THIS AVALANCHE FORECAST EXPIRED ON January 12, 2020 @ 6:53 am
Avalanche Forecast published on January 11, 2020 @ 6:53 am
Issued by Brandon Schwartz - Tahoe National Forest

Anticipate encountering unstable slabs of wind drifted snow in wind exposed areas near treeline and above treeline today. MODERATE avalanche danger exists above treeline and near treeline with LOW avalanche danger below treeline.

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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Winds shifted back to the SW yesterday morning and became gale force last night. This will have scoured and drifted any available snow in wind exposed areas, forming wind slabs in lee areas. Wind slabs composed both of drifted older snow and drifted new snow today are expected near treeline and above treeline on NW-N-NE-E-SE aspects. Avalanche size is expected mainly at D1 with size D2 possible in the more heavily wind drifted areas.

Wind, new snow, and potentially decreased visibility at times may challenge group communication today. Identify potentially unstable wind slabs by looking for blowing and drifting snow, recent cornice and wind pillow formations, lee areas of smooth looking slope, and snow surface cracking. When areas of concern are identified, make a plan within your group for how to move around these areas with an increased margin of safety.

recent observations
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* Several small (size D1) intentionally skier triggered wind slab avalanches occurred on Jan 8 & 9. These occurred along the Sierra Crest in the northern portion of the forecast area in above treeline and near treeline terrain on N-NE-E aspects.

* Weak snow in the upper snowpack (facets and low density DFs) around the Dec 12 and Jan 4 rain crusts are failing in snowpit tests when placed under an artificial new snow load. This is a weak layer of concern for future storms this week. Check out the loaded PST video from Jan 10.

* The middle and lower portions of the existing snowpack are consolidated, well bonded, and in good condition to handle new snow loading.

Weather and CURRENT CONDITIONS
weather summary

Gale force SW ridgetop winds and a little snow are expected today as the first in a series of weather systems moves through the forecast area. Winds have mixed down through the lower atmosphere, bringing strong gusts to the mid slope areas as well. Winds and snow showers will gradually decrease today, but winds will remain moderate to strong in speed tonight and tomorrow. Light snow showers are expected tomorrow with minimal additional accumulation. Two significant snowfall events are forecast for next week including what may turn out as our largest storm so far this winter. More information on these expected storms is available from 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: 17 to 21 deg. F.
Max. temperature: 35 to 39 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 45 mph
Maximum ridgetop wind gust: 83 mph
New snowfall: 1 inches
Total snow depth: 43 to 46 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 55%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%. Partly cloudy then becoming mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%.
Temperatures: 28 to 33. deg. F. 16 to 21. deg. F. 29 to 34. deg. F.
Mid Slope Winds: Southwest 20 to 35 mph with gusts to 70 mph decreasing to 15 to 25 mph with gusts to 50 mph in the afternoon. Southwest around 15 mph. Gusts up to 45 mph decreasing to 30 mph after midnight. Southwest 15 to 20 mph. Gusts up to 30 mph increasing to 40 mph in the afternoon.
Expected snowfall: 70% probability of 1 to 3 inches. 30% probability up to 1 inch. | SWE = less than 0.10 inch. No accumulation. | SWE = none. 20% probability up to 1 inch. 80% probability no accumulation. | SWE = trace amounts.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 55%. Partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 10%. Partly cloudy then becoming mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%.
Temperatures: 24 to 30. deg. F. 14 to 19. deg. F. 24 to 30. deg. F.
Ridge Top Winds: Southwest 30 to 50 mph with gusts to 90 mph decreasing to 25 to 35 mph with gusts to 65 mph in the afternoon. Southwest 20 to 30 mph with gusts to 60 mph. Southwest 20 to 30 mph with gusts to 65 mph.
Expected snowfall: 80% probability of 1 to 3 inches. 20% probability up to 1 inch. | SWE = up to 0.15 inch. No accumulation. | SWE = none. 20% probability up to 1 inch. 80% probability no accumulation. | SWE = trace amounts.
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