THIS AVALANCHE FORECAST EXPIRED ON December 13, 2019 @ 6:59 am
Avalanche Forecast published on December 12, 2019 @ 6:59 am
Issued by Brandon Schwartz - Tahoe National Forest

MODERATE avalanche danger exists at all elevations. Wind drifted new snow over the highest elevations has created the potential for wind slab avalanches. Rain on snow has created the potential for loose wet avalanches.

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: Wind Slab
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Above the rain/snow line around 8,500' or so, wind drifted new snow will have formed some new wind slabs. These new wind slabs composed of dense wet snow are expected to be fairly small and difficult to trigger. Expect to find these wind slabs in lee areas near and above treeline on NW-N-NE-E-SE aspects. Avalanche size is expected at D1 with the potential for an isolated size D2.

Use clues such as cornices, wind pillows, and ridgetop wind scouring vs deposition to determine the areas where wind drifted snow has deposited as wind slabs. Account for how cliffs, rocks, trees, or terrain traps below could create injury or burial from what would otherwise be a small and inconsequential avalanche. The size and distribution of this avalanche problem are expected to increase over the next several days.

Avalanche Problem 2: Loose Wet
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High elevation rain on snow has created the potential for a loose wet avalanche problem. Loose wet avalanches could occur just about anywhere today. Locations above 8,000', especially on NW-N-NE aspects held cold snow, unaffected by warming and rain prior to this warming event. These areas where rain is or has fallen on cold snow are particularly prone to loose wet avalanches. Avalanche size up to D2 is possible. Isolated natural loose wet avalanches are not impossible today.

Roller balls are a sign of wet snow instability. Avoid traveling across or stopping below slopes where fresh roller balls are present.

recent observations
Submit Observations

Observations from around the forecast area over the past several days have indicated that the snowpack continues to gain strength with avalanche concerns limited to surface instabilities. The Dec 6 buried surface hoar layer continues to gain strength with little to no problematic snowpit test results observed. No avalanches are known to have occurred on this layer since Monday Dec 9.

Weather and CURRENT CONDITIONS
weather summary

Snow levels have been on the rise overnight as a relatively weak weather system moves through the area. Snow levels are forecast for around 8,500' today. Accumulating snowfall is limited to the highest elevation peaks within the forecast area with all other areas receiving rain. Precipitation is expected to taper off as the day progresses. Strong SW ridgetop winds are forecast to continue for the next several days. The next storm system arrives late Friday and is expected to bring lowering snow levels and significant snowfall. Check with NWS Reno for more details on this next storm.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 31 to 36 deg. F.
Max. temperature: 31 to 36 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 44 mph
Maximum ridgetop wind gust: 80 mph
New snowfall: Trace to 1 inches | Rain 0.1 to 0.4 inches
Total snow depth: 44 to 53 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Rain. Snow levels 8500. Chance of precipitation is 80%. Mostly cloudy. Rain and snow likely. Snow levels 7500 feet. Chance of precipitation is 60%. Mostly cloudy. Snow and a chance of rain. Snow levels 7000 feet. Chance of precipitation is 85%.
Temperatures: 39 to 44. deg. F. 30 to 35. deg. F. 35 to 40. deg. F.
Mid Slope Winds: Southwest 10 to 20 mph with gusts to 35 mph. Southwest 15 to 25 mph with gusts to 40 mph. Southwest 15 to 25 mph with gusts to 40 mph.
Expected snowfall: No accumulation. | SWE = 0.15-0.40 inch. Up to 1 inch. | SWE = up to 0.15 inch. 70% probability up to 2 inches. 30% probability of 2 to 3 inches. | SWE = up to 0.40 inch.
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy. Snow and rain. Snow levels 8500 feet. Chance of precipitation is 100%. Mostly cloudy. Chance of rain in the evening. Chance of snow through the night. Snow levels 7500 feet. Chance of precipitation is 60%. Mostly cloudy. Snow likely. Snow levels 7000 feet. Chance of precipitation is 70%.
Temperatures: 35 to 40. deg. F. 27 to 32. deg. F. 31 to 36. deg. F.
Ridge Top Winds: Southwest 35 to 55 mph with gusts up to 80 mph. Southwest 30 to 50 mph with gusts to 85 mph. Southwest 25 to 45 mph with gusts to 80 mph.
Expected snowfall: 70% probability of 1 to 3 inches. 30% probability of 3 to 5 inches. | SWE = 0.30-0.55 inch. 30% probability of 1 to 3 inches. 70% probability up to 1 inch. | SWE = up to 0.20 inch. 70% probability of 2 to 4 inches. 30% probability of 4 to 6 inches. | SWE = 0.20-0.45 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