Avalanche Advisory: Thursday - Jan 24, 2019

THIS AVALANCHE ADVISORY EXPIRED ON January 25, 2019 @ 7:04 am
Avalanche Advisory published on January 24, 2019 @ 7:04 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

MODERATE avalanche danger remains today due to the uncertainty surrounding an unlikely but not impossible persistent slab avalanche. Other concerns include small loose-wet avalanches on sunny slopes, and old small stubborn wind slabs.  Make terrain choices based on your own local assessments. 

1. Low

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

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: Persistent Slab
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A week has now gone by since heavy loading resulted in widespread avalanche activity occurring on deeper buried layers of weak snow.  Several skier triggered avalanches occurred involving these layers up to 2 days after this storm.  Recent snow pits are still finding various layers of loose weak snow deep in the snow pack, but tests are showing that these layers are becoming less and less reactive.  Still, our zone is large, and it is not inconceivable that some areas may exist where a human could impact a layer of sensitive snow and trigger a slide that could propagate into a large dangerous avalanche.  It is a good idea to take the time and perform your own local assessments by digging down and checking out these potentially concerning layers.  These are likely to be near the ground in areas such as Bishop and Rock Creek, and more mid-pack north of those areas. 

Avalanche Problem 2: Loose Wet
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Sunny skies today and light winds will allow for slopes with exposure to the sun to warm and become less stable.  Watch for loose wet activity on east facing slopes in the morning, followed by south, then west in the afternoon.  Rock outcrops will warm the snow even more.  While these are likely to be small, they could knock a person off their feet and carry them especially in the confines of a couloir.    

Avalanche Problem 3: Wind Slab
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Winds have switched directions over the last several days from SW to W to N to NE.  Winds decreased quite a bit yesterday, and are expected to be light today.  While new wind slabs will be very unlikely, old small stubborn wind slabs with lingering sensitivity could be found in isolated areas and extreme terrain that could knock a rider off their feet and lead to nasty fall. 

advisory discussion

The persistent slab avalanche problem is a tricky one, and our large area and limited number of observations leads to a lower level of confidence than we would like to have in dropping the danger for this problem to LOW.  The deeper buried facet layers are strengthening in areas with deeper snow packs, and reports continue to come in that the buried surface hoar layers are strengthening as well.  While the likelihood is low for an avalanche to be triggered, the size would likely be large and deadly, and it would likely release above the trigger. While variability is great across slopes, likely trigger points are where the snowpack is most shallow.  

recent observations
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-1/23 - Convict – Mini Morrison: Buried surface hoar decomposing, thin recent dense wind slabs on top failing cleanly with hard to mod force in hand pits.

-1/23 – Bishop – Bishop Bowl: Thin snowpack, hollow underneath, warm temps.  

-1/23 – Lee Vining – V-Bowl, Below Dana Plateau: Sun, warmth, small roller balls; strong gusty winds.

-1/23 – Mammoth – Mammoth Crest: Sun and warmth – wet snow, wind-scoured slopes, stubborn wind slab.

-1/22 – Mammoth – Bloody thru the Crest: NE winds transporting snow at upper elevations.

-1/22 – Rock Creek – Red Mtn: Small shooting cracks, easy and clean hand-shear of recent wind deposit. 

 -1/22 – June – Hemlocks: Several facet layers deep in snowpack, un-reactive in tests.

-1/22 – Lee Vining – V-Bowl: Buried surface hoar issue found to be settling out. 

 

Weather and CURRENT CONDITIONS
weather summary

Yesterday was very warm and sunny, with high temperatures reaching 50 degrees at 9500’! Today expect sunshine and warm temperatures again, but not as warm as yesterday.  North winds will be light.  High pressure continues to build thru the weekend, with increasing high temperatures each day.  

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. Clear. Sunny.
Temperatures: 30 to 40. deg. F. 22 to 30 deg. F. 35 to 45. deg. F.
Mid Slope Winds: East winds 10 to 15 mph. Gusts up to 25 mph. East winds around 10 mph with gusts up to 20 mph in the evening. Light winds after midnight. West winds 10 mph becoming northeast 10 to 15 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Thursday Thursday Night Friday
Weather: Sunny. Clear. Sunny.
Temperatures: 28 to 33. deg. F. 18 to 25. deg. F. 31 to 37. deg. F.
Ridge Top Winds: North 10 to 15 mph with gusts to 25 mph. Northeast 10 to 15 mph. Gusts up to 25 mph in the evening. Northwest 15 to 30 mph with gusts to 45 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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