THIS AVALANCHE ADVISORY EXPIRED ON April 10, 2013 @ 7:00 am
Avalanche Advisory published on April 9, 2013 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

Near and above treeline, very isolated pockets of MODERATE avalanche danger exist on E-SE-S-SW-W-NW aspects on slopes 35 degrees and steeper due to small shallow wind slabs. For all other areas, avalanche danger remains LOW.

2. Moderate

?

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

1. Low

?

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

1. Low

?

Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

The NE winds have moved snow from the N-NE-E aspects to the SE-S-SW-W-NW aspects. The wind slabs formed by this wind loading should remain fragile today. Due to the small amount of snow available for transport these slabs should also remain small and not extend very far away from the near and above treeline exposed ridglines. On the S-SW-W aspects this wind transported snow will accumulate on exposed ground in many areas since much that snow has already melted. Cross loaded NW and SE aspects near and above treeline will hold the largest and most fragile of these small wind slabs. Some very small and isolated wind slabs could also exist on other aspects. Small human triggered avalanches remain possible today in isolated areas. Even though these slides should remain small they could still push a person into an area with other consequences or could become more serious in areas where terrain traps exist.

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

Frozen crusts with 2-5 inches of cold snow above them will allow loose snow sluffs to remain possible today. These should remain small and not entrain enough snow to cause problems in most areas. In a few isolated areas, these sluffs may be able to knock a person off balance of alter the course of person. Slopes steeper than 37 degrees above 7500 ft. with cold new snow on them hold the best potential for these small sluffs.

recent observations

Some small wind slabs up to 1 ft. deep existed on SE aspects near Elephant's Back on Carson Pass yesterday. The weight of a skier on tests slopes where these wind slabs existed did cause cracking and small test slope failures. These slabs quickly diminished in size as the distance from the ridgeline increased. The largest of these slabs extended about 15 ft from the exposed Elephant's Back ridgeline. It tapered down to only 3-4 inhces thick by its end. The NE winds had already scoured all of the snow away from many of the exposed N-NE-E aspects by mid-day leaving behind a frozen icy crust. On the more sheltered N-NE aspects in this area, ski cuts caused ski width wide sluffs as the 2-4 inches of new snow slid down the icy crust below it. In the Mt. Rose area, ski cuts on steep mid elevation partly sheltered NE aspects did release small wind slabs 2-6 inches deep in morning. On more exposed N-NE facing slopes, the NE winds had scoured the new snow and wind slabs away.

Weather and CURRENT CONDITIONS
weather summary

Strong northeast winds in the 40-50 mph range with gusts approaching 85 mph should continue through tonight as a high pressure ridge begins to form over the area. This northerly flow should help keep temperatures from warming up too much today. The forecast calls for daytime highs in the 30's above 7000 ft. By tomorrow the high pressure should cause the northeast winds to begin decreasing and temperatures could climb into the mid 40's to mid 50's above 7000 ft.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 14-21 deg. F.
Max. temperature in the last 24 hours: 22-32 deg. F.
Average wind direction during the last 24 hours: Northeast
Average wind speed during the last 24 hours: 35-55 mph
Maximum wind gust in the last 24 hours: 81 mph
New snowfall in the last 24 hours: up to 1 inches
Total snow depth: 44-81 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Tuesday Tuesday Night Wednesday
Weather: Sunny Clear Sunny with high clouds increasing late in the day
Temperatures: 37-42 deg. F. 25-30 deg. F. 50-55 deg. F.
Wind Direction: Northeast Northeast East shifting to the north in the afternoon
Wind Speed: 20-35 mph with gusts to 50 mph 20-35 mph with gusts to 50 mph 20-30 mph with gsuts to 45 mph decreasing to 10-15 mph with gusts to 25 mph in the afternoon
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Sunny Clear Sunny with high clouds increasing late in the day
Temperatures: 33-39 deg. F. 22-29 deg. F. 45-50 deg. F.
Wind Direction: Northeast Northeast Northeast shifting to the north in the afternoon
Wind Speed: 40-45 mph with gusts to 70 mph increasing to 50-55 mph with gusts to 85 mph in the afternoon 50-60 mph with gusts to 85 mph 40-45 mph with gusts to 65 mph decreasing to 20-25 mph with gusts to 40 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.