Avalanche Advisory: Wednesday - Jan 27, 2021

THIS AVALANCHE ADVISORY EXPIRED ON January 28, 2021 @ 6:40 am
Avalanche Advisory published on January 27, 2021 @ 6:40 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

Avalanche danger is HIGH today as a powerful winter storm is hitting the Eastern Sierra. Extreme southerly winds with heavy accumulations of new snow will build Slabs on All Aspects. Avoiding all Avalanche terrain is recommended as natural and human triggered avalanches are certain.

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Below Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Extreme southerly winds combined with significant rapid new snowfall will build reactive and deep wind slabs on virtually all aspects and elevations. W-N-E-SE will be aspects of primary concern with gauranteed wind slab development adjacent to ridgeline and terrain features conducive to capturing wind transported snow such as cliff bands, convex roll overs and gully features. Large to very large natural avalanches are likely today and could run into lower terrain where you may normally think you are safe. Again, travel in avalanche terrain and lower elevations potentially affected from above are not recommended right now.

Avalanche Problem 2: Storm Slab
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Multiple feet of new snow are slated to rapidly fall today and will build fresh sensitive slabs on All Aspects at All Elevations. In the midst of a storm of this magnitude avalanche conditions will be very dangerous as new snow will be looking to adjust its balance in relation to gravity and slope. This means avalanches in many forms, from soft sensitive storm slabs to loose dry point releases. It's going to be an active few days in relation to avalanche activity and best to let mother nature do its thing, adjusting and reaching equilibrium on its on terms rather than you testing it.

Avalanche Problem 3: Persistent Slab
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This massive storm will rapidly load the old, weak, shallow and loose-grained snowpack from November and December with a significant amount of weight. NW to E aspects all harbor weak structure from our prolonged drought through the whole first half of the winter. The rapid loading and large amount of weight in the new snow will likely cause collapse and failure in these old weaker layers. Avalanches originating from fresh unstable wind/storm slab and loose dry will add to the pressure on these weak persistent layers and could cause avalanches to “step down” into the older snowpack resulting in much bigger and destructive avalanches.

advisory discussion

This is the storm we have all been waiting anxiously for, but as a wise friend once told me, “Some days are better for making soup.” The point being that when the dust settles and the snow stabilizes there will be plenty of riding for everyone in the near future. Trying to get out in the midst of this maelstrom the next few days may bring more Risk than Reward. The speedy amount of new snow, extreme winds and massive amount of weight added to our weak snowpack are all major red flags. Patience is key!

recent observations
Submit Snowpack Observations
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1/26 – Mammoth Area –Red Cone—new snow and winds

1/26 – June Lk Area – Hourglass & Negatives – Cold temps & Wind slab on NE

1/26 – Mammoth Area – Hemlock Ridge – small loose dry slides

1/26 – Mammoth Area – Lake Basin – snow conditions

Weather and CURRENT CONDITIONS
weather summary

A blizzard warning is in effect until 10am Friday. Significant snowfall accumulations are slated through Thursday night as an impressive storm driving atmospheric river moisture takes aim at the Eastern Sierra. Multiple FEET of snow are expected being driven by extreme southerly winds gusting up to 115mph at times. Temperatures should remain cold with 14-20defgF in the Upper elevations and reaching 26degF below tree line. On the high end liquid amounts could reach over 4” through Thursday with the potential for 80” of snowfall. These are high-end predictions given this morning by the weather service.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 95%.
Temperatures: 20 to 26. deg. F. 18 to 24. deg. F. 22 to 28. deg. F.
Mid Slope Winds: South 25 to 40 mph with gusts to 95 mph decreasing to 20 to 30 mph with gusts to 75 mph in the afternoon. South 15 to 25 mph with gusts to 60 mph. South 15 to 25 mph. Gusts up to 55 mph decreasing to 45 mph in the afternoon.
Expected snowfall: 70% probability of 21 to 29 inches. 30% probability of 12 to 20 inches. | SWE = 1.25-2.25 inches. in. 80% probability of 16 to 24 inches. 20% probability of 10 to 16 inches. | SWE = 1.05-1.55 inches. in. 80% probability of 10 to 18 inches. 20% probability of 15 to 20 inches. | SWE = 0.75-1.25 inches. in.
Over 10,000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 14 to 20. deg. F. 11 to 16. deg. F. 15 to 21. deg. F.
Ridge Top Winds: South 45 to 65 mph with gusts to 115 mph decreasing to 35 to 55 mph with gusts to 95 mph in the afternoon. South 30 to 45 mph with gusts to 75 mph. South 35 to 50 mph decreasing to 20 to 30 mph in the afternoon. Gusts up to 75 mph.
Expected snowfall: 70% probability of 25 to 33 inches. 30% probability of 12 to 20 inches. | SWE = 1.35-2.35 inches. in. 80% probability of 19 to 27 inches. 20% probability of 10 to 18 inches. | SWE = 1.00-2.00 inches. in. 80% probability of 12 to 20 inches. 20% probability of 15 to 20 inches. | SWE = 1.00-1.50 inches. 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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