THIS AVALANCHE ADVISORY EXPIRED ON January 5, 2016 @ 6:56 am
Avalanche Advisory published on January 4, 2016 @ 6:56 am
Issued by Brandon Schwartz - Tahoe National Forest

For most of today, LOW avalanche danger is expected to continue for all elevations and aspects. Minor wind slabs not large enough to bury or injure a person remain an issue near and above treeline on NW-N-NE aspects. As additional snowfall accumulates, wind slab size will increase and avalanche danger is expected to increase to MODERATE danger sometime late today or tonight with a further increase in avalanche danger expected during the day tomorrow.

2. Moderate

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

2. Moderate

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

1. Low

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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
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Small wind slabs not large enough to bury or injure a person linger near and above treeline on NW-N-NE aspects. These slabs formed Saturday from S winds transporting old snow on the ground and creating new wind loading in lee areas. These slabs were most reactive on Saturday, but tiny slabs 2 to 6 inches deep and up to 6 feet wide remained reactive to skier triggering in some areas yesterday.

Wind slabs will become larger and more dangerous as new snow is wind loaded in lee areas today and tonight. At some point between late this afternoon and tomorrow morning these slabs are expected to become large enough to bury or injure a person. At that time, active measures beyond normal caution will be necessary to manage the hazard. Take a moment to discuss with your partner and identify in the immediate surroundings the areas where these wind slabs are most likely to exist. Make and execute a plan for specifically avoiding suspect areas.

recent observations

Observations made and received yesterday from Mt. Tallac (Desolation Wilderness area), Silver Peak (Pole Creek area), and from Andesite Ridge and Red Mountain (Donner Summit area) indicated improved wind slab stability over the previous day with a small amount of lingering instability associated with tiny wind slabs. In the vast majority of wind loaded areas tested, no signs of instability were observed. In isolated areas, a few skier triggered cracks and wind slabs up to 6 feet wide and up to 6 inches deep were triggered, but only moved a few feet down slope. These slabs were enough to knock a person off balance, but too small to bury or injure a person (Size D1).

Snow surface warming was noted on all aspects yesterday in areas below 7,000-7,500'. Roller balls were observed on steep low elevation slopes, but nothing in the way of significant loose wet instability was observed.

Weather and CURRENT CONDITIONS
weather summary

 A splitting weather system moving into the region will bring cloud cover, scattered snow showers, and moderate speed S winds to the forecast area today. Best case scenario looks like 2 inches of snowfall today along the Sierra Crest, with less than that likely in many areas. Maximum daytime air temperatures above 7,000' are forecast to reach the mid 20s to mid 30s. A second more consolidated storm system will move into the forecast area tonight. This storm holds potential for significant new snow accumulation and the NWS Reno has issued a Winter Weather Advisory beginning at 2am tomorrow. Maximum daytime air temperatures are expected to be a few degrees colder tomorrow with S winds increasing to gale force in speed over the upper elevations.

 

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 24 to 30 deg. F.
Max. temperature in the last 24 hours: 30 to 37 deg. F.
Average wind direction during the last 24 hours: S
Average wind speed during the last 24 hours: 17 mph
Maximum wind gust in the last 24 hours: 39 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 46 to 53 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Cloudy skies with scattered snow showers. Cloudy skies with scattered snow showers. Cloudy skies with snow showers in the morning. Snow in the afternoon.
Temperatures: 29 to 36 deg. F. 18 to 25 deg. F. 25 to 32 deg. F.
Wind Direction: S S S
Wind Speed: 10 to 15 mph with gusts to 25 mph. 15 to 20 mph with gusts to 25 mph. Gusts increasing to 35 mph after midnight. 15 to 20 mph with gusts up to 35 mph in the afternoon.
Expected snowfall: Up to 2 in. Up to 2 in. 4 to 10 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Cloudy skies with scattered snow showers. Cloudy skies with snow showers. Cloudy skies with snow showers in the morning. Snow in the afternoon.
Temperatures: 25 to 32 deg. F. 17 to 24 deg. F. 22 to 29 deg. F.
Wind Direction: S S S
Wind Speed: 20 to 30 mph with gusts to 45 mph. 30 to 35 mph with gusts to 50 mph, increasing to 55 to 60 mph with gusts to 90 mph after midnight. 55 to 60 mph with gusts to 90 mph.
Expected snowfall: Up to 2 in. Up to 2 in. 5 to 12 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.