THIS AVALANCHE FORECAST EXPIRED ON January 25, 2020 @ 6:55 am
Avalanche Forecast published on January 24, 2020 @ 6:55 am
Issued by Brandon Schwartz - Tahoe National Forest

A low likelihood high consequence persistent slab avalanche problem lingers below treeline and near treeline with ongoing isolated instability. Lingering wet snow surface conditions below 8,500' may allow for some very small loose wet avalanches. Wind and light snow last night may have created isolated slabs of wind drifted snow near and above treeline. MODERATE avalanche danger exists at all elevations.

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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Lingering, isolated instability exists below treeline and near treeline on NW-N-NE-E aspects. The sugary Jan 4 crust/facet persistent weak layer in these areas is gaining strength but not at the same rate in all locations. Spatial variability of stable vs unstable is increasing. In most below treeline locations, this weak layer is buried 1 to 2 feet below the snow surface. In some near treeline areas, this weak layer is buried up to 8 feet below the surface under wind drifted snow. Human triggered avalanches size D2 to D3 have become unlikely on a regional scale, but an isolated avalanche is still a concern.

A low likelihood high consequence avalanche problem is what remains at this time. We are close to but not quite past this avalanche problem on a regional scale due to the continued signs of isolated instability. Make conservative terrain and route selections in any areas where unstable snowpit test results or other signs of instability exist.

Avalanche Problem 2: Loose Wet
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Wet snow surface conditions will remain in some areas today below 8,500'. Some rollerballs or very small loose wet avalanches are possible today. Avalanche size is expected at D1. Problematic consequences of being caught would come from downslope terrain hazards such as cliffs and terrain traps below.

Avalanche Problem 3: Wind Slab
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In isolated areas above treeline and near treeline, small unstable slabs of wind drifted snow may have formed last night. Slopes below cornice features are the most suspect. Avalanche size is expected at D1 with up to D2 possible in the most heavily wind drifted areas where over two inches of new snow fell last night. Move cautiously around cornice areas in locations where 2+ inches of new snow are present.

recent observations
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* Wetted snow surfaces were reported yesterday from the Echo Summit and West Shore Tahoe areas with some rollerballs and pin wheels occurring.

* Surface hoar 2-9 mm in size was reported yesterday on northerly aspects in the Echo Summit and Luther Pass areas.

* Snowpit tests targeting the persistent Jan 4 crust/facet layer have shown increasingly variable results over the past several days with isolated areas of unstable test results continuing. Clearly unstable snowpit test results were observed yesterday on Stoney Ridge (West Shore Tahoe area) while at the same time several snowpits in similar terrain on Waterhouse Peak (Luther Pass area) gave no indications of ongoing instability. Five days have past since an avalanche was reported to have failed on the Jan 4 weak layer.

Weather and CURRENT CONDITIONS
weather summary

A weak weather system will linger in the region this morning before exiting this afternoon. Snow levels started out around 8,500'-8,800' last night and lowered to around 7,500' prior to sunrise. Snow levels are forecast to lower to around 7,000' this morning with the last of the precipitation. Partial clearing of cloud cover is expected as the day progresses. Air temperatures will warm above freezing for most elevations. Moderate to strong SW ridgetop winds are forecast to continue through today, decreasing tonight into tomorrow. A break in the weather will occur tonight and tomorrow before the next storm system affects the area tomorrow evening into Sunday morning.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 29 to 31 deg. F.
Max. temperature: 38 to 40 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 22 mph
Maximum ridgetop wind gust: 68 mph
New snowfall: 1 to 3 inches
Total snow depth: 42 to 53 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 then becoming partly cloudy. Isolated showers in the morning. Snow levels 7500 feet decreasing to below 7000 feet in the afternoon. Chance of precipitation is 20%. Mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Mostly cloudy. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 5%.
Temperatures: 37 to 42. deg. F. 25 to 30. deg. F. 42 to 47. deg. F.
Mid Slope Winds: Southwest 10 to 20 mph with gusts to 35 mph. West to southwest up to 10 mph. Light winds.
Expected snowfall: Up to 1 inch. | SWE = less than 0.10 inch. No accumulation. | SWE = none. No accumulation. | SWE = none.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Mostly cloudy then becoming partly cloudy. Isolated snow showers in the morning. Snow levels 7500 feet decreasing to below 7000 feet in the afternoon. Chance of precipitation is 20%. Mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Mostly cloudy. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 5%.
Temperatures: 33 to 39. deg. F. 23 to 28. deg. F. 38 to 44. deg. F.
Ridge Top Winds: Southwest 20 to 35 mph with gusts to 55 mph. Southwest 15 to 25 mph with gusts to 40 mph. Southwest 10 to 20 mph.
Expected snowfall: 80% probability up to 1 inch. 20% probability of 1 to 2 inches. | SWE = less than 0.15 inch. No accumulation. | SWE = none. No accumulation. | SWE = none.
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