THIS AVALANCHE ADVISORY EXPIRED ON March 17, 2015 @ 7:30 am
Avalanche Advisory published on March 16, 2015 @ 7:30 am
Issued by Andy Anderson - Tahoe National Forest

MODERATE avalanche danger will exist at all elevations and on all aspects on slopes 37 degrees and steeper. Human triggered loose wet avalanches remain possible today. Some wet slab avalanches may also become possible on isolated terrain features where wet snow exists above an impermeable bed surface. Since most of the snow has melted away from the SE-S-SW-W aspects, wet snow instabilities on these aspects will remain limited to the isolated slopes that still have snow cover.

2. Moderate

?

Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

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

Last night's cloud cover and warm temperatures should have prevented the snowpack from undergoing much of a refreeze. The snowpack has not been through a solid refreeze for at least 3 nights now. As the day warms up, expect to find wet snow in any areas where snow exists. Human triggered loose wet avalanches will remain possible today on all aspects on slopes 37 degrees and steeper. Since most of the snow has melted away from the SE-S-SW-W aspects, wet snow instabilities will remain confined to the isolated areas where snow cover exists on these aspects. NW-N-NE-E aspects hold the best chances for finding wet snow instabilities today since snow cover remains more consistent on those aspects. Even though these kind of avalanches may not involve enough snow to bury a person, they can push people into areas that would have serious consequences. Keep in mind that secondary terrain hazards such as cliffs and terrain traps hold the potential to greatly magnify consequences of an avalanche that would otherwise be too small to bury or injure a person.

Avalanche Problem 2: Wet Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Even though wet slab avalanches remain unlikely in most places, 3 nights in a row without a solid refreeze, another day of warm weather, and deep wet snow on all aspects where snow exists means that wet slab avalanches may become possible on isolated terrain features today. Since the snowpack has already been through so many melt-freeze cycles this year, the potential for these kind of avalanches should remain confined to isolated areas where the most wet snow exists and where a good bed surface (like a granite slab) exists below the wet snow. Use clues like shin deep wet snow and loose wet snow instabilities to help decide when to leave the snow and head for other activities.

recent observations

Yesterday observations on Andesite Ridge and in the Red Vista area both showed wet snow on all aspects. In both places stepping off of one's skis resulted in sinking into wet snow deeper than the top of one's boots. In some areas in both of these places, wet snow existed all the way to the ground even on some E and NE aspects. Some small skier triggered pinwheels and roller balls did occur on a N aspect at 8600 ft. in the Red Vista area. On Andesite skiers triggered collapses near the summit in areas of rocky terrain where wet snow existed to the ground. In both of these areas the snow coverage has become patchy, and areas of bare ground have even started to appear on the NE aspects.

Weather and CURRENT CONDITIONS
weather summary

The system north of the forecast area should keep the cloud cover over the region for the next few days. Like yesterday temperatures should remain warm with daytime highs in the upper 40's and low 50's above 7000 ft. today and tomorrow. Overnight lows should also remain warmer as long as the cloud cover persists through the night. Last night the overnight lows remained in the upper 30's to upper 40's at all elevations due to the insulating effects of the overnight cloud cover. Yesterday's strong southwest winds started to decrease last night, and they should continue to decrease over then next 36 hours.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 38 to 43 deg. F.
Max. temperature in the last 24 hours: 45 to 50 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 35 to 45 mph
Maximum wind gust in the last 24 hours: 100 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 22 to 42 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy this morning becoming mostly cloudy by mid day. Mostly cloudy skies. Mostly cloudy skies with a slight chance of showers.
Temperatures: 48 to 55 deg. F. 28 to 35 deg. F. 46 to 53 deg. F.
Wind Direction: SW SW SW
Wind Speed: 15 to 20 mph with gusts to 30 mph. 15 to 20 mph with gusts to 30 mph. 10 to 15 mph with gusts to 25 mph.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy this morning becoming mostly cloudy by mid day. Mostly cloudy skies. Mostly cloudy skies with a slight chance of showers.
Temperatures: 42 to 49 deg. F. 26 to 33 deg. F. 45 to 51 deg. F.
Wind Direction: SW SW SW
Wind Speed: 25 to 35 mph with gusts to 55 mph. 20 to 30 mph with gusts to 50 mph. 20 to 30 mph. Gusts to 50 mph, decreasing 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.