Avalanche Advisory: Friday - Jan 4, 2019

THIS AVALANCHE ADVISORY EXPIRED ON January 5, 2019 @ 6:47 am
Avalanche Advisory published on January 4, 2019 @ 6:47 am
Issued by Steve Mace - ESAC

Natural and human triggered avalanches will be unlikely today. Isolated pockets of wind slab will be possible to find at upper elevations, which could still be reactive to human trigger. The biggest hazard remains our thin snowpack; be careful out there early season obstacles exist through out our forecast area.

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

Wind slabs continue to be found at upper elevations on all aspects. Moderate south winds are expected today, however, available snow for transport is lacking and new slab development is unlikely.  There is still potential to find isolated pockets of reactive wind slab at upper elevations where these dense slabs may be sitting on top of weak faceted grains.  Do your own localized assessments to determine how sensitive wind slabs are before committing to steeper, more complex terrain where consequences of a slide may be higher.  When in doubt, stick to more simple, sheltered terrain. 

advisory discussion

Over the last week we have seen moderate to strong winds that have turned exposed terrain into a patchwork of scour and wind deposit.  Typically wind slabs stabilize after a few days, however, due to the poor structure of the underlying snow pack we expect lingering pockets of sensitive slab to remain. Recent observations throughout the forecast area have found dense wind slabs sitting on top of layers of weak facets. The presence of persistent grains is concerning and caution should be taken when traveling in exposed terrain.  Forecaster confidence in the distribution and sensitivity of these wind slabs is low and recent events have reminded us that avalanches can happen even in times of low danger.  Use safe travel protocols and conduct localized assessments before committing to suspect slopes.

Another concern is the weak nature of our snow pack.  The recent stint of clear skies, cold temperatures and thin coverage has contributed to faceting throughout the snow pack at all elevations. Buried crusts have started to break down and as a whole the snowpack has become less cohesive.  It’s worth considering the loose nature of the surface snow in steep terrain where sluffs of loose snow could cause a fall. In addition, widespread surface hoar formation has been reported throughout the forecast area at all elivations over the past couple days. It will be important to track on this layer as the predicted storm approaches.  Particularly pay attention to areas where it has not been broken down by wind or direct sun. While benign on the surface, when buried, surface hoar can become a very fragile, dangerous weak layer.   

recent observations
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Jan 3 Rock Creek Alpine Conditions

Jan 2 Surface hoar in the June Lake area

Dec 30 Avalanche Accident  

Weather and CURRENT CONDITIONS
weather summary

Today will be mostly cloudy with temperatures in the low to mid 30’s above 10,000ft.  Winds will be out of the southwest today at moderate speeds (17-25 mph). Temperatures will drop into the teens this evening while winds are expected to increase tonight with sustained southwest winds approaching 45 mph and gusts expected up to 70 mph.  

Expect to see a change in our weather pattern as winter returns to the area tomorrow. Temperatures are going to be in the low to mid 20’s with strong winds, 35-50 mph expected at upper elevations.  2-6 inches of snow is expected through out the day on Saturday and into Sunday morning.  Winter weather will continue through out the week with Wednesday looking to be our best chance of significant snowfall.

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Friday Friday Night Saturday
Weather: Mostly cloudy. Mostly cloudy then becoming partly cloudy. Partly cloudy then becoming cloudy. Chance of snow in the morning, then snow in the afternoon.
Temperatures: 38 to 44. deg. F. 18 to 24. deg. F. 26 to 32. deg. F.
Mid Slope Winds: Light winds becoming southwest 10 to 15 mph with gusts to 35 mph in the afternoon. Southwest 15 to 25 mph. Gusts up to 45 mph increasing to 55 mph after midnight. South 15 to 30 mph with gusts to 80 mph.
Expected snowfall: None in. None in. 2-6 in.
Over 10,000 ft.
Friday Friday Night Saturday
Weather: Mostly cloudy. Mostly cloudy then becoming partly cloudy. Partly cloudy then becoming cloudy. Chance of snow in the morning, then snow in the afternoon.
Temperatures: 32 to 37. deg. F. 14 to 19. deg. F. 20 to 26. deg. F.
Ridge Top Winds: Southwest 15 to 25 mph. Gusts up to 25 mph increasing to 45 mph in the afternoon. Southwest 25 to 35 mph increasing to 30 to 45 mph after midnight. Gusts up to 70 mph. South 35 to 50 mph with gusts to 100 mph.
Expected snowfall: None in. None in. 3-6 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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