Avalanche Advisory: Friday - Jan 24, 2020

THIS AVALANCHE ADVISORY EXPIRED ON January 25, 2020 @ 6:54 am
Avalanche Advisory published on January 24, 2020 @ 6:54 am
Issued by Steve Mace - ESAC

Low avalanche danger exists at all elevations today. Isolated areas of wind slab on northerly and easterly terrain at upper elevations remain the primary concern. In addition, the overall poor structure of our snowpack deserves extra consideration. Practice safe travel techniques and evaluate terrain carefully.

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
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Southwest winds increased last night with sustained strong winds and gusts over 60mph recorded on the summit of Mammoth mountain. While only limited amounts of loose snow remain available for transport, winds are predicted to remain strong throughout the day today. It will not be impossible to find isolated areas of fresh wind slab development on leeward slopes at upper elevations. Elevated caution is recommended in extreme and complex terrain such as unsupported slopes, cliffy areas, and confined couloirs. Use surface clues such as blowing snow, recent cornice growth, and uneven snow surfaces to identify features of concern.

advisory discussion

It has been tricky this week deciding whether or not to include persistent slab as a problem in our avalanche advisories. Field observations continue to highlight our thin snowpack and poor structure.  Numerous large collapses and test results showing propagation potential have been reported from all corners of the range, and these signs of instability are keeping forecaster confidence low.  While a weak faceted snowpack has been found throughout the range at all elevations, we cannot point to a specific layer of concern. Rather we are dealing with a variety of facet crust combos and large variability when it comes to slab density and thickness.  In isolated high elevation catchment zones, loose facets are underlying a thick, dense wind slab while in many lower elevation areas, we are finding thinner melt-freeze or wind crusts interacting with faceted grains.  It is likely that a large load of new snow would initiate a significant avalanche cycle. However, we have not yet received any reports of avalanche activity on these buried weak layers. Given the extreme variability across the landscape, we cannot discount the possibility of isolated areas where an avalanche could be triggered, but in reality, the risk remains low. It is worth noting that large collapsing has been reported at lower elevations where the underlying snowpack is relatively thin. In these areas, shallowly buried rocks and bushes act as trigger points and may aid in the propagation of a weak layer. In times with high uncertainty and large variability, it is advisable to approach objectives with elevated caution and use terrain choice to limit your exposure.  Don’t be afraid to dig in and evaluate the underlying snowpack for instabilities and realize that many preseason hazards such as shallowly buried rocks and trees punctuate the landscape.

Weather and CURRENT CONDITIONS
weather summary

 Partly cloudy skies and warm temperatures can be expected today with strong winds out of the Southwest.  Highs above freezing are expected at upper elevations today, and ridgetop gusts are expected over 60 mph. 

Models continue to show the potential for unsettled weather later this weekend with light showers and gusty winds expected on Sunday.

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: Partly cloudy. Partly cloudy then becoming mostly cloudy. Mostly cloudy then becoming partly cloudy.
Temperatures: 35 to 43. deg. F. 23 to 28. deg. F. 38 to 46. deg. F.
Mid Slope Winds: Southwest 15 to 25 mph with gusts to 35 mph. West 10 to 20 mph in the evening becoming light. Light winds.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Friday Friday Night Saturday
Weather: Partly cloudy. Partly cloudy then becoming mostly cloudy. Mostly cloudy then becoming partly cloudy.
Temperatures: 27 to 35. deg. F. 18 to 23. deg. F. 31 to 39. deg. F.
Ridge Top Winds: Southwest 25 to 40 mph with gusts to 60 mph. West 15 to 25 mph with gusts to 40 mph. West around 15 mph with gusts to 30 mph in the morning becoming light.
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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