THIS AVALANCHE ADVISORY EXPIRED ON February 7, 2017 @ 7:00 am
Avalanche Advisory published on February 6, 2017 @ 7:00 am
Issued by Steve Reynaud - Tahoe National Forest

High avalanche danger will exist throughout today due to wind slab, storm slab, and loose wet avalanche problems.  Very dangerous avalanche conditions exist with natural avalanches likely and human triggered avalanches very likely.  Travel in avalanche terrain is not recommended.  Conditions will further deteriorate tonight as an atmospheric river brings additional heavy rain and high elevation snow to our area.

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 will be very likely on NW-N-NE-E-SE aspects in near and above treeline terrain as additional snow and gale force SW winds impact our area today.  Wind slabs could also develop on other aspects, in unusual areas below treeline, and much farther downslope than normal with wind gusts forecasted to be 130mph over the higher ridges.  Large and fragile cornices exist along ridgelines and should be avoided.  Whiteout conditions with limited visibility is expected today.

Travel in avalanche terrain is not recommended.  Avoid wind loaded terrain and runout zones below wind loaded terrain.   

Avalanche Problem 2: Storm Slab
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Storm slabs will continue to develop on all aspects in protected near treeline and below treeline terrain as snowfall continues.  These storm slabs could have an upside down storm snow structure as temperatures fluctuate through this storm cycle.  Clues such as snow surface cracking may indicated storm slab development.  Travel in or around avalanche terrain is not recommended.

Avalanche Problem 3: Loose Wet
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Areas of rain on snow today will be prone to loose wet avalanche activity.  Snow level is forecasted to remain near or below 6500' through today.  If snow levels rise more than forecasted loose wet avalanches could become more widespread.  Loose wet avalanche activity today could be either natural or human triggered.  Terrain traps such as creek beds and road cuts could increase the depth of avalanche debris associated with otherwise small loose wet avalanches.

recent observations

Observations were made and received yesterday from Carpenter Ridge (Independence Lake area), Waterhouse Peak (Luther Pass area), and Andesite Peak (Donner Summit area).  Heavy amounts of blowing snow were observed at all locations throughout the day with strong to gale force SW winds.  Several test slopes at Carpenter Ridge and Waterhouse Peak did not show signs of instability.  Many areas of cornice failures were observed along ridgelines in the Carpenter Peak area and also the Donner Summit area.

Weather and CURRENT CONDITIONS
weather summary

The first in a series of 3 storms is currently impacting our area with moderate to heavy snowfall.  Snow levels are currently in the 6000-6500' level and should remain consistent throughout today.  The next storm is expected this afternoon with heavier precipitation that will last through Tuesday.  Snow levels with this storm will rise dramatically overnight up to 8000-9000' with 6 to 8'' of precipitation expected.  The 3rd storm is expected Thursday night into Friday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 25 to 27 deg. F.
Max. temperature in the last 24 hours: 30 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 50 to 70 mph
Maximum wind gust in the last 24 hours: 122 mph
New snowfall in the last 24 hours: 6 to 12 inches
Total snow depth: 108 to 145 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Cloudy. Snow. Cloudy. Snow changing to rain after midnight. Cloudy. Rain and snow.
Temperatures: 30 to 33 deg. F. 30 to 33 deg. F. 38 to 43 deg. F.
Wind Direction: SW SW SW
Wind Speed: 30 to 45mph with gusts to 90mph. 25 to 40mph with gusts to 85mph. 25 to 40mph with gusts to 85mph.
Expected snowfall: 6 to 10 in. 4 to 10 in. 0 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Cloudy. Snow. Cloudy. Snow. Rain may mix with snow at 8000'. Cloudy. Snow and rain. Snow level 8000-8500'.
Temperatures: 29 to 33 deg. F. 29 to 34 deg. F. 36 to 41 deg. F.
Wind Direction: SW SW SW
Wind Speed: 60 to 80mph with gusts to 130mph. 55 to 75mph. Gusts to 130mph increasing to 140mph after midnight. 60 to 80mph with gusts to 140mph.
Expected snowfall: 6 to 12 in. 8 to 18 in. 12 to 18 in.
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