THIS AVALANCHE FORECAST EXPIRED ON March 2, 2020 @ 7:02 am
Avalanche Forecast published on March 1, 2020 @ 7:02 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

Shifting winds and new snow mean that fresh slabs of wind drifted snow could exist on almost any exposed slopes today. In more sheltered areas soft slabs of new snow or loose cohesionless new snow may exist. Expect wind slab, storm slab, and loose dry avalanche problems today. CONSIDERABLE avalanche danger exists near and above treeline with MODERATE danger below treeline. 

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Slabs of wind drifted snow could exist on almost any aspect today as a result of both SW and NE winds. At first, fresh wind slabs will be most prominent on NW-N-NE-E-SW aspects. As the wind shifts to the NE and increases, some wind slabs will migrate to the SE-S-SW-W-NW aspects. This wind shift started at the northern end of the forecast area last night and should move south through the forecast area today. Today's wind slabs could measure a few feet in depth and could involve enough snow to bury or injure a person. They may not bond well to the old snow surfaces and the weight of a person recreating on a wind loaded slope could trigger wind slab avalanches today. Some natural wind slab avalanches may also be possible in areas with heavy wind loading today.

Use clues like blowing snow, drifted snow, cornices above a slope, and other wind created textures to identify where wind slabs may exist. This information can help create safety margins that avoid potential wind slabs and lead you to less wind-affected snow.

Avalanche Problem 2: Storm Slab
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Changes in snowfall rates and other conditions during this storm could create weaknesses within the storm snow. In some areas, the new storm snow may not bond well to the old snow surfaces. As a result of either of these weaknesses, soft slabs of storm snow could break loose today on some steep slopes where the new snow has enough cohesion to break as a storm slab. These storm slabs would only involve the new snow but they could still entrain enough snow to be problematic. 

Signs of a storm slab problem include recent avalanches, shooting cracks, or feeling softer layers of snow under more dense layers of snow. Watch out for steep slopes where these clues exist. Lower angle sheltered slopes will provide excellent recreation conditions today. 

Avalanche Problem 3: Loose Dry
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In some cases, the sliding snow may lack cohesion and move as more of a loose dry snow sluff. While these may not entrain as much snow as the other problems mentioned above they could still push a person into a terrain trap or knock a person over. 

recent observations
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* Yesterday observations continued to show a wide variety of snow surfaces. Sun-exposed E-SE-S-SW-W aspects held melt-freeze conditions and NW-N-NE aspects held a mix of firm icy scoured surfaces, breakable crusts, and some softer surface snow (facets).

Weather and CURRENT CONDITIONS
weather summary

Snowfall started around 9 pm last night and has continued through this morning. The heaviest snow has fallen north of Hwy 50 with about 6 to 10 inches of accumulation. South of Hwy 50, 4 to 6 inches of new snow has accumulated so far. The forecast calls for the storm to move south today with additional accumulations across the mountains. As the storm moves south the winds will also shift to the NE. They have already done so north of Hwy 50. This system will also bring much colder temperatures for today and tonight. By tomorrow the sun should come back out as another high-pressure ridge starts building over the area. This will also bring warmer temperatures. Expect a warming trend for the rest 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: 13 to 17 deg. F.
Max. temperature: 38 to 42 deg. F.
Average ridgetop wind direction: Until 2 am: SW | After 2 am: NE
Average ridgetop wind speed: SW: 35 to 45 mph | NE: 20 mph
Maximum ridgetop wind gust: 80 mph
New snowfall: 4 to 10 inches
Total snow depth: 40 to 53 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Cloudy. Snow showers. Snow levels below 7000 feet. Chance of precipitation is 85%. Mostly cloudy then becoming partly cloudy. Slight chance of snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 10%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 21 to 26 deg. F. 11 to 16 deg. F. 31 to 37 deg. F.
Mid Slope Winds: Northeast 15 to 20 mph with gusts to 40 mph. Northeast 15 to 25 mph. Northeast 15 to 20 mph.
Expected snowfall: 80% probability of 1 to 3 inches. 20% probability of 3 to 5 inches. | SWE = up to 0.30 inch. No accumulation. | SWE = none. No accumulation. | SWE = none.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Cloudy. Snow showers. Snow levels below 7000 feet. Chance of precipitation is 85%. Mostly cloudy then becoming partly cloudy. Slight chance of snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 10%. Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 15 to 21 deg. F. 8 to 13 deg. F. 25 to 31 deg. F.
Ridge Top Winds: North 15 to 20 mph with gusts to 35 mph shifting to the northeast 15 to 30 mph with gusts to 60 mph in the afternoon. Northeast 30 to 40 mph with gusts to 75 mph. Northeast 35 to 55 mph with gusts to 100 mph decreasing to 25 to 35 mph with gusts to 70 mph in the afternoon.
Expected snowfall: 80% probability of 2 to 4 inches. 20% probability of 3 to 6 inches. | SWE = 0.15-0.35 inch. No accumulation. | SWE = less than 0.10 inch. No accumulation. | SWE = none.
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