THIS AVALANCHE ADVISORY EXPIRED ON February 6, 2015 @ 6:47 am
Avalanche Advisory published on February 5, 2015 @ 6:47 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger remains LOW for all elevations and aspects. Normal caution is advised. A powerful storm system moving into the forecast area is expected to create increased avalanche danger this weekend.

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: Normal Caution
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
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    Very Large
    Large
    Small

Despite above freezing air temperatues, a decent snow surface refreeze is expected to have occurred last night driven by radiational cooling under partly cloudy skies. Areas of surface wet snow are likely to form today, but convective cooling from strong to gale force winds, increasing cloud cover, and well established snowpack drainage are expected to keep any areas of instability from forming. Icy surfaces combined with gale force winds may make travel difficult in upper elevation and ridgetop areas.

recent observations

Recent observations from around the forecast area have shown that the snowpack is generally in good condition to handle new loading from rain and snow. Free water drainage from the snowpack is well established in the vast majority of areas below 8,000'. Near surface layers consist of a mix of well established melt-freeze on SE-S-SW aspects and a well bonded mix of crusts, rounds and rounding facets on W-NW-N-NE-E aspects. On some of these more northerly aspects rain and melt-freeze crusts are at the snow surface and in other areas they are buried several inches down. Some NW-N-NE aspect locations hold a notable layer of lower density rounding facets below the thickest rain crust in the upper third of the snowpack. This layer has been a focus for monitoring during the month of January and has yet to show signs that it will be problematic during the upcoming storm cycle. That said, it will remain a layer to watch once new snow loading begins.

Weather and CURRENT CONDITIONS
weather summary

Increasing cloud cover and strong southwest winds are expected today as the leading edge of a strong Pacific storm system moves into the region. The majority of precipitation over the forecast area is expected to hold off until late tomorrow. In the mean time, southwest winds have thoroughly mixed the atmosphere and prevented any air temperature inversion from forming last night. Air temperatures this morning in the 8,000' to 9,000' range are in the mid 30s to low 40s with warmer temperatures well into the 40s on the mountain valley floors. Ridgetop winds are expected to increase to gale force this afternoon with gusts to 100 mph later today and gusts to 125 mph tomorrow. Expected precipitation amounts Friday night/Saturday will depend highly on the exact track of the storm, but 1 to 3+ inches of rain and rain water equivalent are currently forecast with fluctuating snow levels that spend the majority of time in the 7,000' to 7,500' range. New snow amounts of 1 to 2 feet above 8,000' are possible. All of this is subject to change as the storm nears and the exact details become more clear. Check with NWS Reno for the latest updates.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 35 to 42 deg. F.
Max. temperature in the last 24 hours: 44 to 49 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 34 mph
Maximum wind gust in the last 24 hours: 60 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 21 to 32 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. Mostly cloudy skies. A slight chance of rain and snow after midnight. Mostly cloudy skies, becoming cloudy. A slight chance of rain and snow.
Temperatures: 42 to 52 deg. F. 32 to 39 deg. F. 43 to 49 deg. F.
Wind Direction: SW SW SW
Wind Speed: 25 to 40 mph wih gusts to 65 mph, increasing to 35 to 50 mph with gust to 80 mph in the afternoon. 40 to 55 mph with gusts to 90 mph. 40 to 55 mph with gusts to 90 mph.
Expected snowfall: 0 in. 0 to trace in. Up to 4 in.
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies. A slight chance of rain and snow after midnight. Mostly cloudy skies, becoming cloudy. A slight chance of rain and snow.
Temperatures: 42 to 49 deg. F. 27 to 34 deg. F. 34 to 41 deg. F.
Wind Direction: SW SW SW
Wind Speed: 40 to 55 mph with gusts to 80 mph, increasing to 55 to 65 mph with gusts to 100 mph. 55 to 70 mph with gusts to 105 mph. 60 to 80 mph with gusts to 125 mph.
Expected snowfall: 0 in. 0 to trace in. 1 to 4 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.