Avalanche Advisory: Saturday - Mar 28, 2020

THIS AVALANCHE ADVISORY EXPIRED ON March 29, 2020 @ 6:44 am
Avalanche Advisory published on March 28, 2020 @ 6:44 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

MODERATE avalanche danger exists above and near treeline Saturday for WIND SLAB on Northerly-Easterly slopes. LOW danger exists below treeline. There have been skier triggered avalanches the past two days on N & E aspects at 9800ft in the Mammoth Lakes Basin. Small natural avalanche activity has also been observed primarily on E aspects. Be heads up for any potential warming or greenhouse effects destabilizing new snow deposits on E-S-SW aspects. Choose terrain wisely to avoid fresh cornice, convex and unsupported slopes, or riding over terrain traps. Human triggered avalanches are possible, so evaluate snow and terrain carefully today.

* Given the current situation, an injury at this time requiring medical attention could result in serious consequences for yourself and others. Limit your risks!  

*To comply with the Inyo County Sheriff’s office request, ESAC’s forecasts and field work is now limited to Mono County.

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
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    Very Large
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The Mammoth area is of most concern where the heaviest accumulation of new snow (12”+) fell this past week with strong W-SW winds. Be on the lookout for Wind Slab on NW-N-NE-E-SE aspects especially adjacent to ridgeline, steep midslope rollovers and rib like features that have convex slopes optimal for capturing snow on the leeward side. Observations the past few days have identified large fresh cornices, cross loaded drifts and pillowed snow adjacent to such features. Shooting cracks, audible whoompfing or panels of firmer wind effected snow resting on top of looser, less cohesive snow are good indicators that wind slab is present. Be observant of overhead hazards, especially fresh cornice lines that may be warming and plan your route accordingly if you’re travelling in terrain where avalanches may impact you from above. Maintain good travel protocols, such as traveling slopes one at a time (both up and down), anchoring up in safe spots, and maintaining good communication and consistent group plans and routes.

advisory discussion

Some pockets of instability were still being discovered yesterday and the intense solar input and light winds contributed to changing most snow surfaces that received solar exposure yesterday. Be aware of ncreasingly variable surface conditions including injury-inducing breakable crust. Upon forecaster investigation the skier triggered slide on the Red cone approach Thursday had slid on an East aspect where the new 40cm of snow had slid on an old melt/freeze crust over a steep rolling convex granite slab in a sheltered zone that sees a lot of sun and warming effects. Yesterday’s triggered wind slab was identified on a heavily loaded north aspect with a steep fetch zone optimal for capturing mid-slope wind transported snow. Both these slides had the potential to partially bury or fully bury someone caught in them. These events remind us to always adhere to fundamental travel protocols, constantly re-evaluating current conditions as maintaining good communication with your group.

This has not been the winter, nor the time right now with all we are dealing with, to risk serious injury by skiing carelessly with our overall thin and obstacle ridden conditions.

It is also important to practice social distancing at all times, from travelling in separate cars going to the trailhead, and keeping at least 6 feet between individuals while skinning and re-grouping. We all need to do our part in preventing the spread of this Corona Virus!  

 

Weather and CURRENT CONDITIONS
weather summary

Mostly cloudy skies, light winds and a chance of snow this afternoon are on tap for today. Temperatures below freezing in the 20sF for the higher elevations while 30-38F will be in store below 10000f. Snow is likely tonight with light accumulations and is slated to continue through Sunday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy. Chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 30%. Cloudy. Snow likely. Snow levels below 7000 feet. Chance of precipitation is 65%. Mostly cloudy. Snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 60%.
Temperatures: 30 to 38. deg. F. 17 to 23. deg. F. 30 to 38. deg. F.
Mid Slope Winds: Light winds. Light winds. Light winds.
Expected snowfall: Up to 1 inch. | SWE = less than 0.10 inch. in. 90% probability up to 2 inches. 10% probability of 2 to 4 inches. | SWE = up to 0.15 inch. in. 80% probability up to 2 inches. 20% probability of 2 to 3 inches. | SWE = up to 0.15 inch. in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy. Chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 35%. Cloudy. Snow likely. Snow levels below 7000 feet. Chance of precipitation is 70%. Mostly cloudy. Snow showers likely. Snow levels below 7000 feet. Chance of precipitation is 65%.
Temperatures: 22 to 29. deg. F. 11 to 16. deg. F. 22 to 29. deg. F.
Ridge Top Winds: Light winds. Light winds. Southwest around 15 mph. Gusts up to 25 mph in the afternoon.
Expected snowfall: Up to 1 inch. | SWE = less than 0.10 inch. in. 80% probability up to 2 inches. 20% probability of 2 to 4 inches. | SWE = up to 0.15 inch. in. 80% probability up to 2 inches. 20% probability of 2 to 3 inches. | SWE = up to 0.15 inch. 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 Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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