Avalanche Advisory: Thursday - Feb 4, 2021

THIS AVALANCHE ADVISORY EXPIRED ON February 5, 2021 @ 6:58 am
Avalanche Advisory published on February 4, 2021 @ 6:58 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

MODERATE Avalanche Danger exists today for Wind Slab and Cornice problems from recent violent SW winds. Northerly-Easterly aspects and complex terrain prone to capturing wind transported snow should be evaluated carefully at all elevations. Remain cognizant of the potential for Persistent Slab issues deeper in the snowpack.

Thank you to everyone who was able to make it to our second virtual education event focusing on Avalanche awareness, How to use the advisory, and a discussion about the current state of the snowpack. This event was recorded and is available to view on our YouTube page!

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.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    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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Northerly-Easterly aspect slopes adjacent to and underneath ridgelines and cliff features will be of most concern for finding wind slab Thursday. The wind storm yesterday was almost too extreme to really load a lot of slopes, but these violent winds can alternatively load slopes dynamically and in areas mid slope and lower. With limited observations up high, our advice is to remain vigilant for fat looking pillows, cross-loaded gullies and convexities. Shifting light to moderate North winds in the upper elevations may also move a bit of snow back to Southerly aspects in the alpine. Take note of warming temperatures and a bright sunny day that could loosen small panels of wind deposited snow which may impact you from above if traveling up colouirs or tight constricted terrain. Be aware that triggering a larger wind slab may result in enough weight to trigger a Persistent slab avalanche in weak basal snow.

Avalanche Problem 2: Persistent Slab
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The bottom line is that we now have a robust slab nearly 3-4ft deep in a majority of northerly-easterly terrain focused in the Mammoth area to the north. This beefy slab is resting on a shallow and loose-grained snowpack from November and December. This issue is of most concern on N-E aspects, but we are not ruling out the broader aspect range of W-SE aspects due to patchy remnant old snow coverage. This issue likely contributed to a large Skier-triggered avalanche in Punta Bardini this past Saturday. Areas of particular concern are steep (>30deg) unsupported slopes, and areas with lots of rock and cliffs that harbor cavities and weaker more faceted basal depth hoar and loose grained snow.

Avalanche Problem 3: Cornice
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Identify and avoid newly built cornices on NW-SE ridgelines Thursday. Cornice failures and subsequent wind slab avalanches were observed throughout the Mammoth area the past few days. Give these wave-like features adjacent to ridgeline a wide margin while traveling on top of ridges and avoid being underneath them. Warming temperatures and a bright sunny day may loosen fresh hanging deposits of snow.

Weather and CURRENT CONDITIONS
weather summary

After yesterday’s wind event, things settled down last night and should be fairly tranquil comparatively today. Northerly winds of 15-25mph with gusts to 35 are on tap for ridge top today. Temperatures will be around freezing and sunny conditions will prevail. It looks like we settle in to high pressure, sun and no precipitation again for a while with low chances of weak systems next week.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Thursday Thursday Night Friday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 30 to 36. deg. F. 18 to 23. deg. F. 36 to 44. deg. F.
Mid Slope Winds: Light winds. Light winds. Northwest around 15 mph with gusts to 30 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 26 to 32. deg. F. 15 to 20. deg. F. 30 to 36. deg. F.
Ridge Top Winds: North 15 to 25 mph with gusts to 35 mph. Northwest 15 to 25 mph with gusts to 40 mph. Northwest 20 to 35 mph with gusts to 55 mph.
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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