THIS AVALANCHE FORECAST EXPIRED ON March 12, 2018 @ 6:57 am
Avalanche Forecast published on March 11, 2018 @ 6:57 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger remains LOW for all elevations. Avalanche activity is unlikely on a regional scale. Isolated areas of unstable snow may exist somewhere within the forecast area. Small and mostly inconsequential loose wet instability may occur today. Deep slab avalanches are very unlikely but not impossible.

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: Normal Caution
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The snowpack is generally stable. Some minor amounts loose wet instability may occur today on any aspect, especially at the mid and lower elevations. In general, areas of loose wet instability are not expected to present much of a hazard to backcountry travelers today. Keep an eye out for fresh roller ball activity as a sign of instability. If in doubt avoid steep slopes where any signs of wet snow instability, either new or old are present.

Triggering a deep slab avalanche is very unlikely on a regional scale but cannot be ruled out entirely. Exercise normal caution such as exposing only one person at a time to avalanche terrain and moving from safe area to safe area. Keep in mind that in the unlikely event that a deep slab avalanche were to occur, avalanche size will be large (D3). Factor large avalanche size into safe area selection and do not rely on marginal quality safe areas. Anticipate potentially long avalanche runouts into treed terrain. If in doubt, increase the margin of safety by choosing less complex terrain and increasing the distance from areas of exposure to potential avalanches.

 

recent observations
Submit Observations

* Snowpit data was collected yesterday at the site of the March 4th Negro Canyon deep slab avalanche (Donner Summit area). Significant rounding of the once faceted layer of concern was observed. Snowpit tests at this location showed a significant increase in stability.

* Snowpit data collected yesterday in two ridgetop locations on Becker Peak (Echo Sumit area) showed a lingering, difficult to trigger potential for deep slab instability.

* Other recent observations from around the forecast area targeting the recent deep slab problem have overall shown signs of increasing stability. General trends in snowpit data are that the once faceted weak layer of concern is located 3 to 6 feet deep in the snowpack, remains significantly less dense than the slab above it, and often presents as loose grains. Varying degrees of rounding of the once faceted snow have be observed. In some locations, faceted crystals are no longer visible under magnification. Snowpit tests indicate that it is difficult to trigger weak layer failure (ECT, CT). Tests specifically examining propagation potential (such as the PST) tend to indicate that propagation could still occur along the weak layer in the unlikely event that snowpack failure is triggered.

* Warm air temperatures and high humidity with snow levels around 6,800' to 7,500' were reported yesterday afternoon. Wet snow surfaces and minor amounts of loose wet instability were reported below 8,000'.

 

Weather and CURRENT CONDITIONS
weather summary

Short lived high pressure is forecast for the region today and Monday. Areas of morning cloud cover are expected to give way to sunny skies by the afternoon. Above freezing maximum daytime air temperatures are forecast for today and tomorrow. Ridgetop winds are expected to remain fairly light today, increasing out of the S to SW on Monday.  A series of storm systems are forecast to impact the region with precipitation starting Tuesday and continuing through the end of the week.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 25 to 30 deg. F.
Max. temperature: 33 to 38 deg. F.
Average ridgetop wind direction: S
Average ridgetop wind speed: 14 mph
Maximum ridgetop wind gust: 35 mph
New snowfall: Trace to 3 inches
Total snow depth: 49 to 83 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy skies. Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies, becoming sunny.
Temperatures: 43 to 48 deg. F. 27 to 32 deg. F. 45 to 50 deg. F.
Mid Slope Winds: SW SE S to SW
Wind Speed: Light winds Light winds Light winds
Expected snowfall: 0 0 0
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy skies. Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies, becoming sunny.
Temperatures: 38 to 44 deg. F. 27 to 32 deg. F. 41 to 47 deg. F.
Ridge Top Winds: SW SE S to SW
Wind Speed: Light winds 10 to 15 mph. Gusts to 25 mph increasing to 35 mph after midnight. 15 to 25 mph with gusts to 45 mph.
Expected snowfall: 0 0 0
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