THIS AVALANCHE FORECAST EXPIRED ON January 18, 2018 @ 6:52 am
Avalanche Forecast published on January 17, 2018 @ 6:52 am
Issued by Steve Reynaud - Tahoe National Forest

Low avalanche danger continues at all elevations throughout the forecast region.  A persistent slab avalanche problem continues to exist in isolated areas in near treeline and below treeline terrain.  Avalanche danger is expected to increase tomorrow as a strong winter storm impacts our 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: Persistent Slab
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

A weak layer of faceted snow continues to persist within the snowpack.  This persistent slab avalanche problem exists on NW-N-NE aspects in below treeline and near treeline terrain.  Snowpack tests continue to show unstable results on this layer at many locations throughout the forecast area.  Although this weak layer has become moist to wet in some locations, it still remains loose and weak.  Triggering this weak layer today will remain unlikely.  Concern exists that this weak layer could become reactive with increased load from the forecasted winter storm on Thursday/Friday. 

Look for collapsing, cracking, or whumpfing sounds.  Be aware that persistent slabs can be remotely triggered and could also fail low to mid slope.  Handpits and ski pole probing remain effective tools to help identify where this persistent weak layer may exist.

recent observations

* Unstable test results reported in near and below treeline terrain on the buried facet layer over the last week:  Elephants Hump (Carson Pass area), Red Lake Peak (Carson Pass area), Slab Cliffs (Mt. Rose area), Tamarack Peak (Mt. Rose area), and Castle Peak (Donner Summit area).  Other locations are showing this layer and the overall snowpack gaining strength.

* 1 natural triggered persistent slab avalanche on Jan. 11 reported.  No human triggered avalanches reported on this weak layer.

* NW-N-NE aspects above 8,000' in the Mt. Rose area and along the Sierra Crest north of Emerald Bay hold the best coverage at 2 to 4+ feet. Overall less snow cover exists south of Emerald Bay. Areas of decent coverage exist above 8,300' on NW-N-NE aspects in the Carson Pass area.  Coverage decreases dramatically on all other aspects.

Weather and CURRENT CONDITIONS
weather summary

Mild weather will continue today with cloudy skies and above average temperatures ahead of an approaching strong winter storm.  Strong to gale force SW winds will develop Thursday morning with heavy snowfall forecasted from Thursday afternoon through early Friday morning.  This storm could bring 1 to 2' of snow to areas above 6500' with snow levels dropping below lake level.  An additional storm is possible for Sunday into Monday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 33 to 39 deg. F.
Max. temperature in the last 24 hours: 42 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 20 to 30 mph
Maximum wind gust in the last 24 hours: 38 mph
New snowfall in the last 24 hours: 0 to 2 inches
Total snow depth: 21 to 38 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy. Mostly cloudy. Mostly cloudy. Chance of rain and snow through the day.
Temperatures: 47 to 52 deg. F. 33 to 38 deg. F. 42 to 47 deg. F.
Winds: SW SW SW
Expected snowfall: 0 in. 0 in. Up to 3 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy. Mostly cloudy. Mostly cloudy. Chance of snow through the day. Chance of rain in the afternoon.
Temperatures: 44 to 49 deg. F. 31 to 36 deg. F. 38 to 44 deg. F.
Winds: SW SW SW
Expected snowfall: 0 in. 0 in. Likely up to 3 in. | Possible 2 to 6 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This advisory covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258