Avalanche Advisory: Saturday - Jan 26, 2019

THIS AVALANCHE ADVISORY EXPIRED ON January 27, 2019 @ 7:00 am
Avalanche Advisory published on January 26, 2019 @ 7:00 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Overall LOW avalanche danger today does not mean that avalanches are impossible.    Watch for small isolated fresh wind slabs just below upper elevation ridgelines due to increased NE winds and small loose wet activity on sunny slopes.  Most importantly, let the remote possibility of a large and deadly persistent-slab avalanche remind us to always practice safe travel protocols and limit exposure to one person at a time.     

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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NE ridge-top winds increased yesterday, and will continue at moderate levels thru today.  With limited amounts of loose snow available for transport, small isolated pockets of sensitive fresh wind deposit may be found on the leeward side of upper elevation ridgelines.  Be on the lookout for these on NW-W-S-SE facing slopes. While the resulting avalanche is likely to be small, it could result in a bad fall especially in extreme terrain. The sunny skies this morning could make these small slabs on SE-E facing slopes even more sensitive. 

Avalanche Problem 2: Persistent Slab
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A large deadly persistent slab avalanche is not in the realm of impossibility.  A weak underlying snow pack structure exists in many places throughout the forecast zone.  While there have been no recent reports of signs of instability such as avalanches, shooting cracks, or whoomphing, some tests are continuing to show the possibility of a fracture propagating deep in the snow pack. If this type of avalanche were to be triggerted, it would most likely be in a mid-elevation area with a shallow snow pack.  It is not a bad idea to Investigate for yourself by digging down and checking out these deeper layers for yourself.  

Avalanche Problem 3: Loose Wet
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Sunny skies will continue to make small loose wet activity a possibility.  This will be most concerning on E-SE-S facing aspects before this afternoon, and SW aspects if the forecasted clouds do not materialize. Clouds combined with warm air temperatures could result in some loose wet activity on northerly facing slopes at lower elevations as well.  Roller balls are an indication that larger loose wet sloughs are possible especially in confined terrain such as a couloir. 

advisory discussion

We continue to wrestle with the deep weak layers found in many areas in our forecast zone.  Even though the potential is there for a large and destructive avalanche, the very low likelihood of trigger at this point fits it into the LOW hazard category.  Its important to keep in mind that LOW hazard DOES leave room for avalanches!  LOW doesn't mean you can turn your brain off and wander without a giving a thought.  

We have given less potential for a persistent slab avalanche at upper elevations due to upper elevations tending to have deeper snow depths and more hard deep windslabs. Greater depth leads to lower temperature gradients, which tends faceted grains toward rounding and strengthening.  Thick hard windslabs make it much more difficult to trigger deeper weak layers.  Bear-in-mind though that shallow areas that are more sensitive still exist at upper elevations!        

recent observations
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-1/24 - Convict - Mini Morrison: Basal facets.

-1/24 – Lundy Canyon – Deer Creek Shoulder: Hollow snowpack structure, “loose sugary snow pouring out of the wall near the ground”, non-reactive in tests.

-1/24 – Lee Vining Cyn – Below Dana Plateau: Loose facets still reactive in CT tests, buried surface hoar flattening and becoming less reactive.

-1/24 – Lundy Canyon – Investigation of big human triggered slab avalanche on Jan 18th: Basal snowpack still rotten (reactive in deep tap tests), newer slab on top from 1/20 storm still producing propagating results in ECT tests.

-1/24 – June – Chicken Wing: Weak snow structure, thigh deep boot penetration.

-1/22 – Pine Creek – Mt. Tom:  3 Natural D2 avalanches on N and NE aspects occurred on TUESDAY.

Weather and CURRENT CONDITIONS
weather summary

Partly cloudy skies are expected after a morning of sunshine today, along with continued moderate NE winds at upper elevations.  Temperatures are expected to be about 5°F warmer than yesterday’s, reaching the mid 30s around 10,000’.  For Sunday temperatures are expected to jump close to another 10°F warmer than today.  …and High and Dry for the rest of January. 

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny then becoming partly cloudy. Partly cloudy then becoming mostly cloudy. Partly cloudy.
Temperatures: 42 to 50. deg. F. 24 to 32. deg. F. 50 to 58. deg. F.
Mid Slope Winds: Light winds. Light winds. Light winds.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny then becoming partly cloudy. Partly cloudy then becoming mostly cloudy. Partly cloudy.
Temperatures: 35 to 43. deg. F. 29 to 35. deg. F. 44 to 52. deg. F.
Ridge Top Winds: Northeast 15 to 30 mph. Gusts up to 45 mph decreasing to 35 mph in the afternoon. Light winds becoming west 10 to 15 mph after midnight. Northwest 15 to 20 mph with gusts to 30 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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