Avalanche Advisory: Thursday - Jan 23, 2020

THIS AVALANCHE ADVISORY EXPIRED ON January 24, 2020 @ 6:45 am
Avalanche Advisory published on January 23, 2020 @ 6:45 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

LOW avalanche danger exists at all elevations.  Continue to use safe travel protocols and be on the lookout for small isolated windslabs that could be sensitive to a human trigger in extreme terrain above treeline.  

 

1. Low

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Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Wind Slab
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  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Above treeline in extreme terrain small isolated windslabs remain a concern mainly due to the possibility of knocking a rider off their feet and leading to a bad fall.  Moderate winds shifted out of the north yesterday, and otherwise have been mostly out of the southwest to west since the last snowfall last Thursday. Light winds are expected today with ridge top gusts only into the 20mph range out of the west and southwest, meaning new wind deposition is unlikely today.  Small wind deposits from previous days will vary in sensitivity. Use surface clues to help identify these dense deposits on the leeward side of ridges and sidewalls of gullies, and think about the consequences if a chunk plates out.  Firm conditions will make a small fall in steep terrain hard to arrest.   

 
advisory discussion

Thoughts on our warming conditions:

With the warmest temperatures we've seen in a while expected to reach near 40°F around 10,000’ today, sunny skies at least in the morning, and light winds, small shallow loose wet surface sloughs may result from turns on steep sunny aspects as they warm.  This isn’t listed as a significant problem today however for several reasons: 1) The clear skies last night led to a solid refreeze. 2) Snow on sunny aspects for the most part has already gone thru the melt-freeze transition. 3) The amount of snow on sunny aspects at the warmer lower elevations is quite limited.  None-the-less, keep your eyes out and let us know if you seen anything concerning.  Today’s forecasted weather would be much more concerning if it was following a recent snow storm.                

 

Thoughts on our weak underlying snowpack structure:  

6-12” of new snow fell with extreme winds last Thursday.  Over two weeks of cold clear weather preceded this snowfall which led to a great deal of faceting and weakening of our snowpack in many areas.  While test pits across our range have shown a concerning structure with layers of loose snow under stronger snow, no avalanche activity has occurred since the storm a week ago, and the avalanche activity that was reported during the storm did not involve these buried layers.  Had the latest storm been more significant, these layers most likely would have become reactive and we would have seen many more larger avalanches.  But the amount of new snow we received just wasn’t enough to tip the balance.  Since the storm relatively warm temperatures and extended periods of cloud cover have led to a strengthening snowpack.  None-the-less, our shallow snowpack structure should be kept in mind and continue to be monitored.  Variability is great across our huge forecast area, and it remains important to take your shovel out and do your own localized assessments.  Always use safe travel protocols such as exposing one person at a time.    

 
Weather and CURRENT CONDITIONS
weather summary

Clear and sunny skies are expected this morning, with increasing clouds in the afternoon.  Winds should be light overall with ridge top gusts into the 20s out of the west and southwest, with high temperatures reaching near 40°F around 10,000’. 

 

Dry weather will continue until this weekend when we might see a few inches of snow Saturday night thru Sunday morning, but predicted chances and amounts are dropping as it looks that this incoming storm will stay mostly north of us. 

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 then becoming mostly cloudy. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 5%. Mostly cloudy. Isolated snow showers. Snow levels 8000 feet. Chance of precipitation is 15%. Partly cloudy. Snow levels 7000 feet. Chance of precipitation is 5%.
Temperatures: 39 to 47. deg. F. 25 to 30. deg. F. 36 to 44. deg. F.
Mid Slope Winds: Light winds. Light winds becoming southwest around 15 mph with gusts to 35 mph after midnight. Southwest around 15 mph with gusts to 40 mph.
Expected snowfall: 0 in. up to 1 inch. | SWE = less than 0.10 inch. in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Sunny then becoming mostly cloudy. Snow levels below 7000 feet increasing to 7500 feet in the afternoon. Chance of precipitation is 5%. Mostly cloudy. Isolated snow showers after midnight. Snow levels 8000 feet. Chance of precipitation is 20%. Partly cloudy. Snow levels 7500 feet. Chance of precipitation is 10%.
Temperatures: 32 to 40. deg. F. 20 to 25. deg. F. 29 to 37. deg. F.
Ridge Top Winds: West around 15 mph. Gusts up to 25 mph in the afternoon. Southwest 15 to 25 mph. Gusts up to 25 mph increasing to 40 mph after midnight. Southwest 15 to 30 mph with gusts to 50 mph.
Expected snowfall: 0 in. up to 1 inch. | SWE = less than 0.10 inch. 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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