper elevations. Though unlikely to be sensitive or destructive be aware of the potential for these slabs lingering below high elevation ridges and on steep, cross loaded slopes on Wednesday.

Avalanche Problem 2: Loose Wet
  • Character ?
  • Aspect/Elevation ?
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    Certain
    Very Likely
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  • Size ?
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  • Trend ?
    Increasing Danger

Loose cold snow that has been fun to ski will get its first warming as high pressure sets in over the area today. This will create favorable conditions for loose wet avalanches, especially at lower and mid elevations. While most of these point releases will likely be small, some may have the potential to grow to a more threatening size. Wet moving snow is heavy and could knock you off balance or carry you into dangerous terrain. Look for pinwheels rolling down the hill around you as one of the first signs that slopes are warming and becoming unstable.

On Thursday temperatures will rise to well above freezing over the whole forecast area, possibly even at upper elevations. Any slopes that have not yet been warmed will most likely see increased chances of loose wet avalanches. As the snow surface warms quickly, especially around rock outcrops, below cliff bands, and in open bowls throughout the day, loose wet avalanches will be a problem. Time of day is critical with east aspects receiving the first radiation of the day, then south, then west in the late afternoon.

advisory discussion

Continuous winds and cold temperatures ushered in a weak disturbance on Monday. Snowfall totals ranged from 1-7” through the region, with the greatest amounts in the Mammoth and June areas. Steady moderate winds from the southwest had an easy time of redistributing cold and soft snow onto leeward slopes through Tuesday. Wind affected snow surfaces were widely observed. Mammoth Mountain Ski Patrol reported many small soft wind slabs releasing during control work on Monday, but fewer when they reached the upper mountain yesterday morning. Given a short amount of time to adjust, the snowpack seems to be adapting to the load and strengthening. But don’t rule isolated wind slabs out of your hazard and terrain evaluation just yet. Hollow sounding slabs on leeward slopes may still be triggered by a rider’s weight.

And finally, those cold winds have given way to one of the first extended high pressure systems of the season. While it’s far from the tropical vacation that East Side residents dreamed of during the endless stream of Atmospheric Rivers that swept over us earlier this month, temperatures will be above average and winds calm through Thursday. But don’t forget what intense warming will do to the top of the snowpack and the rock outcrops that surround your favorite backcountry chutes and bowls. When unconsolidated snow is newly warmed loose wet avalanches will become a problem. Fortunately the nights will be cold and help keep the melting in check, but as temperatures rise throughout the day be on the lookout. Western slopes will receive more radiation than they have so far this season, now that the sun is getting higher in the sky, and we may see some wet slides on those aspects for the first time. Enjoy the mid winter sun, but don’t ignore obvious signs of instability. Look for roller balls releasing from under cliff bands and on steep solar slopes. Even small point releases are good indicators that slopes are becoming unstable and that larger avalanches may be possible. These smaller slides can knock you off balance and can carry you into dangerous terrain if you aren’t careful.

weather

High pressure will bring dry conditions, light winds, and a slow warming trend through Thursday. Cloud cover will be limited with light winds. Temperatures today will warm up a few degrees with highs around 40 at lower elevations and the upper 30s on the peaks. Chilly nights are expected tonight and Thursday. By Thursday and Friday, most lower elevations can expect highs in the mid 40s. Highs will be near 40 at upper elevations. Friday the ridge becomes flatter, then shifts to the east ahead of the next storm system arriving this weekend.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
  Today Tonight Thursday
Weather: Sunny Clear Sunny
Temperatures: 37-42 deg. F. 9-19 deg. F. 41-46 deg. F.
Wind direction: Var Var Var
Wind speed: Light Light Light
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
  Today Tonight Thursday
Weather: Sunny Clear Sunny
Temperatures: 32-38 deg. F. 11-19 deg. F. 35-41 deg. F.
Wind direction: NW Var Var
Wind speed: 10-15 in the morning becoming light Light Light
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer
This Avalanche Advisory is designed to generally describe avalanche conditions where local variations always occur. This product only applies to backcountry areas located outside established ski area boundaries. 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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