Avalanche Advisory: Saturday - Feb 3, 2018

THIS AVALANCHE ADVISORY EXPIRED ON February 4, 2018 @ 6:51 am
Avalanche Advisory published on February 3, 2018 @ 6:51 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

Avalanche danger is rated LOW today.  Unseasonably very warm temperatures, light winds, and clear skies will make it possible for small loose wet avalanches to occur today on E to S to W facing slopes as they warm from sun exposure.  Firm snow surfaces and obstacles due to the thin snowpack are more of a concern than avalanches at the moment. 

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: Loose Wet
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
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    Very Large
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    Small

Unseasonably very warm temperatures, light winds, and clear skies will make it possible for small loose wet avalanches to occur today on E to S to W facing slopes as they warm from sun exposure.  These are most likely to originate naturally near rock-bands on slopes steeper than 35 degrees, as they heat up from sun exposure and warm up the nearby snow.  Human triggers could also occur as wetness deepens through the snowpack and ski/board penetration becomes deep, and a turn pushes enough snow down slope that could entrain more snow.  While resulting avalanches are not likely to be big enough to bury a person, the heavy thick nature of these slides could drag a person off their feet.  Time it so that you are on steep slopes when they are soft enough for fun turns, and off of them before they become saturated, unsupportable and potentially unstable.   

advisory discussion

Over a week has gone by now since we have had any notable snow deposition from either snowfall or wind transport, and almost as many days of well-above average temperatures.  Despite barely freezing temperatures at night, clear skies will lead to a solid re-freeze of most slopes, before sun exposure tomorrow starts the melt part of the cycle all over again on E-S-W facing slopes at all elevations, and north facing slopes at lower elevations and up to ~9,700’ where slopes are treed.  The only thing different about this early February snowpack warming and the warming that occurs in April is the still-relatively low sun angle in the sky, keeping the intensity of the sun less, and therefore slope warming less.  If we had the same temperatures, winds, and cloud cover in April as we do now, we would expect to see quite a bit more loose-wet activity, and the danger of larger and more numerous slides would be greater.  Still, isolated loose-wet activity is possible, and this should be kept in consideration especially if riding in areas where a small slide could result in a fall in dangerous terrain.  Keep in mind that before these E-S-W facing slopes get exposed to the sun, they are likely to be very firm and icy, and a fall could lead to a slide for life.  Crampons and an ice ax would be wise if it is possible that you might be traveling on these slopes before they soften. 

Persistent loose sugary snow is still being found mid-snowpack in many areas on NE-N-NW aspects due to the thin snowpack.  There have been no reports of any avalanche activity on these layers yet this season, but the weak structure is still important to note, as the possibility, however unlikley, cannot be ruled out.  If we ever get a big heavy dump this season, we wouldn't be suprised to see failures in these deeper layers.  

Lastly, thin snowpack in many areas are hiding rocks, logs, and other obstacles just below the surface.  A skier hit a shallow rock just below the surface that he didn’t see a few days ago skiing out of the negatives, resulting in a fall into other just barely covered rocks, and a broken clavicle. 

Weather and CURRENT CONDITIONS
weather summary

Well above average seasonal temperatures with highs in the upper 40’s around 10,000’, light northerly winds, and sunny skies are expected for today (Saturday).  Winds are expected to pick up Sunday night into Monday as the result of a storm pushing thru the Northwest.

High pressure, dry conditions, and well above average temperatures will be with us thru next week, and who knows how much longer past that.   

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 Clear Sunny then becoming partly cloudy
Temperatures: 50 to 55 deg. F. 28 to 34 deg. F. 49 to 55 deg. F.
Wind Direction: Light Light Light
Wind Speed: Light Light Light
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Saturday Saturday Night Sunday
Weather: Sunny Clear Sunny then becoming partly cloudy
Temperatures: 44 to 49 deg. F. 27 to 33 deg. F. 42 to 48 deg. F.
Wind Direction: North North West
Wind Speed: around 10 mph 10 to 15 mph in the evening becoming light around 10 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 Snowpack Summary is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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