THIS AVALANCHE ADVISORY EXPIRED ON March 22, 2015 @ 6:47 am
Avalanche Advisory published on March 21, 2015 @ 6:47 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger is LOW for all elevations and aspects. Minor loose wet instabilities are expected during the afternoon hours. Loose wet avalanches large enough to bury or injure a person are unlikely. Normal caution is advised. Sufficient snow cover for avalanche activity on SE-S-SW-W aspects exists only in isolated portions of the forecast area. Much deeper, continuous snow cover exists on NW-N-NE-E aspects.

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
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

With clearing skies overnight and near to below freezing air temperatures, a strong overnight snow surface refreeze is expected to have occurred due to radiational cooling. As daytime warming progresses, areas of surface wet snow will form on sun exposed slopes. Increasing cloud cover today is not expected to be as thick as yesterday and therefore will not have as great of an impact on slowing the melting process during the mid day and afternoon hours. With the snowpack already subject to periods of rain and prolonged melt earlier this winter, free water drainage from the snowpack is well established. With little to no snow cover on the vast majority of SE-S-SW-W aspects, instability concerns are confined to highly localized areas on those aspects. E aspects continue to hold significant snow cover around the vast majority of the forecast area and will experience surface wet snow formation up to several inches deep by this afternoon. With free water drainage well established, wet snow instability is expected to be limited to human triggered roller balls and human triggered loose wet sluffs in steep terrain that require a push to set into motion. Loose wet avalanches large enough to bury or injure a person remain unlikely at this time.

recent observations

Observations made yesterday on Relay Peak (Mount Rose area) revealed that a strong snow surface refreeze had occurred in the area overnight. Increasing cloud cover during the morning hours greatly slowed the rate of snow surface melt. Travel on E-SE-S-SW aspects between 8,500' and 10,100' between 10 am and 1 pm revealed no more than 2 inches of wet surface snow on top of ski and boot supportable melt-freeze crust. No evidence of wet snow instability was observed prior to departure from the area at 1 pm. Snowpit data collected on an E aspect at 10,050' indicated that only the top 7 inches of the snowpack had been affected by melt-freeze at that elevation. Below the top 7 inches a well bonded, rounded snowpack with a temperature profile approaching isothermal was observed in the snowpit. Recent snowpit data collected on E aspects on Carson Pass and on Mt. Judah (Donner Summit area) at 8,900' and 8,100' respectively indicated that the full height of the snowpack had been subjected to melt-freeze.

Across the forecast area in general, sufficient snow cover for avalanche activity on SE-S-SW-W aspects exists only in isolated areas. Much deeper, continuous snow cover exists on NW-N-NE-E aspects.

Weather and CURRENT CONDITIONS
weather summary

Cloud cover from the weather system that passed north of the forecast area yesterday cleared out overnight. Sunny skies this morning will give way to increasing mid to high level cloud cover this afternoon ahead of the next weather system expected to bring precipitation to the forecast area beginning late tomorrow. Remote sensors are reporting air temperatures this morning in the mid 20s to mid 30s for areas 8,000' to 9,600'. Maximum daytime air temperatures are forecast to reach the low 40s to mid 50s today for areas above 7,000'. Ridgetop winds remain out of the southwest this morning and are gradually decreasing in speed after peaking last night. Southwest ridgetop winds are forecast to continue at moderate speed through tomorrow.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 31 to 37 deg. F.
Max. temperature in the last 24 hours: 49 to 51 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 27 mph
Maximum wind gust in the last 24 hours: 51 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 18 to 40 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Sunny skies, becoming mostly cloudy. Mostly cloudy skies. Mostly cloudy skies. A slight chance of snow showers in the afternoon.
Temperatures: 48 to 54 deg. F. 23 to 30 deg. F. 44 to 50 deg. F.
Wind Direction: SW SW SW
Wind Speed: 10 to 15 mph. Gusts up to 25 mph in the afternoon. 15 to 20 mph with gusts to 30 mph in the evening, becoming light. 15 to 20 mph with gusts to 30 mph, increasing to 25 to 30 mph with gusts to 45 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 to trace in.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Sunny skies, becoming mostly cloudy. Mostly cloudy skies. Mostly cloudy skies. A slight chance of snow showers in the afternoon.
Temperatures: 42 to 48 deg. F. 22 to 29 deg. F. 40 to 46 deg. F.
Wind Direction: SW SW SW
Wind Speed: 25 to 35 mph with gusts to 50 mph. 25 to 30 mph with gusts to 45 mph, decreasing to 10 to 15 mph with gusts to 25 mph after midnight. 25 to 30 mph with gusts to 50 mph, increasing to 35 to 40 mph with gusts to 60 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 to trace 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.