THIS AVALANCHE ADVISORY EXPIRED ON April 17, 2017 @ 6:59 am
Avalanche Advisory published on April 16, 2017 @ 6:59 am
Issued by Brandon Schwartz - Tahoe National Forest

MODERATE avalanche danger continues today at all elevations. Uncertainly exists in regards to the degree of loose wet avalanche problems today as well as lingering wind slab avalanche problems. Conservative decision making and conservative terrain selection are advised.

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: Loose Wet
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Near to above freezing air temperatures exist this morning at most mid and upper elevation locations. Transitional recent storm snow with thin melt-freeze crust exists in many areas. There is uncertainty as to how much sunshine will occur this morning and the associated amount of snow surface melt that will occur today. If last night's snow surface refreeze melts away, loose wet avalanche problems will exist again today. Increasing SW winds will slow snow surface cooling in wind exposed areas, but not in wind sheltered areas.

Be cognizant of and conservative with specific slopes that hold surface wet snow today, especially in areas of sun exposure and wind protection.

 

Avalanche Problem 2: Wind Slab
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Storm snow instabilities have been slow to stabilize in some areas near and above treeline on NW-N-NE aspects. This is possibly due to one or more layers of graupel present within the recent storm snow in some areas. Exercise conservative terrain selection and decision making in areas where signs of recent slab avalanche activity exist, even if the avalanches appear to be several days old. The same weak layer my still be an issue.

recent observations

A skier triggered wet snow avalanche was reported yesterday that occurred on Mt. Tallac in "The Cross". This avalanche occurred around 1 pm under warming conditions and was around 1 foot deep and 20 feet wide. As is typical with warming instability of recent storm snow, previous tracks existed on the slope prior to the avalanche occurrence. Observations made yesterday afternoon on Andesite Peak (Donner Summit area) revealed wet surface snow on all aspects up to the peak's summit at around 8,200'. Signs of loose wet instability were widespread with loose wet avalanche activity intentionally triggered on steep test slopes. Snowpit data collected yesterday on Red Lake Peak (Carson Pass area) revealed signs of ongoing instability within the recent storm snow on previously wind loaded slopes. Snowpit tests showed failures on a layer of graupel that may be associated with the recent avalanche activity in the area.

Weather and CURRENT CONDITIONS
weather summary

For today expect increasing cloud cover, above freezing air temperatures, and precipitation becoming possible this afternoon. A couple of weak weather systems will pass through the forecast area over the next couple of days. Snow levels are forecast in the 6,500' to 7,500' range this afternoon through Monday. Snow levels could be on the lower side of that range this afternoon and on the higher side of the range tomorrow afternoon. Overall snowfall amounts above 7,000' are expected at 6 inches or less today and tomorrow. A very small chance of higher snowfall amounts approaching 1 foot does exist. Ridgetop winds are on the increase today. Moderate to strong winds out of the SW are expected to reach gale force this evening. A slight decrease in wind speed is expected for tomorrow.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 33 to 39 deg. F.
Max. temperature in the last 24 hours: 37 to 48 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 29 mph
Maximum wind gust in the last 24 hours: 58 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 127 to 195 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy skies becoming cloudy. A chance of rain and snow in the afternoon. Cloudy with snow and rain likely in the evening. A chance of snow after midnight. Cloudy skies with a chance of showers in the morning. Rain and snow showers in the afternoon.
Temperatures: 45 to 50 deg. F. 29 to 34 deg. F. 39 to 47 deg. F.
Wind Direction: SW SW SW
Wind Speed: 15 to 25 mph. Gusts to 40 mph increasing to 55 mph in the afternoon. 20 to 35 mph. Gusts up to 70 mph decreasing to 50 mph after midnight. 15 to 25 mph with gusts to 45 mph.
Expected snowfall: Up to 1 in. Up to 3 in. Up to 2 in.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy skies becoming cloudy. A chance of snow in the afternoon. Cloudy with snow likely in the evening. A chance of snow after midnight. Cloudy skies with a chance of showers in the morning. Snow showers in the afternoon.
Temperatures: 40 to 46 deg. F. 27 to 32 deg. F. 35 to 43 deg. F.
Wind Direction: SW SW SW
Wind Speed: 20 to 35 mph. Gusts to 70 mph increasing to 80 mph in the afternoon. 45 to 55 mph with gusts to 100 mph, decreasing to 30 to 50 mph with gusts to 80 mph after midnight. 20 to 30 mph with gusts to 60 mph, increasing to 35 to 45 mph with gusts to 80 mph in the afternoon.
Expected snowfall: Up to 1 in. 2 to 4 in. Up to 2 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