THIS AVALANCHE FORECAST EXPIRED ON January 4, 2021 @ 6:57 am
Avalanche Forecast published on January 3, 2021 @ 6:57 am
Issued by Brandon Schwartz - Tahoe National Forest

The likelihood of triggering an avalanche has gradually decreased but the consequences have not. Isolated areas of unstable snow linger due to a persistent slab avalanche problem. Any isolated avalanches today are likely to be larger than expected. MODERATE avalanche danger lingers at all elevations. Increasing avalanche danger is expected tomorrow.

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: Persistent Slab
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The likelihood of triggering an avalanche has trended downwards over the last few days. Signs of instability in the deeper old snow layers are becoming increasingly isolated. The most recent signs of obvious persistent slab instability were reported on January 1. Unfortunately, the consequences of triggering an avalanche remain elevated with the potential for wide propagation and larger than expected avalanches. Mid slope avalanches and avalanches occurring on slopes with numerous tracks are also a possibility. Concern for this avalanche problem exists at all elevations on W-NW-N-NE-E aspects.

The easy way to deal with this avalanche problem is to choose to travel only on sub 30 degree angle slopes without steeper slopes above or to the side. Otherwise, moving into steeper terrain should utilize cautious, skilled, unrushed snowpack assessment. Avoid writing off any clues to instability in the deeper old snow layers regardless of isolated occurrence.

 Photo: Signs of persistent slab instability on January 1 near Brockway Summit, CA.

recent observations
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* An unforecast mist/light rain event affected most of the forecast area yesterday. Some minor roller ball activity was reported. A thin new crust is likely to have formed on the snow surface last night in areas below 8,000' and possibly up to 9,000' in some locations.

* Newly formed wind slabs were dense and difficult to trigger yesterday.

* The Dec 11 PWL continues to gain strength but an overall poor snowpack structure remains. The most recent signs of instability on this layer were reported from near Brockway Summit on January 1 with snowpack collapsing, whumpfing, test slope failure, and unstable snowpit test results.

* Surface hoar buried within the top few inches of the snowpack has been reported from some locations.

Weather and CURRENT CONDITIONS
weather summary

New snowfall last night was minimal. Mostly cloudy skies and above freezing air temperatures are forecast for today. Ridgetop winds remain out of the W to SW this morning and are gradually decreasing to moderate speed. A significant storm system will impact the forecast area starting early tomorrow morning with gale force SW winds and increasingly intense snowfall through the day, peaking in intensity during the afternoon and evening.  Storm total snowfall of 10 to 18 inches from 1 to 2 inches of SWE is the current forecast. A break in the weather is expected on Tuesday. The next weather system to affect the region is forecast for Wednesday.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 24 to 30 deg. F.
Max. temperature: 29 to 33 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 44 mph
Maximum ridgetop wind gust: 69 mph
New snowfall: Trace to 1 inches
Total snow depth: 29 to 36 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Snow levels below 7000 feet increasing to 7000 feet in the afternoon. Chance of precipitation is 10%. Mostly cloudy. Slight chance of snow showers after midnight. Snow levels below 7000 feet. Chance of precipitation is 10%. Cloudy. Snow likely in the morning, then snow in the afternoon. Snow levels 7000 feet. Chance of precipitation is 95%.
Temperatures: 35 to 40. deg. F. 26 to 31. deg. F. 33 to 38. deg. F.
Mid Slope Winds: Southwest around 15 mph with gusts to 35 mph in the morning becoming light. Light winds becoming southwest around 15 mph with gusts to 25 mph after midnight. Southwest 15 to 20 mph with gusts to 45 mph increasing to 20 to 30 mph with gusts to 60 mph in the afternoon.
Expected snowfall: No accumulation. | SWE = none. Up to 1 inch. | SWE = less than 0.10 inch. 70% probability of 2 to 6 inches. 30% probability of 6 to 10 inches. | SWE = 0.50-0.75 inch.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Snow levels below 7000 feet increasing to 7000 feet in the afternoon. Chance of precipitation is 10%. Mostly cloudy. Slight chance of snow showers after midnight. Snow levels below 7000 feet. Chance of precipitation is 15%. Cloudy. Snow likely in the morning, then snow in the afternoon. Snow levels 7000 feet. Chance of precipitation is 95%.
Temperatures: 32 to 38. deg. F. 24 to 29. deg. F. 29 to 34. deg. F.
Ridge Top Winds: West 15 to 30 mph. Gusts up to 60 mph decreasing to 40 mph in the afternoon. Southwest 15 to 25 mph. Gusts up to 40 mph increasing to 50 mph after midnight. Southwest 25 to 35 mph with gusts to 75 mph increasing to 40 to 65 mph with gusts to 115 mph in the afternoon.
Expected snowfall: No accumulation. | SWE = none. Up to 1 inch. | SWE = less than 0.10 inch. 70% probability of 3 to 9 inches. 30% probability of 9 to 14 inches. | SWE = 0.60-0.85 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