THIS AVALANCHE FORECAST EXPIRED ON February 14, 2019 @ 6:56 am
Avalanche Forecast published on February 13, 2019 @ 6:56 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

The hazard will rise to HIGH avalanche danger today. Large natural avalanches will become likely and human triggered avalanches will be very likely today and tonight. Rain on snow, heavy snow, and gale force winds will create a complicated and dangerous mix of wind slab, storm slab, and loose wet avalanche problems at all elevations. Travel in, near or below avalanche terrain is not recommended. Rain on snow could also cause dangerous roof-avalanches as roofs still holding snow unload. 

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Near Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

4. High

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Below Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Gale force SW winds and new snow will form new wind slabs on top of existing wind slabs. The largest wind slabs should exist on NW-N-NE-E-SE aspects in near and above treeline terrain above 8000 ft where the most new snow accumulates. Wind slabs will also exist on wind-loaded slopes at lower elevations and in some exposed below treeline terrain due to the strength of the winds. Large natural and human-triggered wind slab avalanches will become very likely today and tonight. In areas where rising snow levels allow rain to fall on wind-loaded slopes, wind slab avalanches could involve wet snow and release more easily.

Avalanche Problem 2: Storm Slab
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Rising temperatures and intense snowfall, as well as some existing weaknesses in the snowpack, will cause storm slab avalanches to become very likely today and tonight as well. Storm slab avalanches could occur on any aspect with slopes steep enough to slide. Most storm slabs would involve the newest storm snow but some could entrain older storm snow especially in lower elevation areas on E-SE-S-SW aspects where the older storm snow rests on a thin crust. Like the wind slabs mentioned above rain falling on snow would make storm slabs easier to trigger and could cause them to entrain wet snow and result in larger avalanches.  

Avalanche Problem 3: Loose Wet
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In addition to exacerbating the avalanche problems mentioned above, rain falling on snow will make widespread loose wet avalanche activity very likely. Loose wet avalanches could entrain significant amounts of snow today and tonight and become large enough to bury or injure a person. 

recent observations

* A small wind slab avalanche occurred yesterday in the CHP chutes on Hwy 89 and caught a party who was skinning up. No one was injured. 

* A human-triggered avalanche occurred in less-exposed, lower-elevation terrain on a SE aspect in the burned area near Myers. This slide partially buried a party of 3. It may have failed on a weak layer near a sun crust that formed just before the most recent storm. No injuries were reported.

* Snowpit data from an E aspect above Crystal Bay found a weak layer near a thin crust below the most recent storm snow. Snowpit tests on this layer showed signs of instability that match with the avalanche reported in the Meyers burn area. Snowpit data from a more sheltered SE aspect on Scott's Peak and on a higher elevation SE aspect on Hidden Peak did not find this layer.

* Observations from Centerville Peak, Hidden Peak, Andesite Peak, Scott Peak, and Chocolate Peak all found widespread blowing snow and some wind slab formation. In some areas, these firm wind slabs remained stubborn and hard to produce signs of instability in and in others skier triggered cracking did occur on test slopes. 

* Widespread blowing snow could be seen all along the Sierra Crest and in the Carson Range all day yesterday.

Weather and CURRENT CONDITIONS
weather summary

Gale force SW winds continued through the night and even increased as the winter storm arrived over the area. Precipitation started around midnight for most areas and so far .2 to .7 inches of water has fallen with only about 2 inches of snow accumulating in some areas. Warm air has also moved into the area and snow levels have started to increase. Snow levels should rise to ~ 8000 ft today and stay there until tomorrow afternoon when a cold front brings them back down below 6500 ft. Precipitation and winds should become more intense today through tonight. The forecast calls for another 2 to 5 inches of water that falls as a mix of rain and heavy snow depending on elevation by tomorrow afternoon. Areas above 8000 ft could see 2 to 4 ft of new heavy snow. Overall as the Reno NWS says, "the forecast remains a complicated mess  of rising snow levels, heavy precipitation including rain and snow, and strong ridge and surface winds." For more details check in directly with the Reno NWS.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 28 to 34 deg. F.
Max. temperature in the last 24 hours: 29 to 34 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 65 to 70 mph
Maximum wind gust in the last 24 hours: 127 mph
New snowfall in the last 24 hours: 1 to 2 inches
Total snow depth: 100 to 125 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Mixed rain and snow with mostly rain by the afternoon. Snow levels below 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 100%. Cloudy. Rain and snow. Snow levels 8000 feet. Chance of precipitation is 100%. Cloudy. Rain and snow. Snow levels 8000 feet decreasing to below 7000 feet in the afternoon. Chance of precipitation is 100%.
Temperatures: 36 to 41 deg. F. 30 to 35 deg. F. 35 to 40 deg. F.
Mid Slope Winds: Southwest 30 to 45 mph with gusts to 95 mph. Southwest 30 to 45 mph with gusts to 85 mph. South 30 to 45 mph with gusts to 85 mph.
Expected snowfall: 50% probability of 6 to 12 inches. 50% probability 0 to 6 inches. | SWE = 1.10-1.60 inches. 60% probability of 0 to 5 inches. 40% probability of 5 to 10 inches. | SWE = 0.90-1.35 inches. 70% probability of 5 to 10 inches. 30% probability of 10 to 15 inches. | SWE = 1.05-1.55 inches.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow through the day. Rain in the afternoon. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 100%. Cloudy. Snow and rain. Snow levels 8000 feet. Chance of precipitation is 100%. Cloudy. Rain in the morning. Snow through the day. Snow levels 8000 feet decreasing to below 7000 feet in the afternoon. Chance of precipitation is 100%.
Temperatures: 33 to 38 deg. F. 28 to 33 deg. F. 32 to 38 deg. F.
Ridge Top Winds: Southwest 50 to 70 mph with gusts to 140 mph. Southwest 50 to 70 mph with gusts to 140 mph. Southwest 45 to 60 mph with gusts to 125 mph.
Expected snowfall: 80% probability of 10 to 18 inches. 20% probability of 6 to 10 inches. | SWE = 2.05-2.05 inches. 80% probability of 7 to 14 inches. 20% probability of 15 to 22 inches. | SWE = 1.00-1.50 inches. 70% probability of 7 to 15 inches. 30% probability of 16 to 22 inches. | SWE = 1.10-1.60 inches.
Disclaimer

This avalanche forecast is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This forecast 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 forecast applies only to backcountry areas outside established ski area boundaries. This forecast describes general avalanche conditions and local variations always occur. This forecast expires 24 hours after the posted time unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the avalanche forecast call (530) 587-3558 x258