THIS AVALANCHE FORECAST EXPIRED ON February 22, 2017 @ 6:51 am
Avalanche Forecast published on February 21, 2017 @ 6:51 am
Issued by Brandon Schwartz - Tahoe National Forest

Areas of HIGH avalanche danger will continue to exist today at all elevations. Localized convective snow showers are expected to create periods of high intensity snowfall. Widespread avalanche activity occurred yesterday and likely continued to occur last night. Wind slabs and storm slabs remain ongoing avalanche problems.

Travel in or below avalanche terrain is not recommended. Avoid avalanche runout zones.

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Below Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Wind slabs remain an ongoing avalanche problem in many areas. The vast majority of wind slabs will be found near treeline and above treeline. Some wind slabs likely exist in below treeline areas due to the strength of the winds last night. The majority of wind slabs are expected to exist on NW-N-NE-E-SE-S aspects but could exist in isolated areas on SW-W aspects as well. Forecast wind speeds are fairly optimal for wind loading today.

Travel in or below avalanche terrain is not advised. Avoid avalanche runout zones.

Avalanche Problem 2: Storm Slab
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The mix of fluctuating snow level last night combined with high intensity snowfall is likely to have created storm slab instability within the recent new snow. Additional snowfall today and localized high intensity convective snow showers will allow for the continued development of storm slabs. Avalanche size could range from small to rather large depending on how much of the total storm snow is involved.

Travel in or below avalanche terrain is not recommended. Avoid avalanche runout zones.

recent observations
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Observations made yesterday on Andesite Peak (Donner Summit area) noted natural and human triggered avalanche activity in near treeline and below treeline areas. Storm slabs and wind slabs failing around 1 foot deep near the base of the recent storm snow were seen on NE-E aspects. Information received from the West Shore Tahoe area reported widespread avalanche activity with numerous crowns, cracks, and debris piles well below treeline and on relatively lower angle slopes in the Jakes Peak/Hidden Peak area.

Weather and CURRENT CONDITIONS
weather summary

An ongoing powerful storm system will continue to bring gale force SW wind and snow to the forecast area today. Last night new snow amounts of 10 to 20 inches accumulated above 8,000'. Snow levels rose to around 7,400' before lowering again to 6,000' and below. Ridgetop winds maxed out with sustained winds over 140 mph with max gusts to 199 mph over the Sierra Crest. Air temperatures are forecast to be colder today than yesterday with maximum day time air temperatures above 7,000' in the low 20s to low 30s. Snowfall today will be off and on in intensity. Most areas are expected to receive 6 to 12 inches of additional snow today. However, convective snow showers are forecast to produce localized snowfall rates up to 2 inches per hr and up to 18 inches of total daytime accumulation. This storm system is forecast to taper off tonight into tomorrow with continued SW wind at moderate to strong in speed.

 

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 23 to 30 deg. F.
Max. temperature: 31 to 34 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 70 mph
Maximum ridgetop wind gust: 199 mph
New snowfall: 15 to 30 inches
Total snow depth: 140 to 180 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Tuesday Tuesday Night Wednesday
Weather: Cloudy skies with snow. Cloudy skies with snow in the evening. Snow showers likely after midnight. Mostly cloudy skies. A chance of snow showers in the morning. A slight chance of snow showers in the afternoon.
Temperatures: 27 to 32 deg. F. 15 to 20 deg. F. 22 to 27 deg. F.
Mid Slope Winds: SW SW SW
Wind Speed: 30 to 45 mph with gusts to 75 mph, decreasing to 25 to 35 mph with gusts to 65 mph in the afternoon. 20 to 30 mph with gusts to 55 mph, decreasing to 15 to 20 mph with gusts to 40 mph after midnight. 15 to 25 mph with gusts to 35 mph.
Expected snowfall: Generally 5 to 10 in, locally up to 18 2 to 5 Up to 1
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Cloudy skies with snow. Cloudy skies with snow in the evening. Snow showers likely after midnight. Mostly cloudy skies. A chance of snow showers in the morning. A slight chance of snow showers in the afternoon.
Temperatures: 23 to 29 deg. F. 11 to 17 deg. F. 18 to 23 deg. F.
Ridge Top Winds: SW SW SW
Wind Speed: 40 to 60 mph with gusts to 135 mph, decreasing to 30 to 50 mph with gusts to 115 mph in the afternoon. 30 to 45 mph with gusts to 105 mph, decreasing to 20 to 30 mph with gusts to 75 mph after midnight. 20 to 35 mph. Gusts up to 70 mph decreasing to 60 mph in the afternoon.
Expected snowfall: Generally 6 to 12 in, locally up to 18 2 to 5 Up to 1
Disclaimer

This avalanche advisory is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This advisory 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 advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258