THIS AVALANCHE FORECAST EXPIRED ON March 20, 2018 @ 6:58 am
Avalanche Forecast published on March 19, 2018 @ 6:58 am
Issued by Brandon Schwartz - Tahoe National Forest

MODERATE avalanche danger continues today for all elevations. Loose wet avalanches may occur. An unexpected deep slab avalanche was remotely skier triggered yesterday leading to a high degree of uncertainty. Strive to create larger than normal margins of safety while traveling in or below avalanche terrain today.

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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Another round of rapid warming is expected today. Surface wet snow formation will occur with the continued possibility of loose wet avalanches. Loose wet instability is most likely on E-SE-S-SW-W aspects today. Loose wet avalanches may occur on NW-N-NE aspects as well, especially at the mid and lower elevations. Avalanche size is expected to range from very small up to large enough to bury or injure a person (up to size D2).

Natural and human triggered roller balls are an early sign of developing wet snow instability. Avoid travel on steep slopes in areas where roller balls are occurring.

Avalanche Problem 2: Deep Slab
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Inclusion of this problem today is based entirely on the unexpected remotely triggered deep slab avalanche that occurred yesterday on Mt. Houghton (Mount Rose area). There are a significant number of unknowns about this avalanche, leading to a high degree of uncertainly in regards to the problematic weak layer, aspect distribution, and elevation distribution of this problem. Avalanche size up to D3 is possible (large enough to bury and destroy a car, damage a truck, destroy a wood frame house, or break a few trees).

This is a very difficult avalanche problem to manage in the field. Triggering is often much less predictable than the locally more common wind slab and storm slab avalanches. Human triggering may occur above, below, or off to the side of the slope. Deep slab avalanches frequently occur on slopes covered in previous tracks. The only realistic way to manage this problem is through avoidance. Use measured slope angles and/or specific aspect or terrain avoidance to create a larger than normal margin of safety.

recent observations
Submit Observations

* A deep slab avalanche with a crown height estimated at 4 feet was remotely skier triggered yesterday on Mt. Houghton on an E to ENE aspect at approx 10,200'. The party triggered a large collapse just below the ridgetop. Investigation down slope revealed the avalanche crown below a cliff band. The failing weak layer is unconfirmed. An interface at a crust at the base of the recent storm snow is a possibility but uncertain.

* One small human triggered wind slab was reported yesterday from the start zone on the main avalanche path on the ENE aspect of Incline Lake Peak (Mount Rose area).

* Rapid warming conditions were observed yesterday with surface wet snow formation observed on E-SE-S-SW-W aspects. SE-S-SW aspects were effected up into the 9,500' to 10,000' range.

* Three storm slab avalanches likely having occurred on Saturday were noted yesterday in various locations around the Mount Rose area. Two were human triggered and one was a natural. All three were noted to have occurred in the 9,000' to 9,600' elevation range on open E to ESE aspects and well below the ridgetops.

Weather and CURRENT CONDITIONS
weather summary

Expect high level cloud cover, light winds, and above freezing air temperatures today. Cloud cover and precipitation in the form of light rain and snow will spread across the forecast area Tuesday, mainly during the afternoon hours. An powerful atmospheric river type storm system is forecast for the Wed-Fri time period. For more info on this storm check with NWS Reno.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 15 to 23 deg. F.
Max. temperature: 32 to 38 deg. F.
Average ridgetop wind direction: S
Average ridgetop wind speed: 4 mph
Maximum ridgetop wind gust: 15 mph
New snowfall: 0 inches
Total snow depth: 74 to 104 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy skies, becoming partly cloudy. Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies. A chance of snow through the day. Snow level rising to 6,500' in the afternoon.
Temperatures: 38 to 48 deg. F. 22 to 27 deg. F. 39 to 45 deg. F.
Mid Slope Winds: S S S
Wind Speed: Light winds Light winds Light winds
Expected snowfall: 0 0 Up to 1
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy skies, becoming partly cloudy. Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies. A chance of snow through the day.
Temperatures: 32 to 40 deg. F. 22 to 27 deg. F. 35 to 41 deg. F.
Ridge Top Winds: S S S
Wind Speed: 10 to 15 mph with gusts to 25 mph. 20 to 30 mph with gusts to 50 mph. 15 to 25 mph. Gusts to 50 mph decreasing to 40 mph in the afternoon.
Expected snowfall: 0 0 Up to 2
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