THIS AVALANCHE ADVISORY EXPIRED ON March 21, 2015 @ 6:43 am
Avalanche Advisory published on March 20, 2015 @ 6:43 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 air temperatures several degrees warmer last night at the mid and upper elevations, overnight snow surface refreeze is expected to be decent, but not as thick as 24 hours ago. Patches of cloud cover that existed last night were thin enough to have had little impact on the radiational cooling that is responsible for driving snow surface refreeze when air temperatures are above freezing. As daytime warming progresses today, areas of surface wet snow will form on sun exposed slopes. Increasing cloud cover is expected to slow this process this afternoon to some degree. 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 Mt. Judah (Donner Summit area) indicated that a strong snow surface refreeze had occurred in the area overnight. Snowpit data collected on the E face of Mt. Judah on an E aspect at 8,160' indicated that the snowpack had transitioned to a late spring type structure consisting of melt forms and crusts. The temperature profile was noted as near isothermal. Descending the E face of Mt. Judah at 12:30 pm revealed no signs of wet snow instability. Snow surface conditions at that time consisted of 2 inches of wet snow on top of a 7 inch thick ski and boot supportable melt-freeze crust.

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

High pressure over the region will shift east today as a weak weather system approaches the coast well north of the forecast area. Increasing mid and high level cloud cover and southwest winds increasing to moderate to strong in speed are the main impacts expected today. Light winds last night allowed for air temperature inversion conditions to set up overnight. Remote sensors are reporting air temperatures this morning at 7,000' to 9,600' in the upper 30s to mid 40s with upper 20s to mid 30s on the mountain valley floors. Maximum daytime air temperatures are forecast to reach the mid 40s to upper 50s today for areas above 7,000'. A gradual cooling trend at the upper elevations is expected to begin tomorrow with decreasing southwest winds.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 39 to 45 deg. F.
Max. temperature in the last 24 hours: 54 to 57 deg. F.
Average wind direction during the last 24 hours: East shifting to southwest
Average wind speed during the last 24 hours: 15 mph
Maximum wind gust in the last 24 hours: 26 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.
Friday Friday Night Saturday
Weather: Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies. Partly cloudy skies.
Temperatures: 53 to 59 deg. F. 26 to 33 deg. F. 48 to 54 deg. F.
Wind Direction: SW SW SW
Wind Speed: Light winds increasing to 20 to 25 mph with gusts to 35 mph in the afternoon. 20 to 30 mph with gusts to 50 mph. 20 to 25 mph with gusts to 40 mph, decreasing to 10 to 15 mph with gusts to 25 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies. Partly cloudy skies.
Temperatures: 44 to 51 deg. F. 24 to 31 deg. F. 42 to 48 deg. F.
Wind Direction: SW SW SW
Wind Speed: 10 to 15 mph with gusts to 25 mph, increasing to 30 to 35 mph with gusts to 55 mph in the afternoon. 35 to 45 mph. Gusts to 60 mph increasing to 70 mph after midnight. 35 to 40 mph with gusts to 60 mph, decreasing to 20 to 25 mph with gusts to 35 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 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.