Avalanche Advisory: Sunday - Dec 29, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 30, 2019 @ 6:40 am
Avalanche Advisory published on December 29, 2019 @ 6:40 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

MODERATE avalanche danger exists at Upper and Middle elevations on all Aspects with Winds Slab being of primary concern. LOW avalanche danger continues in wind protected lower elevations. A Skier triggered avalanche occurred yesterday.

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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    Very Likely
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Steep terrain with features conducive to capturing drifting snow will be of concern today for wind slab hazard. As winds shift back to a SW flow after 2 days of prevailing northerlies, all aspects should be looked at critically. Yesterday there was a skier triggered slab in steep NE terrain that although not wide, was reported to have run 1200ft . Look for snow surfaces that could indicate deposition vs. scouring and take note of clues such as active wind loading, shooting cracks, or hollow sounding areas. Be flexible with your route plans in relation to changing conditions.

advisory discussion

Major wind transport took place on Friday the 27th and although northerly aspects at and above tree line continued to be stripped yesterday the amount of airborne snow was noticeably less. Conditions on northerly aspects up high are extremely variable with a mix of scoured surfaces, cross loaded drifts adjacent to rock bands/cliffs, and hardened wind slab. Southerly-westerly aspects got loaded the past few days and although this aspect is not on most skiers run menu, it still should be noted and considered. There were avalanche results on cross loaded westerly aspects with explosive testing following this past storm. The Northern part of the forecast zone from June Lake up to Virginia Lakes should be given extra consideration as local snowfall amounts far exceeded anywhere else laying down an average of ~40cm of low density powder.

Although there is already a respectable snowpack in the Mammoth area and high elevations of the forecast zone, a majority of the area still has limited coverage with most backcountry riders reporting hitting obstacles and recording near misses. We’re off to a great start, so Keep It Real for a long season ahead!

Weather and CURRENT CONDITIONS
weather summary

A weak winter storm is projected to enter the area today bringing cloudy skies, light snow showers and warmer temperatures this afternoon and tonight. Winds died overnight and will switch to a SW flow today with light to moderate speeds with gusts up to 40mph at ridge top. Temperatures will be well above freezing in lower elevations with 20-28F range projected above 1000ft. The mountains could see 1-4” of new snow by Monday morning with a switch back to cooler temps and northerly winds again as the system passes by.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 30%. Cloudy. Snow likely in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 90%. Cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 50%.
Temperatures: 29 to 37. deg. F. 17 to 22. deg. F. 24 to 30. deg. F.
Mid Slope Winds: Southwest 15 to 20 mph with gusts to 40 mph. Southeast around 15 mph. Gusts up to 35 mph decreasing to 25 mph after midnight. Northeast 15 to 20 mph with gusts to 45 mph.
Expected snowfall: Less than 1 inch. | SWE = trace amounts. in. 80% probability of 1 to 4 inches. 20% probability of 4 to 6 inches. | SWE = up to 0.20 inch. in. 50% probability up to 2 inches. 50% probability no accumulation. | SWE = less than 0.10 inch. in.
Over 10,000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 35%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 90%. Cloudy. Chance of snow through the day. Snow levels below 7000 feet. Chance of precipitation is 55%.
Temperatures: 20 to 28. deg. F. 12 to 17. deg. F. 17 to 23. deg. F.
Ridge Top Winds: Southwest 15 to 30 mph with gusts to 40 mph. Southwest 15 to 25 mph shifting to the east after midnight. Gusts up to 35 mph. Northeast 25 to 35 mph with gusts to 50 mph.
Expected snowfall: 80% probability up to 1 inch. 20% probability of 1 to 2 inches. | SWE = less than 0.10 inch. in. 80% probability of 1 to 4 inches. 20% probability of 4 to 8 inches. | SWE = up to 0.20 inch. in. 50% probability 1 to 3 inches. 50% probability no accumulation. | SWE = less than 0.10 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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