THIS AVALANCHE FORECAST EXPIRED ON December 14, 2019 @ 6:52 am
Avalanche Forecast published on December 13, 2019 @ 6:52 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger is increasing today. CONSIDERABLE avalanche danger is expected to develop this afternoon in above treeline and near treeline areas due to wind drifted snow forming into wind slabs. MODERATE avalanche danger is expected this afternoon below treeline due to the possibility of new snow forming into storm slabs.

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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Once snowfall intensifies today, wind slabs will grow in size and distribution. Areas of wind drifted snow are expected to form unstable wind slabs this afternoon in near treeline and above treeline terrain, mainly on NW-N-NE-E-SE aspects. The expected avalanche size is D2.

Use clues such as blowing snow and signs of past blowing snow including cornices, wind pillows, and scouring vs deposition patterns along ridgelines to identify the most likely location of wind slabs and make a plan to avoid them.

Avalanche Problem 2: Storm Slab
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New storm slabs are possible as an avalanche concern by sundown, becoming deeper and more widespread as new snow continues to accumulate during the evening hours in wind protected areas below treeline on all aspects. The expected avalanche size is D1 to D2.

Areas of snow surface cracking in wind protected areas are a sign of storm slab instability. Using lower angle slopes and avoiding steeper slopes above is a way to manage this problem. If storm slab instability does not form, expect loose dry avalanche problems (sluff) instead.

recent observations
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Some loose wet avalanches were noted yesterday near Mt. Lola (Independence Lake area) on steep N-NE aspect complex terrain at 8,000'. A few small wind slab avalanches that were a day or two old were also noted in this same location.

Snowpit data continues to show good bonding of the layers in the bottom and middle portions of the snowpack. The snowpack continues to gain complexity with various rain crusts. No problematic weak layer formation (faceting) around these crusts has been reported.

Weather and CURRENT CONDITIONS
weather summary

Another storm system will move into the region today. Snow levels are expected to start out around 7,500' and gradually decrease as the storm progresses. Ridgetop winds are forecast to remain strong in speed out of SW today and tonight. Precipitation is expected to begin around midday today, increasing in intensity through the afternoon and evening hours. New snow amounts for the next 24 hours are expected to reach 6 to 12 inches above 7,000' with the possibility of up to 18 inches over the Sierra Crest. A second weaker and colder weather system is forecast to move through the area Saturday night.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 28 to 32 deg. F.
Max. temperature: 32 to 36 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 45 mph
Maximum ridgetop wind gust: 92 mph
New snowfall: Trace to 1 inches
Total snow depth: 42 to 50 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Chance of snow and rain. Snow levels 7500 feet. Chance of precipitation is 100%. Cloudy. Snow and rain. Snow levels 7000 feet. Chance of precipitation is 100%. Mostly cloudy. Snow likely. Snow levels below 7000 feet. Chance of precipitation is 65%.
Temperatures: 35 to 40. deg. F. 26 to 31. deg. F. 29 to 34. deg. F.
Mid Slope Winds: Southwest 15 to 30 mph with gusts to 50 mph. Southwest 15 to 25 mph with gusts to 45 mph. Southwest 15 to 25 mph. Gusts up to 40 mph decreasing to 30 mph in the afternoon.
Expected snowfall: 80% probability of 1 to 3 inches. 20% probability of 3 to 6 inches. | SWE = 0.25-0.50 inch. 70% probability of 4 to 8 inches. 30% probability of 8 to 12 inches. | SWE = 0.50-0.75 inch. 80% probability of 1 to 3 inches. 20% probability of 3 to 5 inches. | SWE = up to 0.15 inch.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Chance of snow in the morning, then snow in the afternoon. Snow levels 7500 feet. Chance of precipitation is 100%. Cloudy. Snow. Snow levels 7000 feet. Chance of precipitation is 100%. Mostly cloudy. Snow likely. Snow levels below 7000 feet. Chance of precipitation is 70%.
Temperatures: 32 to 37. deg. F. 22 to 27. deg. F. 25 to 30. deg. F.
Ridge Top Winds: Southwest 30 to 50 mph with gusts to 75 mph. Southwest 30 to 50 mph decreasing to 25 to 40 mph after midnight. Gusts up to 70 mph. Southwest 15 to 30 mph. Gusts up to 50 mph decreasing to 40 mph in the afternoon.
Expected snowfall: 70% probability of 2 to 4 inches. 30% probability of 4 to 7 inches. | SWE = 0.30-0.55 inch. 70% probability of 7 to 10 inches. 30% probability of 10 to 16 inches. | SWE = 0.65-1.10 inches. 80% probability of 1 to 3 inches. 20% probability of 3 to 5 inches. | SWE = up to 0.15 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