THIS AVALANCHE FORECAST EXPIRED ON February 28, 2019 @ 6:57 am
Avalanche Forecast published on February 27, 2019 @ 6:57 am
Issued by Brandon Schwartz - Tahoe National Forest

HIGH avalanche danger continues in near treeline and above treeline areas due to a wind slab avalanche problem. CONSIDERABLE avalanche danger continues below treeline due to a storm slab avalanche problem and isolated wind slabs. Natural and human triggered avalanche activity is expected. Travel in near treeline and above treeline avalanche terrain is not recommended.

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.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Wind slabs are widespread following new snow combined with gale force SW winds. The vast majority of wind slabs exist near treeline and above treeline on NW-N-NE-E-SE aspects. Unstable wind slabs may be encountered to a more isolated extent on other aspects and below treeline due to the strength of the wind. Avalanche size is expected mostly at D2 with up to size D3 possible.

If traveling below treeline, expect that avalanches from above may run into below treeline areas. Pre-plan for low visibility obscuring avalanche start zones overhead. Move around avalanche runout zones with a wide, conservative margin. Do not underestimate potential avalanche size and runout distance.

Avalanche Problem 2: Storm Slab
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High intensity snowfall this morning and rising snow level today will continue to provide the ingredients for a storm slab avalanche problem.  Unstable storm slabs are likely on any wind protected aspect in below treeline to near treeline terrain. Avalanche size up to D2 is expected.

All slopes are suspect at this time and careful, independent evaluation is necessary before making a decision to enter below treeline avalanche terrain. Expect avalanche activity today and be aware of lower angle slopes connected to steeper slopes above or to the side. Get out of existing tracks and gather data. If signs of snow surface cracking or recent avalanche activity are present, make conservative decisions and avoid avalanche terrain.

recent observations

* A natural storm slab avalanche with a crown up to 3 feet occurred yesterday morning below treeline on Andesite Peak (Donner Summit area) (more info).

* Intense blowing snow was observed well below treeline yesterday on Powderhouse Peak (Luther Pass area).

* Wind slabs were present yesterday in most all wind loaded areas but were difficult to trigger in the limited number of areas tested.

* Large fragile cornices were observed yesterday near Picnic Rock (Brockway Summit) and along the summit ridge of Andesite Peak (Donner Summit area). Some of these collapsed from triggers 15 to 20 ft back from the edge.

Weather and CURRENT CONDITIONS
weather summary

The current storm cycle continues with significant snowfall last night for most locations within the forecast area, especially above about 6,800'. High intensity snowfall of around 3 inches per hour is expected this morning along the Sierra Crest. Precipitation intensity is forecast to lull this afternoon and evening, tapering first on the east side of the forecast area. Another round of high intensity snowfall is expected tonight. Gale force ridgetop winds out of the SW will continue all day and into tomorrow. Snow level will rise a bit today with a mix of rain and snow possible around 6,000' to 6,500', especially as precipitation intensity decreases during the midday hours.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 24 to 27 deg. F.
Max. temperature in the last 24 hours: 25 to 28 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 72 mph
Maximum wind gust in the last 24 hours: 128 mph
New snowfall in the last 24 hours: 11 to 20 inches
Total snow depth: 105 to 161 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. Snow in the morning, then snow showers likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Chance of snow showers in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 90%. Mostly cloudy. Snow in the morning, then chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 35 to 41 deg. F. 27 to 32 deg. F. 33 to 38 deg. F.
Mid Slope Winds: Southwest 20 to 30 mph with gusts to 60 mph. Southwest 20 to 30 mph with gusts to 70 mph. Southwest 15 to 30 mph with gusts to 65 mph.
Expected snowfall: 80% probability of 2 to 5 inches. 20% probability of 5 to 8 inches. | SWE = 0.35-0.55 inch. 70% probability of 2 to 5 inches. 30% probability of 5 to 8 inches. | SWE = 0.25-0.50 inch. 80% probability of 3 to 6 inches. 20% probability of 6 to 8 inches. | SWE = 0.20-0.45 inch.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow in the morning, then snow showers likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 100%. Cloudy. Snow showers likely in the evening, then snow after midnight. Snow levels below 7000 feet. Chance of precipitation is 90%. Mostly cloudy. Snow in the morning, then chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 100%.
Temperatures: 27 to 33 deg. F. 24 to 29 deg. F. 28 to 34 deg. F.
Ridge Top Winds: Southwest 45 to 70 mph. Gusts up to 100 mph. Southwest 30 to 45 mph with gusts to 90 mph. Southwest 30 to 45 mph with gusts to 85 mph.
Expected snowfall: 80% probability of 4 to 8 inches. 20% probability of 8 to 10 inches. | SWE = 0.40-0.65 inch. 70% probability of 3 to 6 inches. 30% probability of 6 to 10 inches. | SWE = 0.30-0.55 inch. 80% probability of 3 to 6 inches. 20% probability of 6 to 10 inches. | SWE = 0.25-0.50 inch.
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