THIS AVALANCHE FORECAST EXPIRED ON March 9, 2019 @ 6:59 am
Avalanche Forecast published on March 8, 2019 @ 6:59 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

Wind slab avalanche problems will keep the avalanche danger at MODERATE in near and above treeline terrain today. Human-triggered avalanches large enough to have consequences are possible. 

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.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Slabs of wind drifted snow exist on leeward aspects (NW-N-NE-E-SE) in near and above treeline terrain. Where more new snow has accumulated in the last 24 hours, more fragile wind slabs may exist. In areas where older wind slabs exist, they should be more difficult to trigger. Complex or extreme terrain including couloirs, cliffy areas, unsupported slopes, and steep convex rollovers will be the most suspect. Wind slab avalanches could entrain enough snow to bury, injure, or kill a person. Large cornices also exist along exposed ridgelines.

Identify where problematic wind slabs may exist by looking for cornices above a slope, blowing snow, drifted snow, and other wind created surface textures. These areas will have more avalanche concerns and more variable and challenging snow conditions. On the other hand, areas sheltered from the wind should have fewer avalanche concerns and softer more consistent snow conditions.

recent observations

* Yesterday observations from near Ebbetts Pass, on Luther Pass, and on Donner Summit found wind slabs on wind-loaded slopes with a layer of lower density snow below them. Snowmobile cuts and ski cuts on previously undercut wind-loaded tests slopes caused some shooting cracks or test slope failures. Ski and snowmobile cuts on non-undercut slopes did not produce signs of instability. Other tests and observations indicated that these wind slabs are becoming more difficult to trigger, but some snowpit tests still produced unstable results. 

* Large cornices existed above many wind-loaded slopes.

* Observations and data from sheltered slopes in these areas did not show lingering signs of storm slab instability. 

Weather and CURRENT CONDITIONS
weather summary

Expect light snow showers to continue with snowfall intensity and frequency decreasing today and tonight. Some snow showers may linger into tomorrow. The SW winds should follow a similar trend. The forecast also calls for colder than normal temperatures for the next few days. Mostly cloudy skies and colder temperatures in the forecast for today should limit any potential warming from the strong March sunshine. 

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 15 to 18 deg. F.
Max. temperature in the last 24 hours: 27 to 33 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 35 to 45 mph
Maximum wind gust in the last 24 hours: 109 mph
New snowfall in the last 24 hours: 2 to 8 inches
Total snow depth: 120 to 135 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 45%. Mostly cloudy. Slight chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 20%. Partly cloudy then becoming mostly cloudy. Chance of snow showers through the day. Snow levels below 7000 feet. Chance of precipitation is 30%.
Temperatures: 25 to 30 deg. F. 10 to 16 deg. F. 26 to 31 deg. F.
Mid Slope Winds: Southwest 15 to 25 mph with gusts to 45 mph. Southwest 15 to 25 mph. Gusts up to 45 mph decreasing to 30 mph after midnight. Southwest around 15 mph with gusts to 30 mph.
Expected snowfall: 90% probability up to 2 inches. 10% probability of 2 to 3 inches. | SWE = less than 0.10 inch. 90% probability up to 1 inch. 10% probability of 1 to 2 inches. | SWE = less than 0.10 inch. 30% probability up to 1 inch. 70% probability of now accumulation. | SWE = less than 0.10 inch.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 45%. Mostly cloudy. Slight chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 20%. Partly cloudy then becoming mostly cloudy. Chance of snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 30%.
Temperatures: 20 to 26 deg. F. 7 to 12 deg. F. 21 to 27 deg. F.
Ridge Top Winds: Southwest 15 to 30 mph with gusts to 50 mph. Southwest 15 to 30 mph with gusts to 50 mph. Southwest 15 to 25 mph with gusts to 45 mph.
Expected snowfall: 90% probability up to 2 inches. 10% probability of 2 to 4 inches. | SWE = less than 0.10 inch. 90% probability up to 1 inch. 10% probability of 1 to 2 inches. | SWE = less than 0.10 inch. 30% probability up to 1 inch. 70% probability of no accumulation. | SWE = less than 0.10 inch.
Disclaimer

This avalanche forecast is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This forecast 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 forecast applies only to backcountry areas outside established ski area boundaries. This forecast describes general avalanche conditions and local variations always occur. This forecast expires 24 hours after the posted time unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the avalanche forecast call (530) 587-3558 x258