THIS AVALANCHE ADVISORY EXPIRED ON February 12, 2015 @ 6:47 am
Avalanche Advisory published on February 11, 2015 @ 6:47 am
Issued by Brandon Schwartz - Tahoe National Forest

Pockets of MODERATE avalanche danger linger above 8,700' on NW-N-NE aspects on slopes 37 degrees and steeper due to persistent slabs. For all other areas, avalanche danger is LOW. A low probability, high consequence scenario has formed with difficult to trigger large avalanches remaining possible in specific areas. Thoughtful deliberate terrain selection is the key to hazard avoidance.

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

Difficult to trigger large avalanches are an ongoing concern above 8,700' on NW-N-NE aspects on slopes 37 degrees and steeper. A weak layer of lower density rounds and rounding faceted snow crystals exists at the base of the recent storm snow in these areas and has been the main instability issue over the past several days. Given the nature of the weak layer and this type of avalanche problem, human triggered avalanche activity remains possible on previously tracked slopes where the necessary trigger point has remained undisturbed. Areas around shallow buried or exposed rocks and along the base of cliff bands represent the most likely trigger points for this avalanche problem.

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

As air temperatures warm, increasing amounts of wet surface snow form, and increasing amounts of snow falls off of rocks and trees, natural and human triggered loose wet avalanches will become possible on all aspects at all elevations. The majority of instability is expected to take the form of roller balls and pinwheels, but small to medium size loose wet avalanches are possible in isolated areas.

recent observations

Recent observations from around the forecast area indicate that the recent storm snow continues to gain strength in the majority of areas. However, a lower density layer of old rounds and rounding faceted snow crystals now buried 2 to 3 feet deep just below the old/new snow interface remains problematic in specific areas. Avalanche activity on slopes 38 degrees and steeper on north aspects off sub ridges on either side of Relay Peak (Mount Rose area) on Feb 7 and Feb 8 along with recent snowpit data from Carson Pass and Waterhouse Peak (Luther Pass area) point to an ongoing persistent slab instability issue on NW-N-NE aspects above 8,700'. Otherwise, generally good stability has been observed over the past few days on E-SE-S-SW-W aspects above 8,700'. Generally good stability has also been observed on all aspects below 8,700' where the weak layer in question was destroyed by rain.

Weather and CURRENT CONDITIONS
weather summary

High pressure is in place over the forecast area. Thin high level cloud cover is expected to dissipate as the day progresses. Air temperatures will continue on a warming trend each day through the end of this week. Light east winds are expected to continue for the next several days. Air temperatures this morning are in the low 30s to mid 40s this morning for areas 8,000' to 9,600'. Inversion conditions exist with air temperatures in the 20s on the mountain valley floors. Maximum daytime air temperatures are forecast to reach the mid 40s to low 50s today for areas above 7,000'.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 30 to 46 deg. F.
Max. temperature in the last 24 hours: 32 to 46 deg. F.
Average wind direction during the last 24 hours: East
Average wind speed during the last 24 hours: 17 mph
Maximum wind gust in the last 24 hours: 27 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 33 to 52 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Partly cloudy skies, becoming sunny. Clear skies. Sunny skies.
Temperatures: 44 to 51 deg. F. 27 to 33 deg. F. 49 to 56 deg. F.
Wind Direction: E E E
Wind Speed: Light winds Light winds Light winds
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Partly cloudy skies, becoming sunny. Clear skies. Sunny skies.
Temperatures: 43 to 50 deg. F. 28 to 35 deg. F. 52 to 58 deg. F.
Wind Direction: E E E
Wind Speed: 10 to 15 mph. Gusts up to 25 mph in the afternoon. 10 to 15 mph. Gusts up to 25 mph in the evening. Light winds
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.