THIS AVALANCHE ADVISORY EXPIRED ON April 4, 2014 @ 6:53 am
Avalanche Advisory published on April 3, 2014 @ 6:53 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger is LOW for all elevations and aspects. Isolated areas of wind slab and persistent slab instability may exist, especially in complex or extreme terrain. Normal caution is advised.

1. Low

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Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Wind Slab
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For the most part, lingering wind slabs from Tuesday have gained strength and have become very difficult to trigger. Lingering instability is most likely to be encountered near and above treeline on NW-N-NE aspects, especially in complex or extreme terrain where stabilization rates can be slower and slopes may be unsupported above large rocks and cliff bands. 

Avalanche Problem 2: Persistent Slab
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The near crust facet layer located at the base of the recent storm snow is now buried 1.5 to 4+ feet deep. In many areas, snowpit tests have indicated that this weak layer has adjusted to the snow load above it. Human triggering of this weak layer has become difficult, especially in areas on NW-N-NE aspects where the weak layer is deeply buried. Triggering is most likely to occur in a location where the weak layer is closer to the surface. This is most commonly found in complex or extreme terrain where rock features can bring the weak layer closer to the snow surface creating shallow snow trigger points.

advisory discussion

Another short period of rapid warming is expected this morning. Below average air temperatures and increasing afternoon cloud cover are expected to help keep areas of wet snow instability to a minimum again today. Isolated areas of roller balls and small pinwheels may occur on all aspects as snow falls off of trees and rocks. The expected minimal amount of loose wet instability that occurs today is not expected to involve loose wet avalanches. If cloud cover increases slower than forecast or air temperatures warm more than forecast, the amount of loose wet instability will be greater than forecast.

recent observations

Observations made yesterday on Rubicon Peak (West Shore Tahoe area) revealed little in the way of snowpack instability. Snowpit tests investigating wind slabs and persistent slabs that had been reactive in this area three days prior indicated an overall improvement in snowpack stability. A short period of rapid warming was observed during the morning hours, but was shut down by increasing afternoon cloud cover and snow showers. A few isolated roller balls were observed on SE aspects below 7,000'. A thin layer of wet surface snow was noted on all aspects below 7,600' at 2 pm. That thin layer of wet snow is expected to have formed a melt-freeze surface crust last night.

Weather and CURRENT CONDITIONS
weather summary

A weak weather system is approaching the region. Increasing cloud cover will occur today with high level clouds lowering and thickening this afternoon. Isolated snow showers are possible beginning this afternoon and continuing through Friday. Snow level is expected to fluctuate between 4,500' and 6,000' today, tonight, and tomorrow. New snow amounts will likely be minimal. A quick inch of accumulation will be possible during afternoon convective snow showers, more likely tomorrow afternoon than this afternoon. Ridgetop winds remain out of the east this morning, but are expected to shift to the southwest by this afternoon. Wind speeds will generally remain light today, increasing to moderate speed for tonight and tomorrow. Maximum daytime air temperatures for today will reach 30 to 40 degrees for areas above 7,000'.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 19 to 25 deg. F.
Max. temperature in the last 24 hours: 31 to 36 deg. F.
Average wind direction during the last 24 hours: Northeast
Average wind speed during the last 24 hours: 14 mph
Maximum wind gust in the last 24 hours: 24 mph
New snowfall in the last 24 hours: 0 to trace inches
Total snow depth: 59 to 73 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy skies becoming mostly cloudy. Isolated snow showers in the afternoon. Cloudy skies with isolated snow showers. Cloudy skies with scattered snow showers.
Temperatures: 33 to 40 deg. F. 16 to 23 deg. F. 27 to 34 deg. F.
Wind Direction: Southwest Southwest West
Wind Speed: Light winds increasing to 10 to 15 mph in the afternoon. 10 to 15 mph with gusts to 25 mph in the evening, becoming light. 10 to 15 mph. Gusts up to 25 mph in the afternoon.
Expected snowfall: 0 to trace in. 0 to trace in. Trace to 2 in.
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy skies becoming mostly cloudy. Isolated snow showers in the afternoon. Cloudy skies with isolated snow showers. Cloudy skies with scattered snow showers.
Temperatures: 29 to 35 deg. F. 12 to 19 deg. F. 25 to 31 deg. F.
Wind Direction: Southwest Southwest West
Wind Speed: Light winds increasing to 10 to 15 mph with gusts to 25 mph in the afternoon. 15 to 20 mph. Gusts to 35 mph decreasing to 25 mph after midnight. 15 to 20 mph with gusts to 30 mph.
Expected snowfall: 0 to trace in. 0 to trace in. Trace 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.