Avalanche Advisory: Monday - Dec 16, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 17, 2019 @ 6:46 am
Avalanche Advisory published on December 16, 2019 @ 6:46 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

MODERATE avalanche danger exists at mid to upper elevations on all aspects with LOW avalanche danger at lower elevations. Fresh Wind Slab will be the primary concern on specific terrain features where strong winds from all directions combined with recent snowfall (6-8”) will load a variety of aspects.

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
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    Possible
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    Very Large
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Expect fresh wind slabs primarily on northerly and easterly aspects with additional wind slab development occurring on sunny aspects (W-S) with current northerly-easterly winds. There is plenty of low density snow ready to be harvested by transporting winds and redistributed to other locations. In most areas below 11000ft, these fresh wind slabs will have been deposited on a Rain Crust laid down during the beginning of the storm Thursday-Friday. (See 12/15 Mammoth Crest Observation). This rain crust may be from 6" to a foot deep from the snow surface and could potentially provide a sliding surface for building wind slabs. Pay attention to tell-tale signs of unstable surface conditions such as active wind loading and shooting cracks.

advisory discussion

Approach the backcountry with focused attention on wise terrain choices for both up and down routes this week.  With Monday’s forecasted sunny skies and access opening up, conditions will present the opportunity for folks to explore higher elevations of the zone. Be on the lookout for clues such as recent avalanches, blowing snow, recent cornice growth, and fat, pillowed snow surfaces. All these clues can help you identify and steer clear of recent fresh wind deposits and potential wind slab or new snow avalanche conditions. Evaluate terrain features that are conducive to capturing drifting snow such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.  Extreme terrain features such as steep couloirs and rolling convexities may present the most hazard for wind slab instabilities or loose snow sloughing right now.

Don’t lose sight that it’s still early and there are a lot of submerged obstacles and hazards out there.

recent observations
Submit Snowpack Observations
Submit Avalanche Observations

12/15 -Mammoth Area –Mammoth Crest – Rain Crust & Surface Hoar Layer

12/15 - Virginia Lakes – South Peak – Northerly winds, wind slab development

12/15 - Rock Creek Area–Snow Conditions

12/14 - Mammoth Area – Sherwins - Snow Conditions/Rain Crust

Weather and CURRENT CONDITIONS
weather summary

A sunny, clear day is on tap with light to moderate easterly winds with 40mph ridge top gusts that are expected to gradually taper in the afternoon. Last night was chilly with single digits throughout the forecast zone, and crisp temperatures will persist on Monday (highs in the teens and low 20s). Another cold night is expected tonight with cloudier conditions returning Tuesday afternoon as a weak upper disturbance works its way into the area. Light snow showers are expected for the Sierra on Wednesday.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Monday Monday Night Tuesday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Partly cloudy then becoming mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 25 to 31. deg. F. 11 to 19. deg. F. 28 to 33. deg. F.
Mid Slope Winds: East to southeast up to 10 mph. Light winds. Light winds becoming southeast around 15 mph with gusts to 30 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Partly cloudy then becoming mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 19 to 25. deg. F. 14 to 20. deg. F. 24 to 30. deg. F.
Ridge Top Winds: Northeast to east 15 to 25 mph with gusts to 40 mph decreasing to 10 to 20 mph in the afternoon. East to southeast around 15 mph becoming south after midnight. South 15 to 25 mph. Gusts up to 40 mph in the afternoon.
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 Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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