THIS AVALANCHE FORECAST EXPIRED ON December 12, 2020 @ 6:51 am
Avalanche Forecast published on December 11, 2020 @ 6:51 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

Today, avoiding obstacles and dealing with variable snow surfaces still remains the primary concern for backcountry travelers. Things will change during the night as new snow and wind will create avalanche problems on top of the shallow snowpack. The avalanche danger remains LOW at all elevations today, but it will INCREASE tonight and tomorrow. 

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Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Normal Caution
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The uneven and variable snow surfaces and a plethora of rocks, stumps, logs, and other obstacles will continue to make backcountry travel challenging today. Falls and collisions with these obstacles could damage equipment and injure people. Moving at slower speeds on more mellow terrain and being observant can make avoiding obstacles easier and snow travel more fun.

Conditions will change as new snow and wind impact the forecast area tonight and tomorrow. The forecasted snowfall amounts will hide some of the existing obstacles making them harder to see and easier to hit. The snow and wind will also create avalanche problems for tomorrow including slabs of wind drifted snow and potentially some slabs of storm snow in more sheltered areas.

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* A mostly supportable snowpack 1-2 ft. deep exists on northerly aspects above 8600 ft. in the Mt. Rose area, above 7000 ft. along the northern Sierra Crest, and above 8000 ft. along the southern Sierra Crest. 

* The snow surface varies widely with wind-scoured and sculpted surfaces in exposed near and above treeline terrain. More sheltered areas hold a mix of firm melt-freeze snow, breakable crusts, and some areas of soft surface snow (near-surface facets) on sheltered northerly aspects. The near and below treeline northerly aspects hold the most snow. Significant snow-melt has occurred on the southerly aspects leaving exposed ground on many of these slopes.

* Since our last storm on Nov. 18, mostly clear skies, long cold nights, and low sun angles have allowed a layer of weak sugary snow (near-surface facets) to form on sheltered northerly aspects. As new snow accumulates on top of this potential weak layer, it could overload the layer, and avalanche activity may result.

Weather and CURRENT CONDITIONS
weather summary

Cloud cover and winds should increase today ahead of a storm expected to arrive this evening. W and SW winds should remain strong through midday tomorrow before they shift to the north and decrease some. Snow should start to accumulate overnight with snowfall continuing through midday Saturday. Snow levels look like they will fluctuate and potentially rise to between 6500 and 7000 ft. during the storm. The forecast calls for 3 to 8 inches above 6500 ft. with a chance for up to 12 inches in some places along the Sierra Crest by midday tomorrow. Check-in with the Reno NWS for more details.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 22 to 29 deg. F.
Max. temperature: 34 to 37 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 20 to 30 mph
Maximum ridgetop wind gust: 61 mph
New snowfall: 0 inches
Total snow depth: 14 to 17 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. Snow levels below 7000 feet. Chance of precipitation is 10%. Mostly cloudy. Chance of snow in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 85%. Mostly cloudy. Snow in the morning, then chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 80%.
Temperatures: 33 to 38 deg. F. 24 to 30 deg. F. 32 to 37 deg. F.
Mid Slope Winds: West 10 to 20 mph with gusts to 35 mph. Southwest 15 to 25 mph. Gusts up to 40 mph. Northwest 15 to 25 mph with gusts to 40 mph.
Expected snowfall: No accumulation. | SWE = none. 80% probability of 2 to 4 inches. 20% probability of 4 to 6 inches. | SWE = 0.25-0.50 inch. 60% probability of 2 to 4 inches. 40% probability of 1 to 2 inches. | SWE = 0.15-0.40 inch.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 5%. Mostly cloudy. Chance of snow in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 85%. Mostly cloudy. Snow in the morning, then chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 85%.
Temperatures: 29 to 35 deg. F. 20 to 28 deg. F. 29 to 34 deg. F.
Ridge Top Winds: West 20 to 30 mph with gusts to 60 mph. Southwest 30 to 45 mph increasing to 35 to 55 mph after midnight. Gusts up to 90 mph. West 30 to 45 mph becoming north 20 to 30 mph in the afternoon. Gusts up to 70 mph.
Expected snowfall: No accumulation. | SWE = none. 80% probability of 3 to 6 inches. 20% probability of 6 to 8 inches. | SWE = 0.30-0.55 inch. 60% probability of 4 to 8 inches. 40% probability of 2 to 4 inches. | SWE = 0.40-0.65 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