THIS AVALANCHE FORECAST EXPIRED ON February 21, 2019 @ 6:58 am
Avalanche Forecast published on February 20, 2019 @ 6:58 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

MODERATE avalanche danger still exists near and above treeline due to the potential for lingering wind slabs in some terrain. Below treeline the avalanche danger is LOW.

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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Strong and shifting winds have left a variety of firm and soft wind slabs, cornices, and wind scoured surfaces on exposed near and above treeline slopes. Most of the wind slabs should have become more difficult to trigger, but some human-triggered wind slabs may still remain possible today. Unsupported slopes, gullies, couloirs, cliffy areas, and other complex or extreme terrain represent the best places to find a lingering wind slab. Today's new snow and wind could form some new wind slabs as well, but these should remain small in most places due to the limited amount of new snow expected. 

Identify the specific terrain where wind slabs may exist using clues like blowing snow, cornices above a slope, firm hollow sounding snow, and other wind created surface textures. Softer more consistent snow should still exist in most sheltered areas and could provide better recreation conditions with fewer chances for encountering wind slabs or firm wind scoured surfaces.

recent observations
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* Some small skier-triggered cracking was reported in firm wind slabs on W aspects in the Mt. Judah area and on upper elevation E aspects on Mt. Rose yesterday.

* Observers also saw ongoing wind transport near ridgelines on Deep Creek Peak, Ralston Peak, and on the peaks west of Luther Pass. Widespread signs of wind scouring including sastrugi, exposed rain crusts, and other firm surfaces existed in exposed near and above terrain and along ridgelines across the region.

* Observations from sheltered areas in the Donner Summit region, in Deep Creek, on Powderhouse Peak, on Flagpole Peak, and on Trimmer Peak all found soft snow with no signs of slab instabilities. Some surface hoar existed in the Mt Judah area, the Deep Creek area, and in the meadow near Powderhouse. 

* By the afternoon, some warming snow and thin sun crusts existed on southerly sun-exposed aspects on Mt Rose and Mt. Judah. Observers reported some small skier triggered loose wet instabilities in a steep SE facing gully on Mt. Rose. Some low elevation E aspects also had thin sun crusts on Mt. Judah.

Weather and CURRENT CONDITIONS
weather summary

The winds shifted to the SW and increased in strength overnight. They should continue through today before shifting back to the NW/N tonight and NE tomorrow as the storm departs. Light snow showers started this morning as the first band of precipitation has moved into the region. After a short break, another band of snow should push into the area later today. Snowfall should start to taper off overnight but some showers may linger into tomorrow especially in areas where lake effect snow can occur. Accumulations should remain on the lighter side with 2 to 6 inches forecast by tomorrow morning in most areas.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 12 to 18 deg. F.
Max. temperature: 25 to 33 deg. F.
Average ridgetop wind direction: NE shifting to SW yesterday evening
Average ridgetop wind speed: 25 to 35 mph
Maximum ridgetop wind gust: 79 mph
New snowfall: trace to 0 inches
Total snow depth: 103 to 145 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Scattered snow showers in the morning, then widespread snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Widespread snow showers in the evening then scattered snow showers after midnight. Snow levels below 7000 feet. Chance of precipitation is 60%. Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 40%.
Temperatures: 21 to 26 deg. F. 7 to 12 deg. F. 19 to 24 deg. F.
Mid Slope Winds: Southwest around 15 mph with gusts to 35 mph. Northwest around 15 mph with gusts to 25 mph in the evening becoming light. Northeast around 15 mph with gusts to 30 mph.
Expected snowfall: 80% probability of 1 to 4 inches. 20% probability of 4 to 6 inches. | SWE = up to 0.20 inch. 80% probability of 1 to 3 inches. 20% probability of 3 to 4 inches. | SWE = up to 0.15 inch. 60% probability up to 1 inch. 40% probability of 1 to 3 inches. | SWE = less than 0.10 inch.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Scattered snow showers in the morning, then widespread snow showers in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Widespread snow showers in the evening then scattered snow showers after midnight. Snow levels below 7000 feet. Chance of precipitation is 60%. Mostly cloudy. Chance of snow showers. Snow levels below 7000 feet. Chance of precipitation is 45%.
Temperatures: 16 to 22 deg. F. 4 to 9 deg. F. 10 to 16 deg. F.
Ridge Top Winds: Southwest 15 to 30 mph. Gusts up to 60 mph decreasing to 40 mph in the afternoon. North 15 to 25 mph with gusts to 40 mph. Northeast 15 to 25 mph with gusts to 45 mph.
Expected snowfall: 80% probability of 1 to 4 inches. 20% probability of 4 to 6 inches. | SWE = up to 0.20 inch. 80% probability of 1 to 4 inches. 20% probability of 4 to 6 inches. | SWE = up to 0.15 inch. 60% probability up to 1 inch. 40% probability of 1 to 3 inches. | SWE = up to 0.10 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